bluuebunny/crossref_metadata_2025 huggingface dataset:
Graft-transmissible induction of potato tuberization by the microRNA miR172
Authors: Martin Antoine , Adam Hélène , Díaz-Mendoza Mercedes , Żurczak Marek , González-Schain Nahuel D. , Suárez-López Paula
Published: August 2009

The photoreceptor phytochrome B (PHYB) and the homeodomain protein BEL5 are involved in the response of potato tuber induction to the photoperiod. However, whether they act in the same tuberization pathway is unknown. Here we show the effect of a microRNA, miR172, on this developmental event. miR172 levels are higher under tuber-inducing short days than under non-inductive long days and are upregulated in stolons at the onset of tuberization. Overexpression of this microRNA in potato promotes flowering,accelerates tuberization under moderately inductive photoperiods and triggers tuber formation under long days. In plants with a reduced abundance of PHYB,which tuberize under long days, both BEL5 mRNA and miR172levels are reduced in leaves and increased in stolons. This, together with the presence of miR172 in vascular bundles and the graft transmissibility of its effect on tuberization, indicates that either miR172 might be mobile or it regulates long-distance signals to induce tuberization. Consistent with this, plants overexpressing miR172 show increased levels of BEL5 mRNA, which has been reported to be transmissible through grafts. Furthermore, we identify an APETALA2-like mRNA containing a miR172 binding site, which is downregulated in plants overexpressing miR172 and plants in which PHYB is silenced. Altogether, our results suggest that miR172 probably acts downstream of the tuberization repressor PHYB and upstream of the tuberization promoter BEL5 and allow us to propose a model for the control of tuberization by PHYB, miR172 and BEL5.
hnRNP I is required to generate the Ca2+ signal that causes egg activation in zebrafish
Authors: Mei Wenyan , Lee Karen W. , Marlow Florence L. , Miller Andrew L. , Mullins Mary C.
Published: August 2009

Egg activation is an important cellular event required to prevent polyspermy and initiate development of the zygote. Egg activation in all animals examined is elicited by a rise in free Ca2+ in the egg cytosol at fertilization. This Ca2+ rise is crucial for all subsequent egg activation steps, such as cortical granule exocytosis, which modifies the vitelline membrane to prevent polyspermy. The cytosolic Ca2+ rise is primarily initiated by inositol 1,4,5-trisphosphate(IP3)-mediated Ca2+ release from the endoplasmic reticulum. The genes involved in regulating the IP3-mediated Ca2+ release during egg activation remain largely unknown. Here we report on a zebrafish maternal-effect mutant, brom bones, which is defective in the cytosolic Ca2+ rise and subsequent egg activation events, including cortical granule exocytosis and cytoplasmic segregation. We show that the egg activation defects in brom bones can be rescued by providing Ca2+ or the Ca2+-release messenger IP3, suggesting that brom bones is a regulator of IP3-mediated Ca2+ release at fertilization. Interestingly, brom bones mutant embryos also display defects in dorsoventral axis formation accompanied by a disorganized cortical microtubule network, which is known to be crucial for dorsal axis formation. We provide evidence that the impaired microtubule organization is associated with non-exocytosed cortical granules from the earlier egg activation defect. Positional cloning of the brom bones gene reveals that a premature stop codon in the gene encoding hnRNP I (referred to here as hnrnp I)underlies the abnormalities. Our studies therefore reveal an important new role of hnrnp I in regulating the fundamental process of IP3-mediated Ca2+ release at egg activation.
Changing from conveyor to work-cell-based systems to deal with fluctuations in demand
Authors: Shishir B N
Published: August 2009

As consumption patterns become increasingly sophisticated and manufacturers strive to improve their competitiveness, not only by offering higher quality at competitive costs, but also by providing a broader mix of products and keeping the range attractive by launching successive new products, turbulence in the markets has intensified. This has driven leading manufacturers to research the development of alternative production systems that are supposed to enable them to operate more responsively. This paper discusses the trend of abandoning the strategy of relying on factory automation technologies and conveyor-based assembly lines, and shifting towards more human-centred production systems based on autonomous work-cells. This paper starts with a theoretical review, linking the need to cope with today's market turbulence with the issue of nurturing more agile organizations. A general view of the diffusion trend of work-cell-based assembly systems in various industries is then presented.
Investigation of the role of dislocation motion in the generation of acoustic emission from metal cutting
Authors: Araújo A J M M , Wilcox S J , Reuben R L
Published: August 2009

