bluuebunny/crossref_metadata_2025 huggingface dataset:
Biomechanical consequences of scaling
Authors: Biewener Andrew A.
Published: April 2005

To function over a lifetime of use, materials and structures must be designed to have sufficient factors of safety to avoid failure. Vertebrates are generally built from materials having similar properties. Safety factors are most commonly calculated based on the ratio of a structure's failure stress to its peak operating stress. However, yield stress is a more likely limit, and work of fracture relative to energy absorption is likely the most relevant measure of a structure's safety factor, particularly under impact loading conditions characteristic of locomotion. Yet, it is also the most difficult to obtain. For repeated loading, fatigue damage and eventual failure may be critical to the design of biological structures and will result in lower safety factors. Although area:volume scaling predicts that stresses will increase with size, interspecific comparisons of mammals and birds show that skeletal allometry is modest, with most groups scaling(l∝d0.89) closer to geometric similarity(isometry: l ∝d1.0) than to elastic similarity (l ∝d0.67) or stress similarity(l ∝d0.5). To maintain similar peak bone and muscle stresses, terrestrial mammals change posture when running, with larger mammals becoming more erect. More erect limbs increases their limb muscle mechanical advantage (EMA) or ratio of ground impulse to muscle impulse(r/R=∫G/∫Fm). The increase in limb EMA with body weight (∝W0.25) allows larger mammals to match changes in bone and muscle area (∝W0.72-0.80) to changes in muscle force generating requirements (∝W0.75), keeping bone and muscle stresses fairly constant across a size range 0.04-300 kg. Above this size, extremely large mammals exhibit more pronounced skeletal allometry and reduced locomotor ability. Patterns of ontogenetic scaling during skeletal growth need not follow broader interspecific scaling patterns. Instead,negative allometric growth (becoming more slender) is often observed and may relate to maturation of the skeleton's properties or the need for younger animals to move at faster speeds compared with adults. In contrast to bone and muscle stress patterns, selection for uniform safety factors in tendons does not appear to occur. In addition to providing elastic energy savings, tendons transmit force for control of motion of more distal limb segments. Their role in elastic savings requires that some tendons operate at high stresses (and strains), which compromises their safety factor. Other `low stress' tendons have larger safety factors, indicating that their primary design is for stiffness to reduce the amount of stretch that their muscles must overcome when contracting to control movement.
Exercise-induced maximal metabolic rate scales with muscle aerobic capacity
Authors: Weibel Ewald R. , Hoppeler Hans
Published: April 2005

The logarithmic nature of the allometric equation suggests that metabolic rate scaling is related to some fractal properties of the organism. Two universal models have been proposed, based on (1) the fractal design of the vasculature and (2) the fractal nature of the `total effective surface' of mitochondria and capillaries. According to these models, basal and maximal metabolic rates must scale as M3/4. This is not what we find. In 34 eutherian mammalian species (body mass Mbranging from 7 g to 500 kg) we found V̇O2max to scale with the 0.872 (±0.029) power of body mass, which is significantly different from 3/4 power scaling. Integrated structure-function studies on a subset of eleven species (Mb 20 g to 450 kg) show that the variation of V̇O2max with body size is tightly associated with the total volume of mitochondria and of the locomotor musculature capillaries. In athletic species the higher V̇O2max is linked to proportionally larger mitochondrial and capillary volumes. As a result, V̇O2max is linearly related to both total mitochondrial and capillary erythrocyte volumes, as well as to their surface areas. Consequently, the allometric variation of maximal metabolic rate is directly related to the scaling of the total effective surfaces of mitochondria and capillaries, thus confirming the basic conjecture of the second fractal models but refuting the arguments for 3/4 power scaling. We conclude that the scaling of maximal metabolic rate is determined by the energy needs of the cells active during maximal work. The vascular supply network is adapted to the needs of the cells at their working limit. We conjecture that the optimization of the arterial tree by fractal design is the result rather than the cause of the evolution of metabolic rate scaling. The remaining question is why the energy needs of locomotion scale with the 0.872 or 7/8 power of body mass.
Problems of allometric scaling analysis: examples from mammalian reproductive biology
Authors: Martin Robert D. , Genoud Michel , Hemelrijk Charlotte K.
Published: April 2005

