bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation into the effect of proteoglycan molecules on the tribological properties of cartilage joint tissues
Authors: Pickard J , Ingham E , Egan J , Fisher J 
Published: October 2002

The aim of this research was to investigate the role of the hydrophilic properties of the proteoglycan molecules within the cartilage matrix, on the tribological properties of joint tissues in the mixed and boundary lubricating regime. Bovine articular cartilage, bovine meniscus and bovine cartilage that had been degraded to remove the chondroitin sulphate from its proteoglycans were studied in order to investigate differences in their friction and compression responses. The tissues were tested on a sliding friction rig under nominal contact stresses of 0.5 and 4 MPa. The compression tests were carried out under a 0.8 MPa contact stress. The compression tests showed the cartilage and meniscus deforming at the same rates, but the degraded cartilage deformed more quickly to reach its equilibrium position in a shorter period of time. The friction tests carried out at a constant load revealed the friction of the meniscus rising more rapidly with loading time than the cartilage. The degraded cartilage followed an almost identical curve as the untreated cartilage. Although the reduced proteoglycan content of the degraded cartilage substantially altered the biphasic compression response, it did not have an effect on the frictional properties of the tissue.
The compressive strength of articular cartilage
Authors: Kerin A J , Wisnom M R , Adams M A 
Published: October 2002

Articular cartilage provides the smooth bearing surfaces in freely moving (synovial) joints. Its mechanical properties are important because structural failure of cartilage is closely associated with joint disorders, including osteoarthritis. Some mechanical properties of cartilage are well characterized, but little is known about its compressive strength. A technique for measuring cartilage compressive strength is evaluated, and an overview of experiments which relate strength to stiffness and tissue hydration is given. Specimens of bovine articular cartilage-on-bone, approximately 15 mm square, were loaded on a hydraulic materials testing machine using flat impermeable indentors. Linear-ramp loading/unloading cycles of 1 s duration, and of increasing severity, were applied until failure was evident on force-displacement graphs. Some specimens were tested following a 30 min period of creep loading. Inkstaining and histology were used to locate the site of initial damage to each specimen. Specimen failure occurred first in the cartilage surface layer at a nominal applied stress of 14–59 MPa (mean 35.7 MPa). Mechanical properties were little affected by specimen or indentor size, provided both remained within defined limits, and compressive strength could be measured to an accuracy of approximately ±5 per cent. Compressive stiffness was a significant predictor of strength, but only if it was measured at high levels of stress. Strength increased following creep-induced water loss, and initial mechanical damage could propagate under moderate cyclic loading. This technique for measuring cartilage compressive strength has potential for investigating the causes of cartilage failure in vivo
Osteotransductive bone cements
Authors: Driessens F C M , Planell J A , Boltong M G , Khairoun I , Ginebra M P 
Published: October 2002

Calcium phosphate bone cements (CPBCs) are osteotransductive, i.e. after implantation in bone they are transformed into new bone tissue. Furthermore, due to the fact that they are mouldable, their osteointegration is immediate. Their chemistry has been established previously. Some CPBCs contain amorphous calcium phosphate (ACP) and set by a sol-gel transition. The others are crystalline and can give as the reaction product dicalcium phosphate dihydrate (DCPD), calcium-deficient hydroxyapatite (CDHA), carbonated apatite (CA) or hydroxyapatite (HA). Mixed-type gypsum-DCPD cements are also described. In vivo rates of osteotransduction vary as follows: gypsum-DCPD > DCPD > CDHA ≍ CA > HA. The osteotransduction of CDHA-type cements may be increased by adding dicalcium phosphate anhydrous (DCP) and/or CaCO3 to the cement powder. CPBCs can be used for healing of bone defects, bone augmentation and bone reconstruction. Incorporation of drugs like antibiotics and bone morphogenetic protein is envisaged. Load-bearing applications are allowed for CDHA-type, CA-type and HA-type CPBCs as they have a higher compressive strength than human trabecular bone (10 MPa).
Applications of computer modelling for the design of orthopaedic, dental and cardiovascular biomaterials
Authors: Vander Sloten J , Hobatho M-C , Verdonck P 
Published: October 2002

Biomaterials do not escape from the general trend present in all contemporary science and technology towards increasing use of computers and information technology. In this paper the use of computer modelling for the design of biomaterials is discussed. The word 'biomaterials' is interpreted in its broadest sense, i.e. referring to any foreign object brought into the body for temporary or permanent use. Computer modelling will first be discussed as a tool to model biological structures (bones, arteries) or to investigate and simulate biological interactions at implant-host interfaces. It will then be illustrated how computer modelling, using insights gained from the modelling of the biological structures themselves, is used in the design process of dental, orthopaedic and cardiovascular prostheses. The area of computer modelling for biomaterials applications has become so vast that an exhaustive overview is impossible in the framework of one paper. Rather, some illustrative case studies will be discussed which are, in the opinion of the authors, representative of general trends in this challenging domain of science on the boundary between engineering and medicine.
Experimental investigations of the externally heated valve engine model
Authors: Brzeski L , Kazimierski Z 
Published: October 2002