Due to the very high strain rates and temperatures encountered in metal cutting, opposing viscous damping forces are the dominant mechanism governing dislocation movement, which is the main mechanism for plastic deformation in metals. However, although viscous damping governs the physics of metal deformation, it is concluded that the detected high frequency acoustic emission (AE) signals arising from metal cutting can only be generated owing to the interaction between moving dislocations and obstacles. This would appear to be the reason why the amplitude of the AE signal cannot be directly related to the cutting power, since it arises from a different generation mechanism. As a result, a qualitative model relating the AE to basic deformation parameters was derived, in which the power of the AE is expected to increase with strain and strain rate, but to decrease with temperature. In addition, the frequency content of the AE is expected to increase with strain rate, to decrease with temperature, and to remain unchanged with strain. These results were validated against data from experimental cutting tests and seem to suggest that the generation of the AE during metal cutting is very heavily dependent on dislocation motion.
Experimentally validated finite element model of the rubbing and ploughing phases in scratch tests
Authors: Doman D A , Bauer R , Warkentin A
Published: August 2009

During single-grain grinding material is removed in three phases, namely the rubbing, ploughing and chip formation phases. The rubbing and ploughing phases are important phases to be considered as they are precursors to chip formation, where material is first removed, and represent process inefficiencies. Investigation of these phases is considerably difficult given the irregular shape of the abrasive grains and as a result these phases are often simulated by scratch tests using spherical indenters. The current work presents a finite element (FE) model of the rubbing and ploughing phases in single-grain grinding. Significant emphasis is placed on the experimental validation of the model, with a view towards its future use as an investigative tool. Single-grain grinding was simulated via a scratch test setup which produced similar surface features and the measured forces were compared against the FE predicted results with good agreement. The model developed here represents an incremental advancement of grinding FE models of the rubbing and ploughing phases by using advanced constitutive models as well as simulating the formation of a scratch.
Analytical and numerical study of the effect of the parting line position and shape in the forging process of parts with different shapes
Authors: Fatemi A , Biglari F R , Alizadeh Noghabi M , Mollaei Dariani B
Published: August 2009

The position and shape of the parting line in forging dies have important effects on parameters such as forging force and energy, material flow, and amount of required material. An investigation was made of the effects of parting-line position on eight types of forged part classified into three main part shapes: axisymmetric parts with an element on one side, axisymmetric parts with elements on both sides, and long parts. For each part, maximum force and energy, material flow, and required material were calculated in different parting-line positions using the finite element method and analytical relationships, and results were compared. For long parts, in addition to different positions, different shapes of the parting line were also considered. In order to evaluate finite element and analytical results, experimental tests were performed on an axisymmetric part in three different parting-line positions. Good agreement among the three types of investigation was obtained.
Fixture control by hydraulic actuation using a reduced workpiece model
Authors: Bakker O J , Popov A A , Ratchev S M
Published: August 2009

In this paper the dynamic behaviour of a part and an actuated fixture system is studied. The part is modelled using the finite element method. Subsequently, a reduced model is established using the Craig—Bampton reduction method in order to create a small-sized model, accurately describing the dynamic behaviour of the part. The clampers and locators of the fixture are modelled as springs. The fixture frame is considered to be much stiffer than the locators such that it provides the zero displacement boundary conditions to the locators. A hydraulic actuator is utilized to provide the adaptive clamping forces. A methodology is presented to obtain the reduced model of the part and to couple it with the model of the active fixture. After investigating proportional control, lag, and lead filters for dynamic compensation, the analysis shows that position feedback can be used effectively to minimize unnecessary displacement of the workpiece.
Generic production planning model for remanufacturing systems
Authors: Doh H-H , Lee D-H
Published: August 2009

Remanufacturing, one of the most advanced product recovery options, processes used or end-of-life products with disassembly, reprocessing, and reassembly operations in such a way that their qualities are as good as new. This paper focuses on production planning in remanufacturing systems over a given planning horizon with discrete time periods. The main decisions are: (a) the number of used or end-of-life products to be disassembled and disposed; (b) the number of parts or components to be reprocessed, disposed, and newly purchased; and (c) the number of products to be reassembled. The objective is to maximize the total profit, i.e. the difference between the sales revenue and the relevant costs. In particular, set-up costs and times are explicitly considered since set-ups are significant in remanufacturing systems. As an extension of the existing literatures on production planning in remanufacturing systems, a generic mixed integer programming model is suggested that incorporates the detailed processes of the remanufacturing process. Then, owing to the complexity of the problem, two types of heuristics based on the linear programming technique are developed. To show the performances of the heuristics, computational experiments were done on some test instances, and the results are reported.
Parametric appraisal of fused deposition modelling process using the grey Taguchi method
Authors: Sood A K , Ohdar R K , Mahapatra S S
Published: August 2009

