bluuebunny/crossref_metadata_2025 huggingface dataset:
The modelling and simulation of vehicle handling Part 1: Analysis methods
Authors: Blundell M V
Published: October 2002

This is the first in a series of four papers looking at the application of computer-based analysis methods to model vehicles and simulate vehicle handling. The material contained in these papers is based on a study carried out in order to investigate the influence of suspension and tyre modelling on the outputs predicted by vehicle handling simulations. The papers deal with analysis methods, vehicle modelling, tyre modelling and handling simulation.

In this paper a review is provided that outlines some of the main contributions leading to the development of models and tools in vehicle dynamics, followed by an overview of the computer-based simulation methodology known as multi-body systems analysis. The way in which multi-body systems analysis can be used to generate models, formulate and solve the equations of motion and post-process the results will be discussed. The examples used to illustrate the concepts explained throughout this series of papers have been generated using the ADAMS (Automatic Dynamic Analysis of Mechanical Systems)program.
Mechanics of materials: A materials science perspective
Authors: Roylance D , Cohen K C , Jenkins C H , Khanna S K
Published: October 2002

Mechanics of materials subjects in the engineering curricula obviously involve both mechanics and materials concepts, but many such subjects have become overly concentrated on mechanics at the expense of materials. A stronger linkage between the two disciplines could improve both efficiency and student learning. Some examples are provided to illustrate how a better balance might be restored; the examples are based on a recent textbook and subject developed at the Massachusetts Institute of Technology (MIT). Student evaluations have shown this approach to be well received, although there is room for improvement.
Linking design with structural mechanics and materials
Authors: Jenkins C H , Khanna S K , Roylance D
Published: October 2002

Educating students in the design of structures has been strongly influenced in modern times by specialization. What in the development of real structures should be an interwoven activity of design, mechanics analysis and materials selection, has been reduced in academic training to three separate activities—leaving the student to work out how to accomplish the integration. It is much easier to teach these subjects in isolation from one another, but the student, and ultimately society as a whole, are left the poorer for it. This paper presents a new approach to teaching structural design. The method centres on the use of a design template, which defines the design space through design degrees of freedom. Within the design template, mechanics analysis and material selection take place in a concurrent fashion. These concepts are discussed in the paper and an example illustrating their use is provided.
Spray propagation and mixture formation in an air guided direct injection gasoline engine
Authors: Adomeit P , Lang O , Pischinger S
Published: October 2002

Numerical analysis is used to gain information on the spray propagation and mixture formation in tumble guided gasoline direct injection (DI) engines. In order to achieve reliable predictions an atomization model for high-pressure swirl injectors is described and verified by comparison to experimental data. The approach is capable of adequately predicting the most important effects, such as nozzle orifice diameter, cone angle or injection pressure on spray development. Furthermore, it is found that the pre-jet generated at the beginning of the injection strongly affects the overall spray development. The temporal development of the pre-jet is described empirically.

The in-cylinder computational fluid dynamics (CFD) analysis reveals that the tumble charge motion strongly affects spray propagation and mixture formation in the stratified operation mode, as it transports the fuel vapour cloud towards the spark plug. The CFD simulation improves understanding of the interaction between the flow field, spray propagation and evaporation and enables guidance of the optimization of the flow control and of the injection parameters for tumble guided gasoline DI engines.
The effect of the stroke-to-bore ratio on combustion, heat transfer and efficiency of a homogeneous charge spark ignition engine of given displacement
Authors: Filipi Z. S. , Assanis D. N.
Published: October 2002