The experimental investigations of the first model of the externally heated valve engine carried out during 1998-9 are the subject of this paper. The working gas of the engine is air. A detailed description of the engine equipped with two consecutively working heaters is given. Two kinds of heaters were constructed and investigated. The experimental stand and the measurement system are described. In this first stage of the engine investigation, electric radiators were used as the external source of heat. The main aim of the experimental investigations was focused on measurements of time-dependent pressures inside the expander and compressor cylinders. The pressures were measured by means of two kinds of pressure transducers (piezoresistive and piezoelectric) to get confidence in the obtained results. The conducted investigations prove that The engine model has an operating ability. Comparisons of the experimental and theoretical pressures inside the expander and compressor show a satisfactory agreement. It confirms that the engine operates according to the original thermodynamical cycle and exhibits the internal power and efficiency predicted by the computer simulation. The experiences gained during these investigations have been used to modify the engine model, which is outlined in this paper.
Application of simulated annealing to inverse design of transonic turbomachinery cascades
Authors: Tiow W. T. , Yiu K. F C. , Zangeneh M 
Published: October 2002

In turbomachinery blade design, inverse methods and optimization techniques are often applied independently to produce high performance blade shapes. The idea of using an optimization algorithm to seek the optimal target distribution for an inverse design methodology has been explored. However, these efforts have been made mainly in the design of single aerofoils. In this paper, a new inverse design method is coupled with a simulated annealing algorithm to search for the optimum turbomachinery cascade shape. In order to speed up the algorithm, a database of generated designs is set up and the nearest match is selected to initialize subsequent calculation. The proposed computational procedure equips engineers with an automatic design tool with which the inverse method may be applied in isolation or combined with the optimization algorithm to produce the optimum. The inverse methodology is based on a cell vertex, finite volume time-marching flow solver that gives the viscous cascade flow solution in both the subsonic and the transonic flow regimes. The cascade shape is computed subject to an imposed distribution of the mass-averaged tangential velocity and a specified tangential thickness profile. The solver code is validated using experimental data and the accuracy of the inverse method is verified by regenerating a known cascade geometry starting from a different one using its mass-averaged tangential velocity distribution. In combining the inverse methodology with the optimization algorithm, the mass-averaged tangential velocity distribution is parametrized using a cubic B-spline curve and the proposed simulated annealing algorithm is applied to predict the optimal distribution by minimizing loss. The overall procedure is demonstrated to produce optimum shapes of a transonic axial turbine and an axial compressor rotor.
Worldwide use of biomass in power generation and combined heat and power schemes
Authors: Arbon I. M. 
Published: October 2002

Biomass is a truly renewable, sustainable source of energy; in its firewood form, at least, it has always been humanity's primary fuel. Nevertheless, it is only in the very recent past that it has been regarded as a viable substitute in power generation for the fossil fuels that have caused most of the world's environmental pollution problems. This paper distinguishes between truly renewable, sustainable sources of fuel from agricultural sources, i.e. biomass, and the disposal of domestic, urban and hazardous waste in energy-from-waste (EfW) plants; although these differences may appear to be marginal, and any EfW plant is of value for power generation, there are particular reasons why the generation of power from genuine biomass reaps environmental benefits. The bulk of the paper discusses the generation of electric power from a variety of different biomass substances, some from purpose-grown ‘energy crops’ but mostly from ‘agricultural residues’. While this is predominantly through conventional combustion systems with steam turbines, more recent experience of both gasification and pyrolysis, with power generation by other prime movers, such as gas turbines and reciprocating engines is also covered. The concluding section of the paper looks briefly at the relative benefits of combustion, gasification and pyrolysis and what the future is likely to hold for each of these technologies.
Experimental and numerical investigation on flow and heat transfer in large-scale, turbine cooling, representative, rib-roughened channels
Authors: Arts T , Rau G , Çakan M , Vialonga J , Fernandez D , Tarnowski F , Laroche E 
Published: October 2002

This paper deals with the application of a three-dimensional Navier-Stokes solver for the prediction of steady viscous compressible flow and heat transfer in a square channel with one rib-roughened wall. The computation results are compared with detailed experiments carried out at the von Karman Institute. The two-dimensional computations agree rather well with the experiments for the prediction of the aerodynamics, even if the recirculation length is overestimated. In this case, a k-l turbulence model seems to be sufficient. However, heat transfer between the ribs is poorly matched except when a thermal ASM (algebraic stress model) turbulence model (GGDH, or generalized gradient diffusion hypothesis), which computes the u iθ (velocity-temperature) correlations by algebraic equations, is used. The three-dimensional computations capture the correct position of the reattachment point with the k-l turbulence model. It is nevertheless necessary to use the ASM turbulence model to find vortices turning the correct way in the cross-sections. These are indeed secondary flows of the second kind which are mainly due to turbulence anisotropy when the ribs are inclined at 90° to the flow direction.
United States high-level radioactive waste management programme: Current status and plans
Authors: Richardson J A 
Published: October 2002