Biological scaling analyses employing the widely used bivariate allometric model are beset by at least four interacting problems: (1) choice of an appropriate best-fit line with due attention to the influence of outliers; (2)objective recognition of divergent subsets in the data (allometric grades);(3) potential restrictions on statistical independence resulting from phylogenetic inertia; and (4) the need for extreme caution in inferring causation from correlation. A new non-parametric line-fitting technique has been developed that eliminates requirements for normality of distribution,greatly reduces the influence of outliers and permits objective recognition of grade shifts in substantial datasets. This technique is applied in scaling analyses of mammalian gestation periods and of neonatal body mass in primates. These analyses feed into a re-examination, conducted with partial correlation analysis, of the maternal energy hypothesis relating to mammalian brain evolution, which suggests links between body size and brain size in neonates and adults, gestation period and basal metabolic rate. Much has been made of the potential problem of phylogenetic inertia as a confounding factor in scaling analyses. However, this problem may be less severe than suspected earlier because nested analyses of variance conducted on residual variation(rather than on raw values) reveals that there is considerable variance at low taxonomic levels. In fact, limited divergence in body size between closely related species is one of the prime examples of phylogenetic inertia. One common approach to eliminating perceived problems of phylogenetic inertia in allometric analyses has been calculation of `independent contrast values'. It is demonstrated that the reasoning behind this approach is flawed in several ways. Calculation of contrast values for closely related species of similar body size is, in fact, highly questionable, particularly when there are major deviations from the best-fit line for the scaling relationship under scrutiny.
Theoretical stress concentration factors for short flat tension bars with opposite U-shaped notches
Authors: Gomes C J , Troyani N , Morillo C , Gregory S , Gerardo V , Pollonais Y
Published: April 2005

The values of the theoretical stress concentration factors for a number of geometries and loads are available in well-known publications. It is shown here that the reported existing results for the geometry treated herein do not account for the effect of the length of the members in the direction of the applied loads, and it is also shown that shorter lengths may have important effects on the magnitudes of the stress concentration factors, a concept widely used in fatigue applications. The finite-element-determined in-plane theoretical stress concentration factors for short rectangular uniform thickness plates, with opposite U-shaped notches, subjected to uniform tension, for the existing range of the notch radii values as well as for an extended range of these values are reported and are presented in the standard graphical form. Other types of boundary condition have been examined as well in this work with various influences on the stated factor. The transition length concept, the dividing threshold between long and short plates is revised, and the corresponding values are reported as well.
Experimental study of the load distribution in bearings by the method of caustics and the photoelasticity method
Authors: Papadopoulos G. A
Published: April 2005

In this paper the theoretical consideration of the caustics and the photoelasticity due to a concentrated load applied at a point of the straight boundary of the semi-infinite plate was studied. Then, the load distribution in a roller bearing was experimentally determined in terms of caustics and photoelasticity.
Weight function and stress intensity factor for a semi-elliptical surface saddle crack in a tubular welded joint
Authors: Chang E , Dover W. D
Published: April 2005

Owing to the complex geometry and non-uniform stress distribution, it is extremely difficult to obtain an accurate value for the analytical stress intensity factor (SIF) solution for a surface crack in a tubular welded joint. It is usually predicted using three-dimensional T-butt SIF solutions in conjunction with appropriate load-shedding models. The problem with this approach is that the effect of the tube curvature is ignored. Thus it may not represent the accurate stress intensity at the tip of the crack and stress redistribution resulting from the reduction of member stiffness with crack growth. Assuming that the relative influence of the weld toe for the deepest point SIF of a semi-elliptical surface crack in a thin pipe is the same as that for an edge crack of the same depth in a flat plate under the same stress distribution and using the weight function for longitudinal cracks in thin pipes as the reference solution, a new weight function in a closed form has been derived for the deepest point of a semi-elliptical surface crack at the saddle position in a tubular welded T-joint in this study. Based on this weight function and the uncracked T-butt through-wall stress distribution database, a new set of SIF parametric equations has been derived for membrane and bending loading respectively. This set of equations has incorporated the crack aspect ratio influence and the effects of the weld toe including the weld toe angle, weld attachment length, and weld radius. With the hot-spot stress, degree-of-bending values and appropriate load-shedding models, they can be used to predict the deepest point SIFs for semi-elliptical surface saddle cracks in tubular welded T-joints. The curvature effect of tubes to the SIFs is identified by comparing the predictions with three-dimensional T-butt finite element data and the results from three-dimensional T-butt weight-function-based SIF solutions. A comparison of the predictions with tubular joint fatigue test results, especially early crack growth data, has shown that this new SIF solution can work very well with the non-linear moment release model. Together with the extended Du-Hancock aspect ratio development model, they provide a fast SIF calculation procedure for the deepest points of surface saddle cracks during fatigue crack growth in tubular welded joints.
Numerical simulation of the effects of the space-variant blank-holder force and geometrical variables in the deep-drawing process
Authors: Wang L , Lee T. C
Published: April 2005

