bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of net section damage on creep crack growth
Authors: Nishida K , Nikbin K M , Webster G A
Published: July 2007

Fracture mechanics concepts for describing creep crack growth in terms of ductility exhaustion in a process zone at the crack tip are reviewed and extended to include damage accumulation in the ligament ahead of a crack. Applications are considered which show that net section damage has most influence for short cracks and plane stress conditions where significant damage can develop in the uncracked ligament. It is shown that, under plane strain loading, insufficient ligament damage occurs during the crack growth phase for it to have an appreciable effect on failure times. A method is also presented for accounting for the influence of an incubation period prior to the onset of cracking and for making residual life estimates.
The use of a bree simulation to investigate strain accumulation in 316 stainless steel at temperatures between room temperature and 500°c
Authors: Brookfield D J , Moreton D N
Published: July 2007

This paper details tests undertaken to determine the 1 per cent strain accumulation boundary in stainless steel type 316 strip subjected to constant axial tension and a cyclic change of curvature. Boundaries are obtained for temperatures between 300 and 500°C. These are compared with two design rules, both of which are shown to be conservative. Additionally, the temperature at which the transition from the characteristic room temperature behaviour of continued ratchetting to the ‘shakedown’ observed at elevated temperatures is investigated. Results obtained indicate that this transition temperature is influenced by the magnitude of the applied stresses.
On the effect of key edge shape on keyway edge stresses in shafts in torsion
Authors: Fessler H , Appavoo T
Published: July 2007

Two-dimensional, photoelastic tests of cross-sections of two keyed shafts with 13 different shapes of keys showed that rounded edges of keys give lower stress concentrations in the shaft than chamfered edges. Stress concentrations are reduced by making both rounding radii and chamfers larger than the key way fillet radius.

Making the key a sliding fit in the keyway allows significant relative movement and produces lower stress concentrations than the usual interference fits.

Boussinesq's theoretical solution for stresses near a concentrated edge load has been successfully used for direct calibration of small photoelastic models.
Mechanical analysis of an annular plate subject to a transverse concentrated load
Authors: Strozzi A
Published: July 2007

The periphery deflection in an annular plate clamped along its inner edge and loaded at its outer boundary by a transverse concentrated force are studied via a series solution. The corrected expressions for the series coefficients are presented. The series convergence is accelerated via a simple technique. Approximate methods are proposed to account for the compliant clamp and shear strain effects on the plate deflections, and they are validated against simplified theoretical models.
Strain distribution in steel base plates under eccentric loads
Authors: Paramasivam P , Thambiratnam D P
Published: July 2007

Experiments have been conducted on steel column base plates subjected to eccentric loads and the strain distributions in the base plates at various stages of loading have been determined. The thickness of the base plate and the eccentricity of load have been treated as parameters. Test results for the maximum bending strains, which always occurred at the column–base plate junction on the side of the load, compare reasonably well with those from a finite element analysis. However, the present results for the bending strains in the cantilever portions of the base plates which failed by yielding are greater than those obtained from classical theory, which is, therefore, seen to be conservative for these cases. Longitudinal and lateral strain distributions, strain contour plans, maximum bending strain variation with load, and interaction diagrams are presented and the results discussed. From these results it is evident that flexible base plates, especially when loaded at higher eccentricities, behave somewhat differently from what is assumed in classical methods.
Damage development in composites: Mechanisms and modelling
Authors: Talreja R
Published: July 2007

This paper presents first a review of the mechanisms of damage and its development in composite materials subjected to mechanical loads. The materials considered are thermosetting polymers reinforced with short or long fibres of glass or carbon. Laminates with woven fabric are also considered. A discussion regarding how the essential features of the damage mechanisms may be incorporated in a modelling approach is then given. Two basically different but complementary approaches, namely, micromechanics modelling and continuum damage modelling, are described. The present author's own approach using the internal variables concept is discussed at some length, and the predictions of elastic property degradation given by it are illustrated by experimental data.

This paper is an updated and expanded version of a previous paper written by the author (32).
The fatigue behaviour of fibrous composite materials
Authors: Curtis P T
Published: July 2007

The fatigue behaviour of high performance continuous fibre reinforced composite materials based on organic matrices has been reviewed. Methods of performing fatigue tests are discussed. Fatigue damage development processes are reviewed for typical unidirectional and laminated materials and fatigue performance compared for different materials. The effects of stress concentrators and environmental exposure are considered and the use of alternative forms of composite such as woven materials discussed. A comparison with the fatigue of metals is made.
Online stochastic control of dimensional quality in multistation manufacturing systems
Authors: Djurdjanovic D , Ni J
Published: July 2007