Commercial reactor nuclear power generation in the United States is produced by 107 units and, during 1996, represented over 21 per cent of the nation's electricity generation in 34 of the 50 states and, through electric power wheeling, between states in most of the 48 contiguous states. Spent fuel is stored in fuel pools at 70 sites around the country and the projected rate of spent fuel production indicates that the current pool storage will be exceeded in the out years of 2000, 2010 and 2020 at 40, 67 and 69 of these sites respectively. The total accumulation projected by the end of 1996 at reactor sites is 33 700 metric tons of heavy metal (MTHM), with projections for increasing accumulations at annual rates of between 1800 and 2000 to produce an end of life for all commercial nuclear reactors of about 86 000 MTHM. There are presently eight facilities in six states with out-of-pool dry storage amounting to 1010 MTHM and this dry storage demand will increase. Based on all current commercial reactors achieving their 40 year licensed operation lifetimes, the dry storage needs will increase to 3128 MTHM at 28 sites and 20 states by 2000 and 11 307 MTHM at 58 sites in 32 states by 2010; the year 2010 is the present scheduled operation date for the federal mined geological disposal repository being characterized by the USDOE at Yucca Mountain, Nevada. The enabling statute for the federal high-level radioactive waste management programme is the 1982 Nuclear Waste Policy Act (NWPA) which charges the USDOE with the responsibility for the disposal of HLW and spent nuclear fuel. The Act also charges the utilities with the responsibility for managing their spent nuclear fuel until the USDOE can accept it into the federal waste management system. The funding for the federal programme is also stipulated by the Act with the creation of the Nuclear Waste Fund, through which the electric utilities entered into contract with the USDOE by payment of a fee of 1 mill per kilowatt hour sold and for which the USDOE would start collection of spent fuel from the reactor sites starting 31 January 1998.
Advances in laboratory tests for predicting coal-related combustion problems
Authors: Gibbins J R , Williamson J 
Published: October 2002

Problems in pulverized fuel combustion in steam-raising plant that can be attributed to the nature of the coal being fired include excessive slagging and fouling, poor char burnout, NOx emissions and flame stability. Coal performance in these areas can, to some extent, be related to the results from existing coal characterization tests but, particularly for coals from unfamiliar areas, these correlations may be unreliable and misleading. For example, attempts to relate slagging propensity to the chemical composition of the coal ash have met with only limited success. It now seems clear that empirical indices and viscosity measurements do not reflect the complex mineral interactions that occur during combustion. However, new microanalysis techniques, capable of characterizing the distribution of mineral matter in a pulverized fuel (PF), now appear likely to provide an improved assessment of the slagging propensity of a coal. Other factors, such as coal volatile yield and nitrogen release, are quite sensitive to the heating conditions. Laboratory tests which match PF combustion conditions much more closely than existing standard methods are now being developed. New approaches to predicting char burnout, by better identification of the small subset of the coal which is actually causing the problem, are also under investigation. While not a general panacea, the appropriate use of new tests is likely to offer engineers involved in coal procurement, who face an increasingly complex market, improved methods for evaluating coals before embarking on expensive pilot- or full-scale trials.
Evaluation of the instantaneous unsteady heat transfer in a rapid compression-expansion machine
Authors: Chen K , Karim G A 
Published: October 2002

Investigation is made of the instantaneous unsteady heat transfer within a pneumatically driven rapid compression-expansion machine that offers simple, well-controlled and known boundary conditions. Values of the instantaneous apparent overall heat flux from the cylinder gas to the wall surfaces were calculated using a thermodynamic analysis of the experimentally measured pressure and volume temporal development. Corresponding heat flux values were also estimated through the application of a three-dimensional computational fluid dynamics code, KIVA3. Correlation of the derived data using the mean piston speed and cylinder bore diameter as the characteristic parameters for the Reynolds and the Nusselt numbers resulted in Nu = 0.010 × Re1.188 for all compression ratios (8.4–24.3). Correlation of the derived data when using the instantaneous height between the piston top and the cylinder head, the maximum gas velocity and the kinetic mean gas velocity obtained when using the KIVA3 code as the characteristic parameters for the Reynolds and the Nusselt numbers was found to produce values of the Nusselt number that were almost independent of the corresponding calculated values of the Reynolds number during the major part of the compression and expansion strokes. A power relationship between the cylinder pressure and gas temperature and the apparent heat transfer coefficient was demonstrated.
A tactile sensing surface for artificial neural network based automatic recognition of the contact force position
Authors: Brett P N , Li Z 
Published: October 2002