Dimensional accuracy of a fused deposition modelling (FDM) built part is greatly influenced by many process parameters. In this study, the effect of five process parameters such as layer thickness, part build orientation, raster angle, air gap, and raster width along with their interactions has been studied using Taguchi's L27 orthogonal array. Experimental results indicate that the measured dimension is always more than the desired value along the thickness direction but the length, width, and diameter of hole of test part are less than the desired value. It has been observed that optimal factor settings for each performance characteristic such as percentage change in length, width, thickness, and diameter are different. In order to minimize four responses simultaneously, the grey-Taguchi method is adopted and optimum factor levels have been reported. Finally, overall dimensional accuracy is predicted using artificial neural network (ANN).
Hot die forging process optimization of superalloy IN718 turbine disc using processing map and finite element method
Authors: Zhang H Y , Zhang S H , Li Z X , Cheng M
Published: August 2009

The deformation constitutive equation and the microstructure models in terms of critical strain, dynamic recrystallization, and grain growth for superalloy IN718 have been established based on the isothermal compression tests. Non-isothermal upsetting experiments have been carried out to refine and validate the microstructure evolution models. A processing map has been generated using the flow stress data obtained from the isothermal compression tests. According to the processing map, the optimum hot working parameters for superalloy IN718 have been obtained. The effect of process parameters on the microstructure development during the hot die forging of IN718 turbine disc have been investigated through coupling the microstructure evolution prediction system developed with a commercial FE software, MSC. Superform. To design the hot die forging of IN718 turbine disc, a uniform function of microstructure has been proposed as the goal function. On the basis of simulation results, the optimum hot die forging parameters have been obtained.
Effects of blank design on the electromagnetic flanging process
Authors: Chu Y-Y , Lee R S
Published: August 2009

This paper evaluates the possibility of blank design and process design for shell flanging of the mobile phone and examines the variation of electromagnetic parameters in the flanging process. Aluminium alloy AA6061 T6 was used to simulate the electromagnetic forming process. The influence of magnetic force on the deformed workpiece was then studied by a manual iteration method. From comparison of simulation and experiment, it was evident that the deformation of the workpiece in the forming process had a significant effect on the electromagnetic force. Moreover, owing to the insufficient electromagnetic force and excessive fillet, the workpiece with preform had a better flanging result than the workpiece without preform.
Numerical and experimental investigation of the effect of the pressure path on forming metallic bellows
Authors: Bakhshi-Jooybari M , Elyasi M , Gorji A
Published: August 2009

Tubular metal bellows have wide applications in different industries. They are mainly manufactured in the open die hydroforming process, which comprises two stages of bulge and closing (final forming). In this paper, the effect of pressure path on forming bellows in both stages was studied by finite element simulation and experiment. The results obtained from simulation illustrated that the pressure path influences the production of the desired parts, or the occurrence of bursting or wrinkling defects in the products. Experiments were carried out to verify the simulation results. By using the simulation and experimental results a comprehensive forming window for bellows was presented. Based on this forming window, the wrinkling and bursting defects for bulge and closing stages, and the safe zone for producing the desired part were determined. The study also showed that the number of convolutions does not influence the internal pressure and maximum forming load, but affects the forming energy.
Error identification with a spinning mirror for holography system
Authors: Bang H S , Lee S H , Choi W C
Published: August 2009

Optical elements cannot be perfectly placed in an optical measurement system due to various errors, for instance, errors in lens positions, tilting angles, etc. In this study, an algorithm is proposed to identify these installation errors. A spinning mirror is used to produce many different beam paths so that many measurements can be taken. A simulation is conducted, and it is found that the errors are identified within a few iterations. A more accurate measurement is possible if the errors are compensated.
Numerical and experimental study on prediction of thermal history and residual deformation of double-sided fillet welding
Authors: Biswas P , Mahapatra M M , Mandal N R
Published: August 2009

Distortions occur in almost every arc welded joint. The nature of the created distortion depends on several parameters including the welding speed, plate thickness, welding current, voltage, and restraints applied to the job. The distortions and thermal history of a joint can be measured experimentally but the measurement procedure may be costly and time-consuming. In the present work a numerical elasto-plastic thermomechanical model has been developed for predicting the thermal history and resulting angular distortions of submerged arc welded double-sided fillet joints. A moving distributed heat source was used in the finite element modelling of the double-sided fillet welding to create a realistic simulation of the process. The effect of filler metal deposition was taken into account by implementing a birth-and-death process for the elements. The transient temperature distributions were predicted using temperature-dependent material properties. The angular distortion profiles were predicted based on the transient temperature distributions of the fillet welds. The model yielded results that match the experimental values (with a variation of 5–10 per cent for the maximum values of the distortions and a variation of 8 per cent for peak temperatures).
Development of an electro static lubrication system for drilling of SCM 440 steel
Authors: Reddy N S K , Yang M
Published: August 2009