In the current paper, a control law is devised for flexible tooling element adjustments in a multistation manufacturing system based on the in-process product measurements and the state-space model of dimensional error flow through this system. The control law is devised so that the dimensional product quality at the end of the line is as close to the nominal as possible in the least squares sense, taking into account the measurement and process noise, as well as the accuracy of actuation of flexible tooling elements. The condition of controllability of product quality is introduced and dimensional quality variations of the product with and without the newly introduced stochastic quality control law are compared. It is proven that the newly proposed control algorithm reduces variations of dimensional product errors and that the controllability condition is beneficial to both the expected product quality as well as for its variations. Capabilities of the newly proposed method for stochastic control of dimensional quality in multistation manufacturing systems are illustrated in an example of a machining system used for the manufacturing of an automotive cylinder head by a major automotive manufacturer.
Non-linear modelling using central composite design to predict green sand mould properties
Authors: Parappagoudar M B , Pratihar D K , Datta G L
Published: July 2007

The quality of cast products in green sand moulds is largely influenced by the mould properties, such as green compression strength, permeability, hardness, and others, which depend on the input (process) parameters. The relationships of these properties with input parameters such as sand grain size and shape, amount of binder and water, number of strokes in ramming, etc., are complex in nature. Design of experiments (DOE) with response surface methodology was used to develop the said input-output relationships. An attempt was also made to relate green compression strength to mould hardness. Moreover, responses such as permeability, hardness, and green compression strength were separately expressed as functions of bulk density. The relationship between green compression strength and permeability in a clay-bonded sand system is generally reverse in nature. To ensure good-quality castings, the green sand mould is required to have both adequate permeability as well as strength. This situation will lead to the formulation of a multiobjective optimization problem. A Pareto optimal front of solutions was developed for strength and permeability, using a multiobjective optimization tool - the so-called non-dominated sorting genetic algorithm (NSGA). The Pareto optimal front contains a number of optimal solutions. One optimal solution differs from another on account of the fact that different sets of weightages are given to the objective functions. Thus, the user has to select one set of optimal solutions out of different available sets.
Optimal proportional-integral-derivative control of shape memory alloy actuators using genetic algorithm and the Preisach model
Authors: Ahn K. K. , Nguyen B. K.
Published: July 2007

Shape memory alloy (SMA) actuators, which have the ability to return to a predetermined shape when heated, have many potential applications in aeronautics, surgical tools, robotics, and so on. Although the number of applications is increasing, there has been limited success in precise motion control owing to the hysteresis effect of these smart actuators. The present paper proposes an optimization of the proportional-integral-derivative (PID) control method for SMA actuators by using genetic algorithm and the Preisach hysteresis model.

In this work, the numerical Preisach model with geometrical interpretation is used for hysteresis modelling of SMA actuators. This model is then incorporated in a closed-loop PID control strategy. The optimal values of PID parameters are determined by using genetic algorithm to minimize the mean squared error between desired output displacement and simulated output. This is used to reduce hysteresis effects and improve accuracy for the displacement of SMA actuators.
On a new methodology for the design of structure reduced multivariable controllers
Authors: Nobakhti A , Wang H , Kookos I
Published: July 2007

This paper proposes a new methodology for the design of multivariable controllers with a reduced structure. The structure of a multivariable controller may be defined in several ways. In this paper it is defined as the number of the input to output connections of the controllers. Based on this structure definition, a generic cost function is determined where both the structure of the controller and the performance of the resulting closed loop system appear as minimization terms. It has been shown that there exists an optimal weighting such that the optimization of the weighted sum of these two terms will always result in a unique reduced structure controller. The methodology is then successfully applied to the model of the ALSTOM (ALSTOM Power Technology Centre, formerly GEC ALSTHOM) gasifier challenge problem, which is a difficult multivariable system to control.
Design of optimal robust fixed-structure controllers using the quantitative feedback theory approach
Authors: Halikias G. D. , Zolotas A. C. , Nandakumar R
Published: July 2007

A simple optimization algorithm is proposed for designing fixed-structure controllers for highly uncertain systems. The method can be used to automate the loop-shaping step of the quantitative feedback theory (QFT) design procedure and guarantees robust stability and performance to the feedback loop for all parameters in the plant's uncertainty set. To avoid over-designing the system, the algorithm can be used to minimize either the asymptotic gain, the open-loop crossover frequency or the 3 dB bandwidth of the closed-loop system (nominal or worst case). The proposed algorithm is illustrated with a design example involving a hydraulic actuator, carried out within a computer aided design (CAD) environment (‘StdQFT’ toolbox) which has been developed by the authors. Some preliminary results of this work appeared in 2002 [1].
Parameter-dependent adaptive H∞ control design for a class of linear parameter-varying systems using polynomially parameter-dependent quadratic functions
Authors: Karimi H. R.
Published: July 2007

This paper presents a new technique to design a parameter-dependent adaptive H∞ control for a class of linear parameter-varying (LPV) systems. It is assumed that the statespace matrices affinely depend on parameters that are not measurable in real-time for the control process. By introducing a Hamiltonian-Jacobi-Isaac (HJI) function and using the vector projection method, a sufficient condition is first established for the stability analysis problem in terms of a parameter-dependent linear matrix inequality (LMI). Then, by means of the polynomially parameter-dependent quadratic (PPDQ) functions, a parameter-independent LMI-based condition is derived, which enables an explicit expression to be found of the parameter-dependent adaptive H∞ control that guarantees both robust asymptotic stability and a prescribed level of disturbance attenuation for the system. Two numerical examples are given to illustrate the applicability of the proposed design approach.
A new adaptive learning algorithm for robot manipulator control
Authors: Hasan A. T. , Hamouda A. M. S. , Ismail N , Al-Assadi H M A A
Published: July 2007

This paper is devoted to the development and implementation of neural network technology to solve the inverse kinematics problems for serial robot manipulators, given the desired Cartesian path of the end effector of the manipulator in a free-of-obstacles workspace. Offline smooth geometric paths in the joint space of the manipulator are obtained.