The paper describes a new technique for data entry hardware. It is a high-level interpretation method based on the back-propagation neural network model, in which two aspects of research and development works are illustrated in detail: one is a tactile sensing surface comprising a deformable surface with optical sensing elements; the other is the data acquisition and processing model in which a neural network model, called Tactile Position Recognitron, is programmed to realize the real-time and precise recognition of a contact force position, which enables the contact position of a constant force to be determined within an accuracy less than 4 per cent of full scale in a continuous spatial resolution of 35 zones. The device described utilizes a simple low-cost and robust mechanical design combined with software to interpret sensory data to measure the contact position of a normal force applied on a planar surface. The high-level interpretation method for this system enables automatic determination of contact position in real time.
Lubricant properties for input to hydrodynamic and elastohydrodynamic lubrication analyses
Authors: Larsson R , Larsson P. O. , Eriksson E , Sjöberg M , Höglund E 
Published: October 2002

The properties of a number of common lubricants have been measured, namely the viscosity, elastohydrodynamic lubrication (EHL) friction coefficient, density, thermal conductivity and heat capacity per unit volume. These properties have been measured within relatively broad pressure and temperature ranges. The lubricants tested were naphthenic and paraffinic mineral oils, blends of these, polyalphaolefins and a polyglycol. Physical-empirical expressions have been developed upon the basis of the measurement results and a number of lubricant constants, or lubricant parameters, have been determined for each lubricant. These expressions can be used in engineering computational tools for lubrication analysis. The use of such analyses is expected to increase into the new millennium and it is thus important to provide reliable and relevant input data.
Chaotic response of a short journal bearing
Authors: Brown R. D. , Drummond G , Addison P. S. 
Published: October 2002

The non-linear response of fluid-film bearings has been studied for nearly 40 years. Apart from a paper on aperiodic behaviour by Holmes et al. in 1978, much of the work has concentrated on limit cycle behaviour and the practical bounds of linear models. Brindley et al. in 1990 examined the free vibration of a rigid rotor supported by a short bearing oil film. Numerical integration of the equations of motion demonstrated the existence of both large and small limit cycles at operating conditions close to the stability boundary. Hopf bifurcations were shown to exist using a theoretical method. Brindley et al. clearly recognized that the inclusion of unbalance in the model would produce a wider range of behaviour but no results were presented. In recent years the chaotic response of many non-linear systems has received much attention. The main requirements for chaos in a dynamic system are sufficient non-linearity and a minimum of three first-order differential equations. These conditions are satisfied by a rigid journal supported on a hydrodynamic bearing film operating at a high eccentricity. At moderate levels of unbalance the bearing is stable and the behaviour is approximated by a linear treatment. Nevertheless, when the rotating unbalance force exceeds the static load, the bearing is intermittently unloaded and chaos can result. In this paper the region of interest is bounded by three parameters, the dynamic-static force ratio, the operating eccentricity and the non-dimensional frequency ω √ C/g, the latter an established measure of stability. For values of ω √ C/g above 2.5, and eccentricity ratios greater than 0.65 a region of chaos is established for a moderate range of dynamic-static force ratio values. If the unbalance is increased further, the response again becomes periodic, as might be expected. There is a possibility that turbomachinery with heavily loaded bearings may experience chaotic behaviour.
Elastohydrodynamic film formation at the start-up of the motion
Authors: Glovnea R. P. , Spikes H. A. 
Published: October 2002

This paper describes an experimental study of elastohydrodynamic (EHD) lubricating film formation during the start-up of motion of a point contact from rest. EHD film thickness was measured using ultra-thin optical interferometry. It was found that film thickness behaviour depends strongly upon acceleration. When motion starts, most lubricants form a front that travels across the contact with its initial thickness unchanged. At some point, depending upon the acceleration, a second front often forms, so that the lubricant film has a characteristic stepped profile. This behaviour occurs in both pure sliding and pure rolling conditions. The development of film profile over time can be used to chart the speed of motion of the fluid film in the contact. In pure rolling conditions, the first film front travels through the conjunction at a speed lower than the entrainment speed in the first half of the contact and higher in the second half. In pure sliding it travels at a velocity higher than the entrainment speed across the whole width of the contact. The leading edge moves as a core of lubricant with a velocity constant through 60 per cent of its thickness. At very high accelerations, the central film thickness shows damped oscillations about the steady state final entrainment speed value. These oscillations are similar to those found theoretically by other workers for an accelerated slider bearing using a Navier-Stokes analysis. It is believed that some of the non-classical EHD behaviour observed on start-up may result from the finite rate of momentum transfer across the fluid film.