The growing demands for high productivity of machining require the use of high cutting speeds and feed rates. Such machining inherently produces a high cutting temperature, which not only reduces tool life, but also impairs the product quality. Application of cutting fluid influences the performance of machining because of its lubrication and cooling actions but the environmental concerns call for the reduced use of cutting fluids in machining operations. Near-dry machining, such as minimum quantity lubrication, is regarded as one of the solutions to this difficulty. In the current work, cutting fluid was applied as a continuous high-velocity jet at the machining zone, at an extreme low rate using a fluid application system, by electro static lubrication (ESL), during the drilling of SCM 440 (hardened) steel. In the first stage of this work, experiments were carried out to investigate the role of the ESL system on tool wear, hole diameter, thrust force, and surface finish of the product in machining of SCM 440 steel. In the second stage, a comparative performance analysis of the ESL system with minimum quantity of lubricant (MQL) and dry machining was conducted. Results indicate that there is a considerable improvement in the performance of machining SCM 440 steel using the ESL setup when compared with MQL and dry machining in terms of considered parameters.
Comprehensive uncertainty analysis of a Wiebe function-based combustion model for pilot-ignited natural gas engines
Authors: Cho H , Krishnan S R , Luck R , Srinivasan K K
Published: August 2009

This paper presents a comprehensive uncertainty analysis of a Wiebe function-based combustion model for advanced low-pilot-ignited natural gas (ALPING) combustion in a single-cylinder research engine. The sensitivities, uncertainty magnification factors (UMFs), and uncertainty percentage contributions (UPCs) of different experimental input variables and model parameters were investigated. First, the Wiebe function model was validated against experimental heat release/mass burned fraction profiles and cylinder pressure histories for three pilot injection timings (start of injection (SOI)): −20°, −40°, and −60° after top dead center (ATDC). Second, the sensitivities and UMFs of predicted cylinder pressure histories were determined. Finally, crank angle-resolved uncertainties were quantified and mapped as ‘uncertainty bounds’ in predicted pressures, which were compared with measured pressure curves with error bars for cyclic variations. The Wiebe function-based combustion model with a quadratic interpolation equation for the specific heat ratio ( γ) provided reasonable cylinder pressure and heat release/mass burned fraction predictions for all SOIs (better for −20° and −60° ATDC SOIs compared with −40° ATDC). Uncertainty analysis results indicated that γ (parameters in the quadratic interpolation equation), compression ratio, mass and lower heating value of natural gas trapped in the cylinder, overall trapped mass, and ignition delay were important contributors to the overall uncertainty in predicted cylinder pressures. For all SOIs, γ exhibited the highest UPC values (80–90 per cent) and therefore, γ must be determined with the minimum possible uncertainty to ensure satisfactory predictions of cylinder pressure histories. While the importance of γ in single-zone combustion models is well recognized, the specific contribution of the present analysis is quantification of the crank angle-resolved UPCs of γ and other model parameters to the overall model uncertainty. In this paper, it is shown that uncertainty analysis provides a unique methodology for quantitative validation of crank angle-resolved predictions from any type of engine combustion model with the corresponding experimental results. It is also shown that uncertainties in both predicted and measured cylinder pressures and heat release rates must be considered while validating any engine combustion model.
Semi-active vibration isolation using a near-zero-spring-rate device: steady state analysis of a single-degree-of-freedom model
Authors: Krishna Y , Shrinivasa U
Published: August 2009

A vibration isolator is described which incorporates a near-zero-spring-rate device within its operating range. The device is an assembly of a vertical spring in parallel with two inclined springs. A low spring rate is achieved by combining the equivalent stiffness in the vertical direction of the inclined springs with the stiffness of the vertical central spring. It is shown that there is a relation between the geometry and the stiffness of the individual springs that results in a low spring rate. Computer simulation studies of a single-degree-of-freedom model for harmonic base input show that the performance of the proposed scheme is superior to that of the passive schemes with linear springs and skyhook damping configuration. The response curves show that, for small to large amplitudes of base disturbance, the system goes into resonance at low frequencies of excitation. Thus, it is possible to achieve very good isolation over a wide low-frequency band. Also, the damper force requirements for the proposed scheme are much lower than for the damper force of a skyhook configuration or a conventional linear spring with a semi-active damper.
A new passive non-linear damper for automobiles
Authors: Kalyan Raj A H , Padmanabhan C
Published: August 2009