The proposed technique does not require any prior knowledge of the kinematics model of the system being controlled; the main idea of this approach is the use of an artificial neural network to learn the robot system characteristics rather than having to specify an explicit robot system model.

Since one of the most important problems in using artificial neural networks is the choice of the appropriate network configuration, two different configurations were compared; they were trained to learn the desired set of joint angles positions from a given set of end effector positions.

The generality and efficiency of the proposed algorithm are demonstrated through simulations of a general six-degrees-of-freedom serial robot manipulator.
Performance bounds analysis for hybrid estimation
Authors: Yang Xiaojun , Xing Keyi , Shi Kunlin , Pan Quan
Published: July 2007

The Cramér-Rao lower bound, CRLB, is important for the performance analysis of a filter. The theoretical CRLB for hybrid estimation requires enumeration of all possible model sequences. In the current paper a computationally tractable estimation of CRLB for hybrid estimation is proposed, which makes use of a subset of sequence hypotheses to approximate the theoretical bound. This approach provides a trade-off between computation and tightness of the estimated CRLB. Thus, the bound is an improvement of the simple ‘conservative’ bound, which only includes a correct model sequence. To compute the estimation of the Cramér-Rao bound for a non-linear system, a Monte Carlo approximate method is introduced. The subset of model sequence hypotheses is achieved through sampling and the expectation integrals are approximated by means of sampling based on Monte Carlo simulation of the particle filtering. The bound is shown a tighter bound than the ‘conservative’ bound for the state estimation by simulation.
Mobile robot navigation algorithm using a vector-based topological map and virtual Jacobian
Authors: Choi Gyu-Jong , Jung Young-Seok , Ahn Doo-Sung
Published: July 2007

In this paper, a vector-based topological map is to be built consisting of available directions (moving directions) and the distances between nodes. This map represents the whole environment as a skeleton, using nodes similar to vectors independent of geometrical information of obstacles. To build a vector-based topological map, the following are developed: (a) acquisition of reliable range values using local minimum values, (b) fuzzy inference system (FIS) for extracting available directions, and (c) collision avoidance using virtual Jacobians. First, only local minimum values are used among the range of sensor values in order to decrease the effect of specular reflection and calculate available directions using the FIS. Specially, the number of consequent membership functions is determined as the number of obstacle orientations around a mobile robot, enabling the mobile robot to find available directions independently of the geometrical information of obstacles. Finally, to avoid collisions, a virtual Jacobian method is used because a vector-based topological map does not include the geometrical information about obstacles. The proposed algorithms have been verified in the simulation and implemented on a robot in the real environment.
Generalized missile guidance laws against manoeuvring targets
Authors: Yanushevsky R. T.
Published: July 2007

A new class of guidance laws is developed on the basis of the Lyapunov method. The proposed new guidance laws improve the effectiveness of the proportional navigation (PN) law against manoeuvring targets. They augment the PN law which is a part of these laws. Analytical expressions of the new guidance laws for the generalized three-dimensional engagement model are presented. By considering separately the missile longitudinal and lateral motions, the expressions for its radial and lateral accelerations are obtained. The new guidance laws can be utilized for missiles with thrust control as well as for many types of existing missile without throttlable engines.
Variable structure attitude manoeuvre control and active vibration damping of three-axis-stabilized flexible spacecraft
Authors: Hu Qinglei
Published: July 2007

This paper presents a dual-stage control system design method for the three-axis-rotational manoeuvre and vibration stabilization of a spacecraft with flexible appendages embedded with piezoceramics as the sensor and actuator. In this design approach, the attitude control system and vibration suppression were designed separately using a lower-order model. The design of the attitude controller was based on the variable structure control (VSC) theory, leading to a discontinuous control law. This controller accomplishes asymptotic attitude maneouvring in the closed-loop system and is insensitive to the interaction of elastic modes and uncertainty in the system. The advantage of this dual-stage approach is that once the desired orientation is attained under the VSC law, only the elastic motion is governed by the decoupled linear second-order systems describing elastic dynamics. To this end, modal velocity feedback and optimal positive position feedback control methods are presented and compared for actively damping the elastic oscillations using piezoelectric materials as an additional sensor and actuator bonded on the surface of the flexible appendages. In addition, a special configuration of actuators for three-axis attitude control is also investigated: the pitch attitude controlled by a momentum wheel and the roll/yaw control achieved by on-off thrusters, which is modulated by the pulse width-pulse frequency modulation technique to construct a proper control torque history. Numerical simulations are performed to show that the rotational manoeuvre and vibration suppression are accomplished in spite of the presence of disturbance torque and parameter uncertainty.
A novel approach to dynamic modelling of polymer extrusion for improved process control
Authors: McAfee M , Thompson S
Published: July 2007