This study investigates how the selection of the stroke-to-bore (S/B) ratio affects combustion, heat transfer and overall efficiency in a homogeneous charge spark ignition (SI) engine of a given displacement. Initially, flame front area maps and wall areas in contact with burned gases are examined from a purely geometric point of view, for S/B ratios of 0.7, 1.0 and 1.3. Subsequently, a quasi-dimensional turbulent flame entrainment model is used to quantify the extent to which turbulence versus geometric factors are responsible for the observed combustion, heat transfer and cycle efficiency behaviour, as the S/B ratio varies. Calculations are performed for a range of engine speeds and loads, as well as for operation with 15 per cent exhaust gas recirculation (EGR). Results show that the S/B ratio has a significant effect on both turbulence levels and the geometric interaction of the flame front with the combustion chamber walls. In general, a longer stroke leads to higher thermal efficiency through faster burning and lower overall chamber heat loss. These effects are non-linear, being more dramatic when the S/B ratio is increased from below unity than from above unity. The potential of the long-stroke engine for brake fuel economy improvement can be exploited to the fullest at low speeds, while friction losses gradually diminish it at higher speeds.
An approach to characterization and after-treatment of particulate emissions from gasoline engines
Authors: Bouris D , Crane R I , Evans J M , Tippayawong N
Published: October 2002

The growing importance of understanding and controlling particulate emissions from gasoline engines is outlined, and an experimental simulation approach is described which has the potential for exploring particle deposition/capture and oxidation phenomena under well-controlled conditions, thus avoiding some of the uncertainties involved in interpreting engine experiments. Artificially generated sub-100 nm carbon particles are introduced into a synthetic exhaust gas stream, simulating engine-out soot emissions. Initial experiments in insulated pipe flows have shown very little particle deposition or change in mean size for residence times up to 1–2 s at uniform temperatures up to 400°C and hydrocarbon concentrations up to 4000 ppm C1′ in line with the results of supporting analytical and computational studies. Further numerical predictions suggested that it might be possible to capture some 20–30 per cent of the particles by turbulent diffusion alone at higher gas flowrates more representative of those in engine exhaust pipes. The effect of two different catalysts and an uncoated monolith on particle size and concentration has been investigated at space velocities of 50000 and 100000 h−1, with an inlet gas temperature of 400°C. Particle penetration through the catalysts increased with particle size but in all cases exceeded 70 per cent, with no evidence of significant changes in particle mean size. In the next phase of experimental and modelling work, the contribution of thermophoresis to particle deposition in uninsulated pipes will be examined.
Effects of oxygenated blending compounds on emissions from a turbocharged direct injection diesel engine
Authors: Litzinger T , Stoner M , Hess H , Boehman A
Published: October 2002

An experimental investigation was conducted to evaluate the effect of three different oxygenated compounds, diglyme, diethyl maleate and dibutyl maleate, on emissions from a Volkswagen 1.9 litre, turbocharged, direct injection diesel engine. Sampling was performed using a mini-dilution tunnel technique to obtain particulate matter and a Fourier transform infrared (FTIR) spectrometer for gaseous emissions. The particulate samples were analysed using thermal analysis and Soxhlet extraction to determine the fraction of volatile and soluble organic material respectively. All three oxygenated compounds were found to be effective at reducing particulate emissions, with the maleate compounds being more effective overall than the diglyme. Analysis of the relative contributions of changes in the soot and soluble organic fraction (SOF) to the reduction of particulate matter indicated that, for diethyl maleate and diglyme, reductions in soot were the dominant effect. No consistent trends in NOx emissions were observed, although the diethyl maleate, which was most effective at reducing the particulate matter, increased the NOx slightly at most of the test conditions. Differences in the combustion chemistry of the additives are discussed as a possible explanation of the greater effectiveness of the maleate compounds in reducing soot, as well as for the difference in the effectiveness of diethyl and dibutyl maleate.
Modelling and experiment of impingement and atomization of a liquid spray on a wall
Authors: Trujillo M. F. , Mathews W. S. , Lee C. F. , Peters J. E.
Published: October 2002

An experimental and computational investigation of spray impingement on a flat surface is presented. Different angles of incidence are studied, namely 30, 45 and 60°C measured from the normal to the surface. Back-lit photographs of the wall spray taken at various times during the impingement period give a qualitative view of the secondary atomization process. A stochastic model based on the sampling of velocity and size distributions of secondary droplets is used to simulate the creation of incident droplet fragments created by the numerous splashing events occurring during the impingement period. Size characteristics of the secondary droplet cloud are computed at various points in the impingement region and these are compared against phase/Doppler particle analyser (P/DPA) measurements yielding reasonable agreement. The effect of surface roughness is incorporated into the model and is found to play a major role in affecting the splashing threshold and the sizes of splashing fragments. The secondary droplet distributions are virtually unchanged among the different angles of incidence. This behaviour is explained by considering the shift in the splashing droplet distribution as a function of incident angle.
A phenomenologically based computer model to predict soot and NOx emission in a direct injection diesel engine
Authors: Gao Z , Schreiber W
Published: October 2002