Passive linear suspension systems are limited in their ability to improve ride characteristics owing to the conflicting interdependence between ride comfort, road holding, and space occupied by the suspension system. Non-linear systems can improve the performance of passive designs by de-linking the various metrics involved in ride comfort. Based on the control strategies used in semi-active suspensions, a new non-linear damper design is proposed, where the damping rapidly changes with stroke. This design has been fabricated and tested to validate the analytical expressions governing the damping as a function of stroke. Experimental results show excellent agreement with analytical expressions. The novel damper model has been used along with an existing non-linear spring design, in a quarter-car simulation. The results indicate that the non-linear design leads to significantly lower acceleration levels when compared with a linear system, without any compromise on other metrics.
Finite element analysis of the effect of up-armouring on the off-road braking and sharp-turn performance of a high-mobility multi-purpose wheeled vehicle
Authors: Grujicic M , Bell W C , Arakere G , Haque I
Published: August 2009

A comprehensive finite element investigation is carried out of the effect of up-armouring on the off-road performance of a prototypical high-mobility multi-purpose wheeled vehicle. The effect of up-armouring on the vehicle performance was investigated under the following off-road manoeuvres: straight-line flat-land braking; straight-line off-angle downhill braking; sharp left turn. In each case, the appropriate vehicle performance criteria are identified and the parameters used to quantify these criteria are defined and assessed. The computational results obtained clearly revealed the compromises in vehicle off-road performance caused by the up-armouring employed to improve vehicle blast and ballistic protection performance and survivability. The results obtained are also analysed and explained in terms of general field-test observations in order to judge the physical soundness and fidelity of the present computational approach. Finally, the potential benefits and ramifications of lightweight up-armouring in providing the needed level of blast and/or ballistic performance while causing fewer compromises in the vehicle off-road performance are also discussed.
Effects of transient diesel engine operation on its cyclic heat transfer: an experimental assessment
Authors: Rakopoulos C D , Mavropoulos G C
Published: August 2009

This paper presents results from the analysis of experimental data with the aim of investigating the cyclic, instantaneous heat transfer phenomena occurring in both the cylinder head and exhaust manifold wall surfaces of a direct injection, air-cooled diesel engine, operating under transient events (long-term), viz. during a sudden change in engine speed and/or load, rather than the usual steady state. The experimental installation allowed both for long- and short-term signal types to be recorded on a common time reference base during the transient event. Processing of experimental data was accomplished using a modified version of one-dimensional heat conduction theory with Fourier analysis, capable of catering for the special characteristics of transient engine operation. Based on this model, the evolution of local surface heat flux during a transient event was calculated. Two engine transient events are examined, which present a key difference in the way the load and speed changes are imposed on each one of them. It is revealed that in the case of a ‘ramp’ transient the amplitude of wall surface temperature and heat flux variation in the combustion chamber during the first 20 engine cycles was increased by almost three times more than the corresponding ones during steady state operation. At the same time, temporal gradients of cylinder pressure and wall surface temperature are also sharply increased in the combustion chamber and exhaust manifold surfaces. The variation of cylinder pressure, surface temperature, and heat flux is altered significantly during the transient event, with their peak values either advanced or retarded compared with those for the corresponding steady state operation. The previous observations are moderated or even vanished in the case of a ‘slow pace’ transient variation, revealing the significant influence of engine speed and load triggered by the external command, on the response of heat transfer variables. During a ramp transient, the amplitude of wall temperature swing is increased significantly even at a depth of a few millimetres below the surface of the combustion chamber, thereby influencing the dissipation of heat towards its external layers. Under these circumstances, the depth of penetration for temperature oscillations inside the metal volume is also significantly increased.
In-vivo kinematics of knee prostheses patients during level walking compared with the ISO force-controlled simulator standard
Authors: Ngai V , Schwenke T , Wimmer M A
Published: August 2009

Differences between wear-scar features of simulator-tested and retrieved tibial total knee replacement (TKR) liners have been reported. This disagreement may result from differences between in-vivo kinematic profiles and those defined by the standard. The purpose of this study was to determine the knee kinematics of a TKR subject group during level walking and to compare them with the motion profiles produced by a wear test conducted according to the force-controlled knee wear testing ISO 14243-1 standard. Ten patients with a posterior cruciate ligament-retaining TKR design were gait tested using the point cluster technique to obtain flexion—extension (FE) rotation, anterior—posterior (AP) translation, and internal—external (IE) rotation motions during a complete cycle of level walking. Motion data were directly compared with the output kinematics from the wear test. The subjects exhibited an FE rotation pattern similar to the output from ISO-14243-1; however, they had higher midstance knee flexion angles. For both AP translation and IE rotation, the standard profiles had significantly smaller total ranges of motion than seen in vivo, with noticeably different patterns of motions. For this particular implant design, significant differences were found in both the pattern and the magnitudes of in-vivo motion during level walking compared with the ISO-14243-1 standard.
Experimental characterization and damage identification of polymeric film constituting stratospheric super pressurized balloons
Authors: Chaabane M , Dalverny O , Mistou S , Alexis J , Deramecourt A
Published: August 2009