The increase in quality requirements for the formed products makes it desirable to find an effective way of controlling the process to achieve complex shape products without defects. It has been proven by many researchers that the space-variant blank-holder force can improve the quality of forming to achieve a targeted shape product (no wrinkling, a high drawing depth, less variation in thickness, etc.). In the forming process, the most common problems, tearing and wrinkling, generally result from the strain condition. In this paper the effect on the strain path with various types of space-variant blank-holder force and other geometrical parameters, such as the fillet radius, the blank size, and the clearance between the die and the punch, were compared and analysed. The results showed that the space-variant blank-holder force and some geometrical parameters affect the strain distribution to various extents during the forming process. The parameters influence the negative minor strain much more than the maximum major strain.
Evaluation of stress field parameters for an interface crack in a bimaterial by digital photoelasticity
Authors: Ravichandran M , Ramesh K
Published: April 2005

Photoelastic evaluation of the stress intensity factor (SIF) for a crack in a bimaterial tangential to the interface is hitherto confined to the use of only a singular stress field equation. In this paper, the multi-parameter stress field equations of Deng are simplified for use by experimentalists to evaluate the stress field parameters by digital photoelasticity using an overdeterministic least-squares technique. A bimaterial Brazillian disc with a central interface crack is selected as the model for study as different mode mixities could be easily simulated by changing the crack orientation angle. The use of SIF evaluation based on a singular stress field equation is found to be inadequate for the problems considered. On the other hand, the use of a multi-parameter stress field equation is quite successful in evaluating the stress field for various mode mixities and for two values of bimaterial constant. It is shown that the new procedure allows data collection from a larger zone, which helps to simplify data collection from experiments.
The flame behaviour of liquefied petroleum gas spray impinging on a flat plate in a constant volume combustion chamber
Authors: Park Kweonha
Published: April 2005

Liquefied petroleum gas (LPG) sprays and diffusion flames are investigated in a constant volume combustion chamber having an impingement plate. The spray and flame images are visualized and compared with diesel and gasoline images over a wide range of ambient pressure. The high-speed digital camera is used to take the flame images. The injection pressure is generated by a Haskel air-driven pump, and the initial chamber pressure is adjusted by the amount of pumping air. The LPG spray and flame photographs are compared with those of gasoline and diesel fuel at the same conditions, and then the spray and flame development behaviour is analysed. The spray photographs show that the dispersion characteristics of LPG spray are sensitive to the ambient pressure. In a low initial chamber pressure LPG fuel in the liquid phase evaporates quickly and does not reach down easily to the impinging plate having a hot coil for ignition. That makes the temperature and equivalence ratio low near the ignition coil, thus making ignition diffcult. On the other hand, in a high initial chamber pressure the spray leaving the nozzle gathers around the ignition site after impinging on the plate, which makes an intense flame near the plate. If applied to small-sized direct injection engines that are not able to avoid spray impinging on a cylinder wall, LPG will have faster and cleaner combustion than diesel or gasoline fuels. However, the chamber geometry should be carefully designed to enable a sufficient amount of vaporized fuel to get to the ignition site
Model-matching control applied to longitudinal and lateral automated driving
Authors: Kwon Seong-Jin , Fujioka Takehiko , Cho Ki-Yong , Suh Myung-Won
Published: April 2005

Although there has been substantial research on longitudinal and lateral controllers for an automated driving system, stability issues with respect to the effect of uncertainties due to parameter variations (e.g. in the vehicle mass and the cornering stiffness) and disturbances or perturbations to the vehicle system (e.g. in the road gradient and the wind) still need to be addressed. Thus, an automated driving system needs to be made robust to those influences.

For this purpose, the model-matching control applied to longitudinal and lateral automated driving is investigated by vehicle dynamics simulation. The design of the model-matching controller is obtained by using the characteristics of a two-degree-of-freedom controller. It can make various characteristics of automated driving vehicles equivalent to a specific transfer function, which is suggested as the reference model.

The vehicle dynamics models including the model-matching controller are constructed for computer simulation. Then, simple examples of open-loop simulation and closed-loop simulation are solved to check the robustness of the model-matching controller. As a practical example, an automated driving system is adopted. It is proved that the model-matching control is effective and adequate for uncertainties due to parameter variation and disturbances or perturbations to the vehicle system, which are shown in the responses of the changes in the vehicle mass, the road gradient and the cornering stiffness.
Vibration analysis of a vehicle system supported on a damper-controlled variable-spring-stiffness suspension
Authors: Ghosh M K , Dinavahi R
Published: April 2005

Vibration isolation performance has been investigated for a vehicle system supported on a damper-controlled variable-spring-stiffness suspension system. A half-car model has been analysed for different values of damping ratio, relative damping ratio, and mass ratio. The semi-active control of a half-car model has been investigated with the help of a force generator as well as with optimal control theory.

The results show that a damper-controlled variable-stiffness suspension improves the vibration isolation performance of the suspension system. It has been found that a lower damping ratio, a relative damping ratio of unity, and a higher mass ratio gives optimum reduction in the transmissibility of motion from road surface to the vehicle body.