Polymer extrusion is a complex process and the availability of good dynamic models is key for improved system operation. Previous modelling attempts have failed adequately to capture the non-linearities of the process or prove too complex for control applications. This work presents a novel approach to the problem by the modelling of extrusion viscosity and pressure, adopting a grey box modelling technique that combines mechanistic knowledge with empirical data using a genetic algorithm approach. The models are shown to outperform those of a much higher order generated by a conventional black box technique while providing insight into the underlying processes at work within the extruder.
Suppression of base vibrations and tracking of the tip of an inverted pendulum using sliding mode control and quantitative feedback theory
Authors: Rajapakse N. I. , Happawana G. S. , Hurmuzlu Y
Published: July 2007

This paper presents a robust control method, combining sliding mode control (SMC) and quantitative feedback theory (QFT) to track the tip of an inverted pendulum, subject to base excitation. A non-linear inverted pendulum (IP) model is considered to analyse tracking control characteristics through computer simulation in order to demonstrate the effectiveness of the proposed control methodology. The sliding mode control is used to track the trajectory of the tip of the inverted pendulum. However, when the system enters into sliding regime, chattering occurs due to switching delays as well as base vibrations. The chattering is eliminated with the introduction of QFT inside the boundary layer to ensure smooth tracking. Problems with noise amplification, resonances, presence of uncertainties, and unmodelled high-frequency dynamics can largely be avoided with the use of QFT over other optimization methods. In addition, the QFT design methodology guides design evolution rather than replacing human intervention as would appear to be the case in some control synthesis methodologies.
Sensitivity bond graph approach to multiple fault isolation through parameter estimation
Authors: Samantaray A. K. , Ghoshal S. K.
Published: July 2007

In model-based quantitative multiple fault detection and isolation (FDI), fault disambiguation is based on parameter estimation. In this paper, the fault hypothesis is generated by evaluating a set of analytical redundancy relations (ARRs) and parameter values corresponding to the unstructured part of the fault subspace are estimated by minimizing a function of the ARRs. Process and measurement uncertainties are handled by using a passive approach for robust FDI. Bond graph modelling is used to describe process models and to derive the ARRs. The bond graph model of the process is differentially causalled and it is then converted into a diagnostic bond graph form. The diagnostic bond graph is further converted into its corresponding sensitivity bond graph form, which gives the residual sensitivity to parametric changes. The developed algorithm provides quicker fault isolation because only a few parameters are estimated and it does not need several model simulations, thereby making it suitable for real-time process supervision.
Crack closure stress estimation by decodable marker banding techniques and comparison of results with electron fractographic technique
Authors: Prakash R V , Sunder R
Published: July 2007

A specially programmed marker load sequence was designed that permits unambiguous measurement of crack opening and crack closure stress from marker band spacing using both optical and scanning electron fractography. Crack growth tests using programmed marker loading sequence were carried out on single edge notch tension specimens made out of Al-Cu alloy 2014-T3 (BS: L73 equivalent) from crack initiation to failure and the fracture surface examined under optical and electron microscope. Reproducible marker band patterns on the fatigue fracture surface could be obtained using this method. Measured crack closure/opening stress values are observed to be consistent with known material behaviour. The marker banding technique can be applied over wider crack growth rate ranges compared to striation measurement technique, which is restricted to a small range of crack growth rate and in select materials. Quantitative fractography of the marker bands reveals a degree of load interaction under variable amplitude loading that requires further examination.
Experimental Study on Gas-phase Ionization Process for Ion Attachment Mass Spectrometry
Authors: Chen Lei , Suzuki Yaeko , Hara Kenji , Korenaga Takashi
Published: July 2007

In this study, in order to investigate the mechanism of Li+ attachment process, dimethylarsinic acid (DMAA) was detected by selective-ion monitoring mode of ion attachment mass spectrometry (IAMS) and the Li+ binding energy of N2 and DMAA was also calculated. The results indicated the possibility of the transfer of Li+ from N2Li+ to DMAA in IAMS analysis. This study could contribute to the development and application of IAMS technique.
Expression of Plasmid DNA Released from DNA Conjugates of Gold Nanorods
Authors: Horiguchi Yukichi , Niidome Takuro , Yamada Sunao , Nakashima Naotoshi , Niidome Yasuro
Published: July 2007