A phenomenological model based on the multizone method is described. The model requires a relatively low amount of central processing unit (CPU) time and memory for each run and, consequently, is useful for parameter studies. The flame morphology predicted by the model is compared to that recently uncovered in experimental studies. As a demonstration of its utility, the model is used to study the effect of the oxygen content in intake air on the emission of particulate matter (PM) and NOx from a direct injection diesel engine. A parametric study reveals that while oxygen-enriched intake air is useful for reducing PM, the reduction comes with a large increase in NOx emission. The PM-NOx trade-off curve for the oxygenated intake air is worse than that for the baseline air case.
Influence of physical and chemical properties of biodiesel fuels on injection, combustin and exhaust emission characteristics in a direct injection compression ignition engine
Authors: Yamane K , Ueta A , Shimamoto Y
Published: October 2002

This paper describes two topics. One is a study of the effects of biodiesel fuel physical properties on injection characteristics and spray behaviour. The study was done via numerical simulation of the injection system and via laser-sheet imaging of the spray. The second topic is a study of the effects of the constituents of biodiesel fuel on combustion and exhaust emission characteristics in a retrofitted compression ignition engine, as well as combustion under high injection pressure. A critical difference between the gas oil and biodiesel fuel properties is the dependence of the bulk modulus on pressure and temperature. Computation results show that at lower fuel temperatures, the injection timing of biodiesel is effectively advanced relative to that of gas oil. This is because at lower liquid temperatures the bulk modulus of biodiesel fuel is higher than that of gas oil; then the rate of liquid pressure rise goes up and the injection timing is advanced. At higher fuel temperatures, there is no difference in the injection timing and the injection pressure between biodiesel fuel and gas oil. Engine measurements showed that at low engine load, the exhaust particulate matter (PM) using biodiesel contained a higher level of soluble oragnic fraction (SOF) than that using gas oil. This result was related to the results of spray visualization. It was found that the spray penetration for biodiesel was shorter than that for gas oil. Thus the air-fuel mixing process was relatively poor for the biodiesel fuel. Substantial fuel-rich mixture was formed at the centre of the combustion chamber, and a portion of this mixture that failed to burn was emitted as SOF. It was found that both the SOF level and the ignition delay increase with a decrease in the fraction of methyl oleate ester in biodiesel fuel.
A study of low-comression-ratio dimethyl ether diesel engines
Authors: Kajitani S , Chen Z , Oguma M , Konno M
Published: October 2002

A new concept of using dimethyl ether (DME) as an alternative fuel in direct injection compression ignition engines with low compression ratios was presented to seek a combustion regime with the highest thermal efficiency. The concept was experimentally evaluated by a comparison of performance and emissions between a DME-fuelled engine and the corresponding conventional diesel engine. The result demonstrated that the DME-fuelled engine is superior to the conventional diesel engine in terms of thermal efficiency, emissions and engine noise, particularly at low compression ratios. However, NOx emission is unacceptably high and needs to be reduced by exhaust gas recirculation (EGR) or after-treatment systems.
Dynamic simulation of a high-performance sequentially turbocharged marine diesel engine
Authors: Benvenuto G , Campora U
Published: October 2002

The sequential turbocharging technique is used to improve the performance of highly rated diese engines in particular at part loads. However, the transient behaviour of the sequential turbocharging connection/disconnection phases may be difficult to calibrate and requires an accurate study and development. This may be accomplished, in addition to the necessary experimentation, by means of dynamic simulation techniques.

In this paper a model for the dynamic simulation of a sequentially turbocharged diesel engine is presented. A two-zone, non-adiabatic, actual cycle approach is used for the chemical and thermodynamic phenomena simulation in the cylinder. Fluid mass and energy accumulation in the engine volumes are evaluated by means of a filling and emptying method. The simulation of the turbocharger dynamics combines the use of the compressor and turbine maps with a model of the sequential turbocharging connection/disconnection valves and of their governor system.