The semi-active control of a half-car model supported on a damper-controlled variable-springstffiness suspension can be achieved using a force generator or an actuator. The use of a force generator can minimize the power required to control the damper. A full-state feedback and linear quadratic regulator control theory gives better results for higher mass ratios.
The effect of fuel octane and dilutent on homogeneous charge compression ignition combustion
Authors: Atkins M J , Koch C R
Published: April 2005

This paper presents some experimental operating and combustion properties of homogeneous charge compression ignition (HCCI) combustion. HCCI operating range, start of combustion, burn duration, indicated mean effective pressure, indicated specific emissions, and indicated specific fuel consumption are evaluated as charge dilution and octane number are varied. Primary reference fuels with octane numbers of 20, 40, and 60 are used in this study. The autoignition properties of the air-fuel mixture are varied by changing the fuel octane number, percentage of exhaust gas recirculation (EGR), and air-fuel ratio, while holding the intake temperature, engine speed, and compression ratio constant. Results show that both the start of combustion and the burn duration are sensitive to mixture dilution (excess air or EGR). The fuel octane number is not an effective method of controlling the start of combustion or the burn duration but can be used to increase the load range of the HCCI engine. Both the NO x emissions and the indicated specific fuel consumption increase as the octane number is increased due to lower dilution and higher peak temperatures. Correct amounts of dilution are critical in controlling HCCI combustion. Separating dilution into EGR and excess air, it is found that a given amount of EGR is more effective at controlling the start of combustion and the burn duration than the same amount of excess air.
Experimental investigations of the effect of biodiesel utilization on lubricating oil tribology in diesel engines
Authors: Agarwal A K
Published: April 2005

Biodiesel is an alternative fuel derived from vegetable oils by modifying their molecular structure through a transesterification process. Linseed oil methyl ester (LOME) was prepared using methanol in the presence of potassium hydroxide as a catalyst. The use of LOME in compression ignition engines was found to develop a very compatible engine-fuel system with lower emission characteristics. Two identical engines were subjected to long-term endurance tests, fuelled by an optimum biodiesel blend (20 per cent LOME) and diesel oil, respectively.

Various tribological studies on lubricating oil samples drawn at regular intervals from both engines were conducted in order to correlate the comparative performance of the two fuels and the effect of fuel chemistry on lubricating oil performance and life. A number of tests were conducted in order to evaluate the comparative performances of the two fuels such as density measurement, viscosity measurements, Flashpoint determination, moisture content determination, pentane and benzene insolubles, thin layer chromatography, differential scanning calorimetry, etc. All these tests were used for an indirect interpretation of the comparative performance of these fuels. The performance of biodiesel fuel is found to be superior to that of diesel oil and the lubricating oil life is found to be longer while operating the engine on biodiesel
Eco-diesel engine fuelled with rapeseed oil methyl ester and ethanol. Part 1: Efficiency and emission
Authors: Kowalewicz A
Published: April 2005

A novel concept of fuelling a diesel engine with biofuels - rapeseed oil methyl ester (RME) and ethanol was proposed, developed, and investigated. The idea of the concept depends on standard fuelling with RME and additional injection of ethanol into the inlet port during the inlet stroke. After ignition from burning RME droplets, the ethanol-air mixture burns very quickly and promotes combustion of the main fuel droplets. This results in a shorter combustion period. Experiments were carried out with the use of a one-cylinder direct injection diesel engine adapted to ethanol injection at three speeds and two loads: low and high and for three injection timings. At each experimental point the proportion of ethanol to RME was changed from zero to the value at which diesel knock occurred in such a way that the engine load was kept constant. This showed the influence of the ethanol energy to total fuel energy ratio (ΩE) on effciency and emissions (ΩE was a main independent variable parameter). A considerable decrease in CO2 and the smoke level was obtained and, for high loads also CO and HC emissions. At low loads the NOx emissions were reduced. The optimum ratio of ethanol energy to total fuel energy, in terms of brake fuel conversion effciency and benefit of emission decrease, was found to be about 25 per cent.
Economic Theory and Experimental Economics
Authors: Samuelson Larry
Published: April 2005

This paper explores the questions of how economic theory can be used to design and interpret experiments and how experimental results can be used to construct and interpret economic theories. The relationship between economic theory and experiments is modeled and illustrated with examples from both theoretical and experimental work. The emphasis is on combing theory and experiment to the benefit of both.
Development
Authors: Schumpeter Joseph A , Eßlinger Hans Ulrich , Hedtke Ulrich
Published: April 2005