Pulsed-laser irradiation induced the release of plasmid DNA from conjugates of DNA and gold nanorods (GNRs). Gel electrophoresis indicated that 1% of the plasmid DNA conjugated with GNRs was released from the conjugates. In vitro assay indicated that 0.5% of plasmid DNA was active.
The continuous ranked probability score for circular variables and its application to mesoscale forecast ensemble verification
Authors: Grimit E. P. , Gneiting T. , Berrocal V. J. , Johnson N. A.
Published: July 2007

An analogue of the linear continuous ranked probability score is introduced that applies to probabilistic forecasts of circular quantities, such as wind direction. This scoring rule is proper and thereby discourages hedging. The circular continuous ranked probability score reduces to angular distance when the forecast is deterministic, just as the linear continuous ranked probability score generalizes the absolute error. Furthermore, the circular continuous ranked probability score provides a direct way of comparing deterministic forecasts, discrete forecast ensembles, and post‐processed forecast ensembles that can take the form of circular probability density functions.

The circular continuous ranked probability score is used in this study to compare predictions of 10 m wind direction for 361 cases of mesoscale, short‐range ensemble forecasts over the North American Pacific Northwest. Simple, calibrated probability forecasts based on the ensemble mean and its forecast error history over the period outperform probability forecasts constructed directly from the ensemble sample statistics. These results suggest that short‐term forecast uncertainty is not yet well predicted at mesoscale resolutions near the surface, despite the inclusion of multi‐scheme physics diversity and surface boundary parameter perturbations in the mesoscale ensemble design. Copyright © 2006 Royal Meteorological Society
A baroclinic instability test case for atmospheric model dynamical cores
Authors: Jablonowski Christiane , Williamson David L.
Published: July 2007

A deterministic initial‐value test case for dry dynamical cores of atmospheric general‐circulation models is presented that assesses the evolution of an idealized baroclinic wave in the northern hemisphere. The initial zonal state is quasi‐realistic and completely defined by analytic expressions which are a steady‐state solution of the adiabatic inviscid primitive equations with pressure‐based vertical coordinates. A two‐component test strategy first evaluates the ability of the discrete approximations to maintain the steady‐state solution. Then an overlaid perturbation is introduced which triggers the growth of a baroclinic disturbance over the course of several days.

The test is applied to four very different dynamical cores at varying horizontal and vertical resolutions. In particular, the NASA/NCAR Finite Volume dynamics package, the National Center for Atmospheric Research spectral transform Eulerian and the semi‐Lagrangian dynamical cores of the Community Atmosphere Model CAM3 are evaluated. In addition, the icosahedral finite‐difference model GME of the German Weather Service is tested. These hydrostatic dynamical cores represent a broad range of numerical approaches and, at very high resolutions, provide independent reference solutions. The paper discusses the convergence‐with‐resolution characteristics of the schemes and evaluates the uncertainty of the high‐resolution reference solutions. Copyright © 2006 Royal Meteorological Society
The validity of serum levels as a surrogate measure of systemic exposure to metal ions in hip replacement
Authors: Daniel J. , Ziaee H. , Pynsent P. B. , McMinn D. J. W.
Published: July 2007

Metal ions generated from joint replacements are a cause for concern. There is no consensus on the best surrogate measure of metal ion exposure. This study investigates whether serum and whole blood concentrations can be used interchangeably to report results of cobalt and chromium ion concentrations.

Concentrations of serum and whole blood were analysed in 262 concurrent specimens using high resolution inductively-coupled plasma mass-spectrometry. The agreement was assessed with normalised scatterplots, mean difference and the Bland and Altman limits of agreement.

The wide variability seen in the normalised scatterplots, in the Bland and Altman plots and the statistically significant mean differences between serum and whole blood concentrations suggest that they cannot be used interchangeably. A bias was demonstrated for both ions in the Bland-Altman plots. Regression analysis provided a possible conversion factor of 0.71 for cobalt and 0.48 for chromium. However, even when the correction factors were applied, the limits of agreement were greater than ±67% for cobalt and greater than ±85% for chromium, suggesting that serum and whole blood cannot be used interconvertibly. This suggests that serum metal concentrations are not useful as a surrogate measure of systemic metal ion exposure.
In vivo movement analysis of the patella using a three-dimensional computer model
Authors: Yamada Y. , Toritsuka Y. , Horibe S. , Sugamoto K. , Yoshikawa H. , Shino K.
Published: July 2007

We used three-dimensional movement analysis by computer modelling of knee flexion from 0° to 50° in 14 knees in 12 patients with recurrent patellar dislocation and in 15 knees in ten normal control subjects to compare the in vivo three-dimensional movement of the patella. Flexion, tilt and spin of the patella were described in terms of rotation angles from 0°. The location of the patella and the tibial tubercle were evaluated using parameters expressed as percentage patellar shift and percentage tubercle shift. Patellar inclination to the femur was also measured and patellofemoral contact was qualitatively and quantitatively analysed.

The patients had greater values of spin from 20° to 50°, while there were no statistically significant differences in flexion and tilt. The patients also had greater percentage patellar shift from 0° to 50°, percentage tubercle shift at 0° and 10° and patellar inclination from 0° to 50° with a smaller oval-shaped contact area from 20° to 50° moving downwards on the lateral facet.