Super-pressure balloons developed by the Centre National d'Etudes Spatiales (CNES) provide a cheap, non-polluting, and quickly operable platform for in-situ measurements at altitudes of up to about 25 km, and for remote sensing of the earth, the atmosphere, and space from regions inaccessible to other means of transport over similar observation periods. They are lifted by a helium-filled, approximately spherical, closed envelope made of a polyethylene terephthalate (PET)-based multi-layer polymeric film. It appears that during working flights, these balloons may sometimes explode prematurely. For this reason, the CNES is carrying out research programme and experiments in order to predict better stability of balloon flight and guarantee a life span corresponding to the technical requirements. In this article, experimental results are presented concerning the identification and characterization of film damage induced by simple and triple wrinkling. The present authors started from microscopic observations of damage involving wrinkles and from unidirectional tensile tests of the damaged film with simple and triple wrinkles. During tensile tests, in order to observe the zone affected by wrinkling, an optical technique was used (electronic speckle pattern interferometry) to measure local strain in the damaged area. The correlation between the strain level in the wrinkles observed during tensile testing and the evolution of damage parameters depending on strain gives the damage parameter in the case of simple and triple wrinkling.
How tight is sphere-packed formation flying?
Authors: Gu D-W , Kim Y , Postlethwaite I
Published: August 2009

In this article, a method for finding a tight formation of unmanned air vehicles (UAVs) via the classical sphere packing scheme is introduced. First, the tight formation finding problem is translated to the problem of maximizing the second smallest eigenvalue λ2( G) of the graph Laplacian L G. It is then shown how close the formation Gs, obtained from the sphere packing scheme, is to the optimal formation G∗ that maximizes λ2( G). λ2( G∗)/λ2( Gs) is shown to be relatively small (close to 1) when the communication strength between two UAVs decays slowly with the distance between the two UAVs. This result is also useful in that Gs can serve as a certificate that allows every graph to be quantitatively compared to G∗. In the light of this tight formation result, a modelling technique is given for the optimal airborne refuelling of multiple UAVs.
Design of linear parameter varying trajectory tracking controllers for an unmanned air vehicle
Authors: Natesan K , Gu D-W , Postlethwaite I
Published: August 2009

This article presents a trajectory tracking controller design approach for an unmanned air vehicle using the linear parameter varying (LPV) methods. The longitudinal and lateral controllers are designed using an inner-outer loop structure with the inner loop LPV controller designed first using μ-synthesis. The inner loop is then approximated with a reference model and the outer loop is designed using loop-shaping techniques. Flight trajectory is expressed in terms of earth co-ordinates, which the outer loop controller converts into reference signals for the inner loop. Full-scale non-linear simulations are used to test the efficiency of the designed controller and of the proposed design approach.
Correction of the definition of mass flow parameter in dynamic inflow modelling
Authors: Murakami Y , Houston S S
Published: August 2009

The dynamic inflow model, which has been extensively developed by Peters and his co-workers for the last two decades, is a powerful tool for predicting the induced velocity distribution over a rotor disc. Scant attention has, however, been paid so far in using the model to analyse an autorotative rotor. The authors identified a necessary change to the mass flow parameter of the original model of Peters for autorotating rotors. In response, questions were raised by readers about how the modified and original inflow parameters should consistently be explained, why the original model of Peters is insufficient for autorotation, and how the validity of the modified mass flow parameter can mathematically be enunciated. Indeed, the discussion in the article by Murakami and Houston (2008) was held in a manner that readers might have received an impression that the modified model was derived independently of the original model, and the connection to the original model was not clearly presented. This technical note is written with an aim to elucidate the mathematically consistent relationship between the original and modified mass flow parameters, and it is confirmed that the original definition of the mass flow parameter contains an error in its definition. It is concluded that the unified mass flow parameter, which is presented in this article, should always be used in the dynamic inflow model.
Autonomous guidance for intelligent missiles based on chaotic perception—action dynamics
Authors: Yu X-L , Sun Y , Liu J , Xiang W
Published: August 2009

In this article a new reactive mechanism based on perception—action dynamics for multi-sensory integration applied to an intelligent missile guidance system is proposed. The strategy is inspired by the olfactory bulb neural activity observed in rabbits subject to external stimuli. The new missile guidance technique exploits the use of a multiscroll chaotic system which is able to be controlled in real-time towards less complex orbits, such as periodic orbits or equilibrium points, considered as perceptive orbits. These are subject to real-time modifications on the basis of environmental changes acquired through a synthetic aperture radar sensory system. The mathematical details of the approach are given including simulation results in a virtual environment. The results demonstrate the capability of autonomous guidance for missile in complex spatial environments.
Characterization, quantification, and replication of human sinus bone for surgery simulation phantoms
Authors: Radley G J , Sama A , Watson J , Harris R A
Published: August 2009