The present article introduces Development, a new, unpublished and hitherto unknown article by Joseph A. Schumpeter from 1932. Development is remarkable because it significantly adds to Schumpeter's known works on a number of issues that were central to his theory of economic development. Development shows that Schumpeter considered the explanation of novelty as the most important unsolved scientific problem. Schumpeter doubts the explanatory value of entrepreneurship and indicates that theoretical advances might be forthcoming that can help a better understanding of the social dynamics which gives rise to novelty.
Neuroeconomics: How Neuroscience Can Inform Economics
Authors: Camerer Colin , Loewenstein George , Prelec Drazen
Published: April 2005

Neuroeconomics uses knowledge about brain mechanisms to inform economic analysis, and roots economics in biology. It opens up the “black box” of the brain, much as organizational economics adds detail to the theory of the firm. Neuroscientists use many tools— including brain imaging, behavior of patients with localized brain lesions, animal behavior, and recording single neuron activity. The key insight for economics is that the brain is composed of multiple systems which interact. Controlled systems (“executive function”) interrupt automatic ones. Emotions and cognition both guide decisions. Just as prices and allocations emerge from the interaction of two processes—supply and demand— individual decisions can be modeled as the result of two (or more) processes interacting. Indeed, “dual-process” models of this sort are better rooted in neuroscientific fact, and more empirically accurate, than single-process models (such as utility-maximization). We discuss how brain evidence complicates standard assumptions about basic preference, to include homeostasis and other kinds of state-dependence. We also discuss applications to intertemporal choice, risk and decision making, and game theory. Intertemporal choice appears to be domain-specific and heavily influenced by emotion. The simplified ß-d of quasi-hyperbolic discounting is supported by activation in distinct regions of limbic and cortical systems. In risky decision, imaging data tentatively support the idea that gains and losses are coded separately, and that ambiguity is distinct from risk, because it activates fear and discomfort regions. (Ironically, lesion patients who do not receive fear signals in prefrontal cortex are “rationally” neutral toward ambiguity.) Game theory studies show the effect of brain regions implicated in “theory of mind”, correlates of strategic skill, and effects of hormones and other biological variables. Finally, economics can contribute to neuroscience because simple rational-choice models are useful for understanding highly-evolved behavior like motor actions that earn rewards, and Bayesian integration of sensorimotor information.

Who knows what I want to do? Who knows what anyone wants to do? How can you be sure about something like that? Isn't it all a question of brain chemistry, signals going back and forth, electrical energy in the cortex? How do you know whether something is really what you want to do or just some kind of nerve impulse in the brain. Some minor little activity takes place somewhere in this unimportant place in one of the brain hemispheres and suddenly I want to go to Montana or I don't want to go to Montana. (White Noise, Don DeLillo)
The new GMS contract: impact and implications for managing the changes
Authors: Spurgeon Peter , Hicks Carolyn , Field Stephen , Barwell Fred
Published: April 2005

Background: In February 2003, a new General Practitioner (GP) contract was agreed between the profession's leaders and the government, which was later accepted following a national ballot of GPs. However, the ballot simply required respondents to vote for or against the proposal; it did not provide any opportunity to identify which aspects of the new contract were more or less acceptable. Since the proposed changes were far reaching, the implications of implementing and managing these were considerable. Consequently, some information about how GPs viewed various components of the new contract would enable a more targeted and effective management strategy to be developed that would facilitate the introduction of all aspects of the contract.

Objectives: To survey GPs working within the West Midlands region regarding their opinions on each of the key features of the new contract.

Method: A postal survey of 360 GPs was undertaken, using a specially devised questionnaire.

Results: Four factors emerged as the most acceptable aspects of the contract: option to opt out of out-of-hours work, flexibility in the services provided, prediction of future income levels and linking practice to performance targets. Least acceptable were: performance monitoring systems, the new financial formula for calculating income, greater patient involvement in service development and 24/48 hour access. With regard to potential outcomes of the contract, the most positive were considered to be increased proportion of salaried GPs, increased salaries, appropriate quality standards for care, earlier retirement; the factors least likely to be of potential benefit were: reduction in occupational stress, simplification of the regulatory framework, improved equity of workload and improved staff retention. Further analysis of the results using inferential statistics revealed a range of subgroup differences in reaction to the contract.

Conclusion: Overall, those aspects of the new contract that are perceived to reduce workload and enhance salary were supported, while those that increase targets and bureaucracy were not. Generally, there was only moderate support for the changes, which could be explained by a general scepticism about any top-down modifications, the practicality and power of the changes to impact upon practice and/or a genuine belief that the modifications are unacceptable. Taken together, these results provide an indicative focus for managing the implementation of the new contract, especially with regard to its least acceptable components and the emerging differences between subgroups of GPs.
From the trenches: views from decision-makers on health services priority setting
Authors: Patten San , Mitton Craig , Donaldson Cam
Published: April 2005

Due to resource scarcity, health organizations worldwide must decide what services to fund and, conversely, what services not to fund. One approach to priority setting, which has been widely used in Britain, Australia, New Zealand and Canada, is programme budgeting and marginal analysis (PBMA). To date, such activity has primarily been based at a micro level, within programmes of care. In order to institute and refine the PBMA framework at a macro level across major service areas within a single health authority, researchers and decision-makers in Alberta embarked on a participatory action research project together.