Patellar movement analysis using a three-dimensional computer model is useful to clearly demonstrate differences between patients with recurrent dislocation of the patella and normal control subjects.
Medium-term results of the Bernese periacetabular osteotomy in the treatment of symptomatic developmental dysplasia of the hip
Authors: Garras D. N. , Crowder T. T. , Olson S. A.
Published: July 2007

We studied the medium-term outcome of the Bernese periacetabular osteotomy in 52 patients (58 hips) with symptomatic developmental dysplasia of the hip and a mean age of 37.6 years (13 to 48).

The operations were performed between 1993 and 2005 by the senior author with a mean follow-up of 66.7 months (13 to 153). There were 42 women (47 hips) and ten men (11 hips). Of these patients, 24 (30 hips) had an osteotomy on the right side and 22 (28 hips) on the left. Six patients had bilateral operations. The clinical outcome was assessed using the modified Merle d’Aubigne scale, and pre- and post-operative radiological evaluation using the modified Tonnis osteoarthritis score, the centre-edge angle, the acetabular index, the status of Shenton’s line, and the cross-over sign.

The mean centre-edge angle and the acetabular index were 14° (2° to 34°) and 23.6° (0° to 40°) before operation, and 36.6° (16° to 72°) and 7.9° (0° to 28°) after, respectively (p < 0.001, analysis of variance (ANOVA)). Shenton’s line was intact in 23 hips (39.6%) before operation and in 48 hips (82.8%) after. The cross-over sign was present in 31 hips (53.4%) before and in three hips (5.2%) after operation (p < 0.001, ANOVA). The total Merle d’Aubigne clinical score improved from a mean of 12.6 (9 to 15) to 16.0 (12 to 18) points (p < 0.001, ANOVA). Only four hips required subsequent total hip replacement.

Our results indicate that the Bernese periacetabular osteotomy provides good symptomatic relief for patients with little to no arthritis (Tonnis type 0 or 1) with an underlying deformity that can be corrected to a position of a stable, congruent hip joint.
Insufficient duration of venous thromboembolism prophylaxis after total hip or knee replacement when compared with the time course of thromboembolic events
Authors: Warwick D. , Friedman R. J. , Agnelli G. , Gil-Garay E. , Johnson K. , FitzGerald G. , Turibio F. M.
Published: July 2007

Patients who have undergone total hip or knee replacement (THR and TKR, respectively) are at high risk of venous thromboembolism. We aimed to determine the time courses of both the incidence of venous thromboembolism and effective prophylaxis. Patients with elective primary THR and TKR were enrolled in the multi-national Global Orthopaedic Registry. Data on the incidence of venous thromboembolism and prophylaxis were collected from 6639 THR and 8326 TKR patients.

The cumulative incidence of venous thromboembolism within three months of surgery was 1.7% in the THR and 2.3% in the TKR patients. The mean times to venous thromboembolism were 21.5 days (sd 22.5) for THR, and 9.7 days (sd 14.1) for TKR. It occurred after the median time to discharge in 75% of the THR and 57% of the TKA patients who developed venous thromboembolism. Of those who received recommended forms of prophylaxis, approximately one-quarter (26% of THR and 27% of TKR patients) were not receiving it seven days after surgery, the minimum duration recommended at the time of the study.

The risk of venous thromboembolism extends beyond the usual period of hospitalisation, while the duration of prophylaxis is often shorter than this. Practices should be re-assessed to ensure that patients receive appropriate durations of prophylaxis.
Complete division of the radial nerve associated with a closed fracture of the humeral shaft in a child
Authors: Ogawa B. K. , Kay R. M. , Choi P. D. , Stevanovic M. V.
Published: July 2007

The management of closed fractures of the humerus with an associated nerve palsy remains controversial. With very little written about this injury in children, we present the case of a three-year-old child with a closed humeral shaft fracture in whom surgical exploration and reconstruction of the radial nerve with a sural nerve graft was performed three months after injury. The child regained full function. To the best of our knowledge, this is the first such case to be reported in the English literature.
Assessment and management of chronic patellofemoral instability
Authors: Mulford J. S. , Wakeley C. J. , Eldridge J. D. J.
Published: July 2007

Chronic patellofemoral instability can be a disabling condition. Management of patients with this condition has improved owing to our increased knowledge of the functional anatomy of the patellofemoral joint. Accurate assessment of the underlying pathology in the unstable joint enables the formulation of appropriate treatment. The surgical technique employed in patients for whom non-operative management has failed should address the diagnosed abnormality. We have reviewed the literature on the stabilising features of the patellofemoral joint, the recommended investigations and the appropriate forms of treatment.
The OrthoChina project
Authors: Zhen-Sheng M. , Hong-Ju Z. , Tao Y. , Gang R. , Guo-Sheng D. , Yong-Hua W.
Published: July 2007