The requirement for artificial but realistic, tactile, anatomical models for surgical practice in medical simulation is increasingly evident and shows potential for greater efficiency and availability, and lower costs. Anatomically correct, detailed models with the physical surgical characteristics of real tissue, combined with the ability to reproduce one-off cases, would provide an invaluable tool in the development of surgery. This research work investigates the capture of geometrical and physical data from the human sinus to subsequently direct the production and optimization of such simulation phantoms. Micro-computed tomography analysis of the entire sinus was performed to characterize the sinus complex geometry. Following an extensive review, specialized mechanical testing apparatus and methods relevant to the surgical methods employed were designed and produced. This provided comparative analysis methods for both biological and artificial phantom materials and allowed the optimization of phantom materials with respect to the derived target values.
Muscle-driven forward dynamics simulation for the study of differences in muscle function during stair ascent and descent
Authors: Ghafari A Selk , Meghdari A , Vossoughi G R
Published: August 2009

The main scope of this study is to analyse muscle-driven forward dynamics simulation of stair locomotion to understand the functional differences of individual muscles during the movement. A static optimization was employed to minimize a performance criterion based on the muscle energy consumption to resolve muscle redundancy during forward dynamics simulation. The proposed method was employed to simulate a musculoskeletal system with ten degrees of freedom in the sagittal plane and containing 18 Hill-type musculotendon actuators per leg. Simulation results illustrated that simulated joint kinematics closely tracked experimental quantities with root-mean-squared errors less than 1°. In addition, estimated muscle activations have a good agreement with the salient features of the electromyographic recordings of the major muscles of the lower extremity. Distribution of mechanical power for individual muscles was estimated to elucidate the muscle's contribution to body support and forward progression during stair locomotion. The accuracy and relatively high computational performance of the proposed method make it suitable to generate subject-specific simulations of various activities for individuals with movement disorders in clinical studies.
Three-dimensional ultrasound imaging
Authors: Prager R W , Ijaz U Z , Gee A H , Treece G M
Published: August 2009

This review is about the development of three-dimensional (3D) ultrasonic medical imaging, how it works, and where its future lies. It assumes knowledge of two-dimensional (2D) ultrasound, which is covered elsewhere in this issue. The three main ways in which 3D ultrasound may be acquired are described: the mechanically swept 3D probe, the 2D transducer array that can acquire intrinsically 3D data, and the freehand 3D ultrasound. This provides an appreciation of the constraints implicit in each of these approaches together with their strengths and weaknesses. Then some of the techniques that are used for processing the 3D data and the way this can lead to information of clinical value are discussed. A table is provided to show the range of clinical applications reported in the literature. Finally, the discussion relating to the technology and its clinical applications to explain why 3D ultrasound has been relatively slow to be adopted in routine clinics is drawn together and the issues that will govern its development in the future explored.
A review of medical robotics for minimally invasive soft tissue surgery
Authors: Dogangil G , Davies B L , Rodriguez y Baena F
Published: August 2009

This paper provides an overview of recent trends and developments in medical robotics for minimally invasive soft tissue surgery, with a view to highlight some of the issues posed and solutions proposed in the literature. The paper includes a thorough review of the literature, which focuses on soft tissue surgical robots developed and published in the last five years (between 2004 and 2008) in indexed journals and conference proceedings. Only surgical systems were considered; imaging and diagnostic devices were excluded from the review. The systems included in this paper are classified according to the following surgical specialties: neurosurgery; eye surgery and ear, nose, and throat (ENT); general, thoracic, and cardiac surgery; gastrointestinal and colorectal surgery; and urologic surgery. The systems are also cross-classified according to their engineering design and robotics technology, which is included in tabular form at the end of the paper. The review concludes with an overview of the field, along with some statistical considerations about the size, geographical spread, and impact of medical robotics for soft tissue surgery today.
A two-degree-of-freedom hip exoskeleton device for an immature animal model of exercise-induced Legg—Calvé—Perthes disease
Authors: Zhang J-F , Yang C-J , Wu T , Li J-H , Xu Z-S , Chen Y
Published: August 2009

Legg—Calvé—Perthes disease (LCPD) is a significant problem in healthcare because it so commonly affects young adults and immature athletes, primarily gymnasts. In this paper, a two-degree-of-freedom (2-DOF) hip exoskeleton device was developed for study on an immature animal model of exercise-induced LCPD. The exoskeleton device can reproduce the repetitive actions and forceful centrality impingements on the coxafemoral head that occur in sports such as gymnastics and acrobatics. It initiated a new method rather than the traditional medical or physiological operation method to establish an animal model of LCPD and allowed for the development and testing of new treatments. Ten immature New Zealand white rabbits were selected for the experiment. Their right legs were driven to achieve repetitive extension/flexion and abduction/adduction beyond the normal range of motion, with centrality impingements at the maximum flexion position, while their left legs were kept in the initial healthy status and acted as the comparing reference. Four weeks later, the basic symptoms of early LCPD of the femoral head appeared. The results of X-ray, magnetic resonance imaging (MRI), gross anatomy observation, and H-E section also revealed it.
Comparing different data collection and analysis techniques for quantifying healthy knee joint function during stair ascent and descent
Authors: Whatling G M , Evans S L , Holt C A
Published: August 2009