This paper identifies key issues of importance to decision-makers in a real-world priority-setting context. Themes discussed include making comparisons across disparate patient groups, dealing with political factors, using relevant forms of evidence, recognizing innovations and involving the public. The in-depth insight gained through this qualitative analysis will enable future refinement of PBMA at a macro level in the health authority under study, and should also serve to inform priority-setting activity in regionalized contexts elsewhere. In identifying aspects of priority setting that are important to decision-makers, researchers can also be better informed with respect to realworld processes.
Using the balanced scorecard to characterize benefits of integration in the safety net
Authors: Wells Rebecca , Weiner Bryan
Published: April 2005

The purpose of this study was to develop a comprehensive framework depicting the potential benefits of integration among health-care providers that serve vulnerable populations. Research teams interviewed participants in 12 integrated functions across seven community health-centre-led networks. Functions included clinical processes; managed care contracting; and administrative services such as human resources, finance, and information systems. Using a Balanced Scorecard framework, benefits were identified across financial, customer, internal business, and learning and growth perspectives. Financial benefits were more frequently cited relative to managed care and administrative functions than relative to clinical functions. Clinical functions were frequently characterized by perceived improvements in patient care quality, while managed-care functions appeared to yield most benefits in access. Administrative functions were most often associated with improvements in internal business operations. There were substantial findings in learning and growth across all three types of integration, in keeping with the early stages of the integrated functions in the study. Findings imply that integration among health-care providers yields a wide range of benefits, but not necessarily quickly or financial in nature.
Strategies for multi-hospital networks: a framework
Authors: Lega Federico
Published: April 2005

The last two decades have seen the significant emergence of multi-hospital networks (MHNs) in the health sectors of all industrialized countries. Such networks seem to represent an organizational choice, which provides interesting opportunities to cope with cost and quality issues stressing the health field. This work proposes and discusses a framework for strategies that can be implemented by MHNs to achieve projected benefits. The estimated advantages are then weighed against unexpected or underrated drawbacks and empirical evidence. The conclusions point out MHNs as viable future alternatives for freestanding hospitals looking to improve their efficiency and financial stability, on condition that a 'proper management' of their consolidation processes is carried out. This requires extensive pre-deal analysis to critically assess what benefits could be achieved through the network's formation, as well as post-deal perseverance in implementing consolidation strategies to their full. In this perspective, specific advices apt to minimize the risk of creating MHNs in the wake of a management fashion instead of through sound rational assessments are also discussed.
Towards an organization with a memory: exploring the organizational generation of adverse events in health care
Authors: Smith Denis , Toft Brian
Published: April 2005

The role of organizational factors in the generation of adverse events, and the manner in which such factors can also inhibit an organization's abilities to learn, have become important agenda items within health care. The government report 'An organization with a memory' highlighted many of the problems facing health care and suggested changes that need to be made if the sector is to learn effective lessons and prevent adverse events from occurring. This paper seeks to examine some of these organizational factors in more detail and suggests issues that managers need to consider as part of their wider strategies for the prevention and management of risk. The paper sets out five core elements that are held to be of importance in shaping the manner in which the potential for risk is incubated within organizations. Although the paper focuses its attention on health care, the points made have validity across the public sector and into private sector organizations.
On the Reduction of Ammonia from the Waste of Alpine Houses
Authors: Al-Asheh Sameer , Bischof Franz
Published: April 2005

An evaluation of the effectiveness of the cation-exchange resin Amberlite IR-120 (AMIR 120) for removing ammonia from aqueous solutions and waste was made. Two types of waste were obtained from houses located in the Alps and used in this work. The results of the study showed that AMIR 120 may be considered as a suitable material for the removal of ammonia from aqueous and waste systems. The amount of ammonia removed increases with increasing AMIR 120 concentration. Sorption of ammonia decreases as the pH of the aqueous solutions increases. The Langmuir model represents the experimental data reasonably well.
Effect of Complex Terrain on Vertical Wind Profile Measured by SODAR Technique
Authors: Maeda Takao , Homma Shuichiro , Ito Yoshiki
Published: April 2005