Online case discussion may be used for the education of orthopaedic surgeons. The authors developed a website for discussing orthopaedic cases nine years ago and describe its management. It currently has 20 000 registered users.
Advantages and disadvantages of using parallel texts in typological investigations
Authors: Wälchli Bernhard
Published: July 2007

In this paper, advantages and disadvantages of using parallel texts in typological studies are considered according to the criteria of diversity, domains, analysis, per-spective, quality, representativity, and comparability. It is shown in a case study of multi-verb constructions (including serial verb constructions, converb constructions, etc.) in two motion event domains (BRING and RUN) how typology can profit from parallel texts especially in the investigation of quantitative variables. A method is introduced to transform features with continuous distributions into ternary features with low, intermediate, and high values which can then be tested for correlations.
Some remarks on the use of Bible translations as parallel texts in linguistic research
Authors: de Vries Lourens
Published: July 2007

The use of the Bible in parallel text corpora poses special challenges for researchers. The purpose of this paper is to describe the specific nature of Bible translations that sets them apart from other parallel texts such as translations ofHarry Potteror the U.N. Universal Declaration of Human Rights. The special nature of translated Bibles is caused by textual multiplicity, canonical multiplicity and multiplicity of translation types. These three factors reflect one underlying cause, the specific skopos of Bibles: the religious functions of translated Bibles for a wide range of different Jewish and Christian communities.
Parallel texts: using translational equivalents in linguistic typology
Authors: Cysouw Michael , Wälchli Bernhard
Published: July 2007

Parallel texts are texts in different languages that can be considered translational equivalent. We introduce the notion ‘massively parallel text’ for such texts that have translations into very many languages. In this introduction we discuss some massively parallel texts that might be used for the investigation of linguistic diversity. Further, a short summary of the articles in this issue is provided, finishing with a prospect on where the investigation of parallel texts might lead us.
Ghost Nets in the Columbia River: Methods for Locating and Removing Derelict Gill Nets in a Large River and an Assessment of Impact to White Sturgeon
Authors: Kappenman Kevin M. , Parker Blaine L.
Published: July 2007

Lost gill nets, known as ghost nets, represent a threat to aquatic species. Gill nets have been in use in the Columbia River commercial fishery since the mid-1800s, and a number of gill nets continue to be lost each year. We designed a study to investigate the effect of lost nets in the Columbia River. For this study, we developed methods to recover nets and evaluated the use of side-scan sonar (SSS) to locate nets. Grappling in known commercial fishing areas effectively removed nets and was more efficient than relying on SSS to direct recovery efforts. In 154 grapple tows, we recovered 33 nets containing 126 white sturgeon Acipenser transmontanus. Newly lost nets caught significantly more white sturgeon than older nets. Recovered nets at large less than 1 year were responsible for 63% of the total catch, nets at large 1–4 years captured 24%, and nets at large more than 4 years captured 13%. We determined that approximately 10 nets are lost each year, estimated that lost nets have a life span of approximately 7 years, and estimated that ghost nets may kill more than 545 white sturgeon annually. White sturgeon managers may wish to consider developing an outreach program directed at reducing net loss and a net removal program.
Species Distinction and the Biodiversity Crisis in Lake Victoria
Authors: Witte F. , Wanink J. H. , Kishe‐Machumu M.
Published: July 2007

Until the 1970s, the fish fauna of Lake Victoria in East Africa was dominated by about 500 endemic haplochromine cichlid species, which comprised about 80% of the demersal fish mass. The cichlids were extremely diverse ecologically; however, the small diversity in gross morphology and the presence of intraspecific variation made it difficult to distinguish among species. In the first half of the 1980s, the Nile perchLates niloticus, an introduced predator, suddenly boomed and cichlids declined dramatically. During the same period eutrophication increased strongly. With the decline of Nile perch catches in the 1990s, the cichlids showed some recovery. These events have triggered many studies and debates. Disagreements about the severity and causes of the decline often stemmed from considering the cichlid flock as a single unit owing to the lack of proper taxonomic and ecological knowledge. By studying cichlid communities, trophic groups, and individual species, researchers uncovered differential impacts that helped them to unravel the causes of the changes. It seems that lakewide Nile perch predation and eutrophication had the strongest impact and that the fishery only had a local effect. Knowledge of the differential decline and recovery of the haplochromine cichlids and the underlying causes is important for the proper management of biodiversity and the fishery in Lake Victoria. Consequently, knowledge of the systematics of cichlids is a key issue in managing the lake.
Taxonomy: A Precursor to Understanding Ecological Interactions among Schistosomes, Snail Hosts, and Snail‐Eating Fishes
Authors: Stauffer Jay Richard , Madsen Henry , Konings Adrianus , Bloch Paul , Ferreri Cecilia Paola , Likongwe Jeremy , McKaye Kenneth R. , Black Kristin E.
Published: July 2007