There is currently no standard data collection or analysis method for the assessment of stair gait using motion analysis. This makes the comparison of results from different studies difficult. It is important to gain an appreciation of the discrepancies in kinematic and kinetic information generated by employing different computational approaches, as these differences may be critical in cases where methodologies were to change over a long-term study. This study explores the effect of using different methodologies for the assessment of non-pathological knee function of ten subjects during stair ascent and descent. Two methods of computing knee kinematics were compared: (a) using in-house software and a pointer method of anatomical calibration and (b) using commercial software, Visual3D (C-motion, Inc.) and skin-mounted markers. Significant differences were found between the two methods when calculating a frontal plane range of motion ( p<0.05). Three methods of computing knee moments were compared. Knee moments computed using the inverse dynamic analysis (IDA) approach of Visual3D (C-motion, Inc.) were significantly different ( p<0.05) to those calculated using in-house IDA software that ignores the foot and ankle and to those computed using a vector cross-product approach. This study highlights the implications of comparing data generated from different collection and analysis methods.
The potential of plasma electrolytic oxidized eutectic aluminium-silicon alloy as a cylinder wall surface for lightweight engine blocks
Authors: Mistry K , Priest M , Shrestha S
Published: August 2009

A series of tests was conducted using a reciprocating tribometer to evaluate the tribological performance of a plasma electrolytic oxidation (PEO) treated eutectic aluminium-silicon alloy and was compared with a more conventional nickel-ceramic (Ni-SiC) coating as a reference. The counterpart was a gas-nitrided steel top piston ring and the lubricant was a group III base oil blended with standard detergent and dispersant additives, both with and without dispersions of very fine particles of molybdenum disulphide as a friction modifier. Scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, and stylus profilometry were employed to characterize the morphology, elemental composition, and surface force analysis of the tribofilm and the wear profile. The tribological performance of the PEO transformed surface was found to be similar to the Ni-SiC coating in the short-duration tribometer experiments undertaken with fully flooded lubrication and at low-speed conditions, with potentially greater durability in the longer term given the properties of the transformed surface layer.
Connectivity characterization of three-dimensional surface topography based on mathematical morphology
Authors: Liu X , Liu K , Wang W , Gui C
Published: August 2009

In order to understand the correlation between the connection of surface microstructures and lubrication and seal performances, a novel method to characterize the connectivity of the three-dimensional (3D) surface topography, based on mathematical morphology, is presented. A new concept of surface connectivity index is proposed. Quantitative description of the connectivity of 3D topography in digital space is made by recursive operation of multiscale erosion. The variations of the surface connectivity index with the surface height are approached. The reliability of the surface connectivity measure method is analysed. As a practical application, the connectivity of the 3D topography of a cylinder liner of an engine is evaluated. The results of calculation and analysis indicate that this approach has an explicit signification and reliable arithmetic, and it can effectively describe the connection characteristics of surface structures.
Kinematics of a hyper-redundant manipulator by means of screw theory
Authors: Gallardo-Alvarado J , Rico-Martínez J M
Published: August 2009

In this work the kinematics of a hyper-redundant manipulator built with an optional number of parallel manipulators with identical topologies assembled in series connection is carried out by using the theory of screws. First, closed-form solutions to solve the kinematics, up to the acceleration analysis, of the base module, an asymmetrical three-degree-of-freedom (dof) parallel manipulator with mixed motions, are derived using geometric procedures and the theory of screws; later, the symbolic results thus obtained are applied recursively to solve the kinema-tics of the proposed hyper-redundant manipulator. A 12-dof hyper-redundant manipulator is included as a case study.
Eigenfrequencies of generally restrained Timoshenko beams
Authors: Quintana V , Grossi R
Published: August 2009

This article deals with the free transverse vibration of a Timoshenko beam with intermediate elastic constraints and ends elastically restrained against rotation and translation. A combination of the Ritz method and the Lagrange multiplier method and also the standard Ritz method are used to examine the free vibration characteristics of the mentioned beam. Trial functions denoting the transverse deflections and the normal rotations of the cross-section of the beam are expressed in polynomial forms.

In order to obtain an indication of the accuracy of the developed mathematical models, some cases available in the literature have been considered. New results are presented for different end conditions and intermediate elastic restraints.