This paper describes the effect of terrain configuration on the atmospheric boundary layer for siting large wind turbines, based on data from Doppler SODAR. Prior to installing large machines, standard meteorological anemometers, to about 30 m height, are cost effective and relatively easy to install for an approximate extrapolated wind assessment. However, if accurate wind assessment is needed, the wind condition at hub height of more than 50 m should be measured directly, especially in complex terrain. The data presented in this paper were collected from a measurement site located at the coast of the Japan Sea. Comparison is made between data measured at hub-height by Doppler SODAR and the data predicted from observation of the wind condition at lower height. A significant difference is noted between the extrapolated results from lower level measurements and the results directly measured by SODAR, especially when the wind is over complex terrain. Thus it is shown that wind speed measurement at low height is not satisfactory for assessing wind accurately at rotor height, but that Doppler SODAR measurement is satisfactory.
A Static VAR Compensator Model for Improved Ride-Through Capability of Wind Farms
Authors: Akhmatov Vladislav , Søbrink Kent
Published: April 2005

Dynamic reactive compensation is associated with reactive power and voltage control of induction generator based wind turbines. With regard to wind power, application areas of dynamic reactive compensation can be improvement of the power quality and the voltage stability, the control of the reactive power exchange between the wind farm and the power grid in the wind farm connection point as well as improvement of the ride-through capability of the wind farm. This article presents a model of a Static VAR Compensator (SVC) with dynamic generic control that is a kind of dynamic reactive compensation devices. The term “generic” implies that the model is general and must cover a variety of the SVC units and their specific controls from different manufacturers. The SVC model with dynamic generic control is implemented by Eltra in the simulation tool Powerfactory and validated from the SVC model in the tool PSCAD/EMTDC. Implementation in the tool Powerfactory makes it possible to apply the SVC model with dynamic generic control in investigations of power system stability with regard to establishment of large wind farms without restrictions on the model size of the power grid.
Effect of Site Wind Properties on Wind-Electric Conversion Costs
Authors: Pallabazzer Rodolfo
Published: April 2005

The unit cost of energy production of windgenerators is examined by means of a model of the turbine power curve and the Weibull model of wind probability function, by applying the usual economic equations. The analysis is carried out in terms of dimensionless variables whose range of variability is defined by examining the data of 80 modern commercial wind turbines; likewise, the economic parameters are based on the present state of costs. The unit cost decreases asymptotically when α (ratio between mean wind speed and cut-in speed) – increases and shows a lower limit of 2 to 5 €cent/kWh. This cost depends both on the value of the machine parameter φ (ratio between nominal and cut-in speed) and on the basic prices. The effect of the Weibull shape parameter k is different according to the values of α and φ: with low α and high φ the unit cost increases along with k (that is with the regularity of the winds); the more α increases the less k affects the unit cost.

The sensitivity analysis shows that the windgenerator cost is the strongest term, and that α and φ are also significant. The saving from choosing the optimised wind turbine can be 1 to 6 €cent/kWh. The analysis of increasing the hub height shows financial benefit is not assured, as it can be positive or negative depending on the values of α, φ and the ground roughness.
Fan Interaction Noise Predictions Using RANS-BEM Coupling
Authors: Polacsek C. , Burguburu S.
Published: April 2005

A source-to-far-field computation procedure aiming at predicting the noise generated by rotor-stator fan interactions and inlet noise radiation is presented here. It is applied to the NLR turbofan model, tested in DNW-LLF anechoic chamber under the framework of DUCAT project. The unsteady aerodynamic input for the acoustic computation is obtained using a 3D RANS code, CANARI, developed at ONERA for turbomachinery applications. The CFD solutions are coupled, using a modal expansion approach, to a BEM code, solving the Helmholtz equation in an arbitrary bounded space. A single interacting cut-on mode amplitude is either directly deduced from experiment or provided by post-processing the CFD data. With this approach, the predicted noise radiation can be related to the directivity patterns measured at several axial positions upstream of the turbofan inlet. A fairly good agreement is found using both experimental and CFD input data.
The Acoustic Spectrum in the Sound Field of Isotropic Turbulence
Authors: Lilley Geoffrey M.
Published: April 2005

Lighthill's theory of Aerodynamic Noise uses an acoustic analogy by which the equivalent acoustic sources in a turbulent flow have first to be calculated, measured or modeled from a time-accurate evaluation of the unsteady flow. Proudman considered the application to the noise radiated from weakly compressible isotropic turbulence, by evaluating the fourth-order space-time covariance of Lighthill's stress tensor. The resulting acoustic power per unit volume of turbulence was found to follow the eighth power law of velocity and showed the efficiency of conversion of turbulent kinetic energy into sound was extremely small, being proportional to the fifth power of the turbulent Mach number. These results are of particular interest today, since, all turbulent shear flows were shown by Kolmogorov to become locally isotropic near the dissipation range. Hence the high frequency asymptotic far-field radiated noise spectrum generated from eddies in the inertial subrange of all turbulent shear flows should obey a universal frequency law as obtained from isotropic turbulence, namely f−7/ 2, a result first found by Meecham and Ford. From studies of the fluctuations in this nonlinear energy transfer cascade from large to small eddies it is possible to gain a better insight as to the physical process, and the reason for its weak efficiency, whereby sound is generated and radiated as a broadband spectrum. A key factor is shown to be the weak fluctuations in the rate of dilatation in the compressible turbulent flow, which explains the reason for the efficiency of sound conversion obtained by Lighthill.
A Splitting Method for Aeroacoustic Noise Prediction of Low Mach Number Viscous Flows
Authors: Moon Young J. , Seo J. H.
Published: April 2005