We have observed a dramatic decrease in the abundance of snail‐eating fishes and an increase in the prevalence of schistosomiasis among village residents and expatriate tourists at Lake Malawi, Africa, over the past two decades. We hypothesized that these observations were linked by a cause‐and‐effect relationship and that the observed decrease in fish molluscivores permitted an increase in the abundance of snails that are intermediate hosts to schistosomes; we proposed a sampling protocol to determine these relationships. Initially, we thought that intensive study of the interactions among fish, intermediate‐host snails, and human schistosomes in southern Lake Malawi could be applied to other areas throughout the lake. More than two‐thirds of the cichlid species in Lake Malawi are undescribed, the taxonomy of the Bulinus snails is poorly known, and not all strains of Schistosoma hematobium have been identified. Before we can identify the interactions among these components of the system and effectively manage snail‐eating fishes, we must be able to accurately delimit the taxonomic units (e.g., species, populations, and demes) within each of the above groups.
Validity of Self‐Reported Measures for Surveillance of Periodontal Disease in Two Western New York Population‐Based Studies
Authors: Genco Robert J. , Falkner Karen L. , Grossi Sara , Dunford Robert , Trevisan Maurizio
Published: July 2007

Background: Public health and other population‐based studies often depend on participants' self‐reported disease status to assess prevalence, incidence, and disease trends. We sought to assess the feasibility of self‐reported periodontal disease measures using dental history questions combined with demographic and medical history to predict periodontal disease.

Methods: We evaluated results from two separate population‐based studies carried out at the University at Buffalo, Buffalo, New York, i.e., the “Periodontal Infection and Risk for Myocardial Infarction Study,” a study of 1,578 adults assessing the association between periodontal disease and myocardial infarction and the “Periodontal Disease Research Center” (the Erie County Study), an epidemiologic risk assessment study of 1,438 adults. In each study, an extensive list of oral health questions was asked, and a comprehensive medical history, blood analysis using chemistry and hematology tests, and demographic data were collected.

Results: Using a predefined measure of severity of periodontal disease, we compared patients with severe disease to all others (i.e., those with moderate and no or mild disease). We examined areas under the curve (AUC) of the receiver operating curve to determine the best models, adding one, two, or three dental variables in all possible combinations. The AUC maximized at 0.76, and the combined sensitivity and specificity maximized at 142 and were comparable in both studies.

Conclusions: Self‐reported measures of periodontal disease are moderately predictive of clinical attachment loss. The demographic variables of age, race, smoking, gender, and diabetes mellitus accounted for much of the predictive power for self‐reported periodontal disease; however, increases in sensitivity and specificity in the C statistics occurred when questions, including “Gum surgery in the past?,” “Sore gums in the past?,” “Scaling in the past?,” “Bleeding gums now?,” “Periodontal surgery in the past 2 years?,” and “Chewing satisfaction?,” were added to the model.
CDC Periodontal Disease Surveillance Project: Background, Objectives, and Progress Report
Authors: Eke Paul I. , Genco Robert J.
Published: July 2007

This supplement contains papers presented at the 2006 International Association of Dental Research (IADR) symposium entitled “Development of Self‐Reported Measures for Population‐Based Surveillance of Periodontitis.” These papers highlight activities of an independent periodontal disease surveillance workgroup convened by the Division of Oral Health (DOH), Centers for Disease Control and Prevention (CDC), in collaboration with the American Academy of Periodontology, to examine the feasibility of using self‐reported measures for population‐based surveillance of periodontal disease in the United States. This workgroup was convened in 2003 as part of a CDC periodontal disease surveillance project.
The Post-petroleum Future of Academic Libraries
Authors: Hecker Thomas E.
Published: July 2007

Most visions of the future of academic libraries are based on the cornucopian model, that economic growth and technical innovation will continue unabated. An assessment of the future based on the ecological model, taking into account oil depletion, reveals that economic contraction and the abandonment of unsupportable technologies is the more likely scenario. The role of academic libraries may change drastically in the coming decades.
Über eine Klasse infinitesimaler, periodischer Bahnen um die Dreieckslibrationspunkte im problème restreint
Authors: Pedersen P.
Published: July 2007

Die periodischen Bahnen um die Dreieckspunkte im restringierten Dreikörperproblem werden untersucht, indem vorausgesetzt wird, daß die Umlaufszeit in der langperiodischen Librationsellipse sehr nahe die doppelte Umlaufszeit in der kurzperiodischen Librationsellipse ist. Es wird gezeigt, daß die langperiodischen Bahnen dann eine in sich geschlossene Klasse infinitesimaler periodischer Bahnen bilden werden mit einer infinitesimalen äußeren Grenzbahn, die gleichzeitig eine langperiodische Bahn (mit zwei Umläufen) und eine kurzperiodische Bahn (mit einem Umlauf) ist. Wenn die Umlaufszeit in der langperiodischen Librationsellipse genau das doppelte der Umlaufszeit in der kurzperiodischen Librationsellipse ausmacht, wird die äußere Grenzbahn der Bahnklassen auf den Librationspunkt reduziert sein, und die langperiodischen Bahnen um den Librationspunkt herum werden in diesem Falle nicht existieren.