A set of perturbed compressible equations(PCE), based on a hydrodynamic/acoustic splitting method, is proposed for aeroacoustic noise prediction of low Mach number viscous flows. The present formulation corrects the deficiency of previous splitting methods that have no control over the coupling effects between the incompressible vorticity and the perturbed velocities. The validation test shows that the present PCE solution is in excellent agreement with those of direct acoustic numerical simulation(DaNS) and Curle's acoustic analogy for a laminar dipole tone from a 2D circular cylinder at Reynolds number based on the cylinder diameter, ReD=200 and free stream Mach number, M∞ = 0.3. Computational efficiency and accuracy requirements for PCE are also investigated for a vortex scattering noise from the trailing-edge of a thin plate at Reynolds number based on the plate thickness, Reh= 2000 and M∞ = 0.3. The test results indicate that the computational efficiency can be achieved with an acoustic grid at lower resolution, as long as the projection quality of the total derivative of the incompressible pressure, DP/Dt field is retained.
Spatial Stability Analysis of a Flap Side Edge Vortex
Authors: Brazier Jean-Philippe , Moens Frédéric , Bardoux Philippe
Published: April 2005

The flap side edge vortex is suspected to contribute to aerodynamic noise generation. Using a temporal stability analysis, Khorrami and Singer have shown that unstable modes could exist in this vortex. Due to the convective nature of this instability, a spatial analysis is more suitable. This is the subject of the present work. The mean flow past a 2D wing with a half-span flap has been computed with a steady 3D Navier-Stokes code. Then, local linear stability calculations are performed in several planes perpendicular to the vortex axis. The vortex is assumed axisymmetric and modelled with Batchelor's analytical vortex. Using Gaster's relation, the spatial amplification rate is calculated, giving by integration the relative amplitude of the fluctuations. Some low-frequency fluctuations are seen to be preferentially amplified by the vortex, but the amplifications remain small, so that this mechanism alone should not produce important noise in this particular configuration, where the flap deflection angle is moderate.
The detection of loose bodies in the elbow
Authors: Dubberley J. H. , Faber K. J. , Patterson S. D. , Garvin G. , Bennett J. , Romano W. , MacDermid J. C. , King G. J. W.
Published: April 2005

Our aim was to determine the clinical value of MRI and CT arthrography in predicting the presence of loose bodies in the elbow.

A series of 26 patients with mechanical symptoms in the elbow had plain radiography, MRI and CT arthrography, followed by routine arthroscopy of the elbow. The location and number of loose bodies determined by MRI and CT arthrography were recorded. Pre-operative plain radiography, MRI and CT arthrography were compared with arthroscopy.

Both MRI and CT arthrography had excellent sensitivity (92% to 100%) but low to moderate specificity (15% to 77%) in identifying posteriorly-based loose bodies. Neither MRI nor CT arthrography was consistently sensitive (46% to 91%) or specific (13% to 73%) in predicting the presence or absence of loose bodies anteriorly. The overall sensitivity for the detection of loose bodies in either compartment was 88% to 100% and the specificity 20% to 70%. Pre-operative radiography had a similar sensitivity and specificity of 84% and 71%, respectively.

Our results suggest that neither CT arthrography nor MRI is reliable or accurate enough to be any more effective than plain radiography alone in patients presenting with mechanical symptoms in the elbow.
Prognostic factors and a scoring system for patients with skeletal metastasis
Authors: Katagiri H. , Takahashi M. , Wakai K. , Sugiura H. , Kataoka T. , Nakanishi K.
Published: April 2005

Between 1992 and 1999, we treated 350 patients with skeletal metastases. A multivariable analysis of the patients was conducted using the Cox proportional hazards model. We identified five significant prognostic factors for survival, namely, the site of the primary lesion, the performance status (Eastern Cooperative Oncology Group status 3 or 4), the presence of visceral or cerebral metastases, any previous chemotherapy, and multiple skeletal metastases. The score for each significant factor was derived from the corresponding estimated regression coefficients (natural logarithm of the hazard ratio). The prognostic score was calculated by adding all the scores for individual factors.

The rate of survival was 31% at six months and 11% at one year for the patients with a prognostic score of 6 or more. By contrast, patients with a prognostic score of 2 or less had a rate of survival of 98% at six months and 89% at one year. This scoring system can be used to determine the optimal treatment for patients with pathological fractures or epidural compression.