The procedure is applied to the simulation of the Wärtsilä 18V 26X engine, a highly rated, recently developed, sequentially turbocharged marine diesel engine, whose experimental results are used for the steady state and transient validation of the simulation code with particular reference to the sequential turbocharging connection/disconnection phases. The presented results show the time histories of some important variables during typical engine load variations.
Mixed-flow turbines for automotive turbochargers: Steady and unsteady performance
Authors: Karamanis N , Martinez-Botas R. F.
Published: October 2002

Turbochargers are finding increasing application to automotive diesel engines as cost effective means for improving their power output and efficiency, and reducing exhaust emissions; these requirements have led to the need for highly loaded turbocharger turbines. A mixed-flow turbine is capable of achieving its peak isen-tropic efficiency at reduced velocity ratios compared to a typical radial inflow turbine; it is therefore possible to improve the turbocharger/engine matching. These turbines differ from the commonly used radial turbines in that the flow approaches the rotor in the non-radial direction; in the extreme a mixed-flow turbine would become an axial machine. The steady and unsteady performances of a mixed-flow turbocharger turbine with a constant blade inlet angle have been investigated. The steady flow results indicated that the mixed-flow turbine obtains a peak efficiency (total-to-static) of 75 per cent at a velocity ratio of 0.61, compared with that of a typical radial-inflow turbine which peaks at a velocity ratio of 0.7. The performance and flow characteristics were found to deviate significantly from the equivalent steady state values commonly used in turbocharger turbine design.
Performance and heat release analysis of a pilot-ignited natural gas engine
Authors: Krishnan S. R. , Biruduganti M , Mo Y , Bell S. R. , Midkiff K. C.
Published: October 2002

The influence of engine operating variables on the performance, emissions and heat release in a compression ignition engine operating in normal diesel and dual-fuel modes (with natural gas fuelling) was investigated. Substantial reductions in NOx emissions were obtained with dual-fuel engine operation. There was a corresponding increase in unburned hydrocarbon emissions as the substitution of natural gas was increased. Brake specific energy consumption decreased with natural gas substitution at high loads but increased at low loads. Experimental results at fixed pilot injection timing have also established the importance of intake manifold pressure and temperature in improving dual-fuel performance and emissions at part load.
Litigation Costs and Returns to Experience
Authors: Oyer Paul , Schaefer Scott
Published: October 2002

We develop a model linking maximum damage awards available to plaintiffs in wrongful termination lawsuits, workers' propensity to sue as a function of experience, and returns to experience. Using Equal Employment Opportunity Commission data on protected-worker discrimination complaints and labor-market data from the Current Population Survey, we examine how returns to experience among protected workers changed around the passage of the Civil Rights Act of 1991. We show that employers' reactions to employment protections may induce redistributive effects. Furthermore, these effects operate not merely across groups of differing protected status, but also within groups of identical protected status.
Racial Integration as an Innovation: Empirical Evidence from Sports Leagues
Authors: Goff Brian L , McCormick Robert E , Tollison Robert D
Published: October 2002

This paper treats racial integration as an innovation in economic process in which economic entities find it advantageous to utilize potentially more productive inputs previously unavailable due to law, custom, or managerial discretion. Data on the racial integration of Major League Baseball and Atlantic Coast Conference basketball are employed to address this issue. The central question examined is which type of team integrated first—losers or winners? The results strongly support the idea that entrepreneurship trumps competitive rivalry; that is, winning teams led the process of racial integration.
Increasing Returns and All That: A View from Trade
Authors: Antweiler Werner , Trefler Daniel
Published: October 2002

Do scale economies help to explain international trade flows? Using a large database on output, trade flows, and factor endowments, we find that allowing for the presence of increasing returns to scale in production significantly increases our ability to predict international trade flows. In particular, using trade data, we find that a third of all goods-producing industries are characterized by increasing returns to scale. Thus, scale economies are a quantifiable and important source of comparative advantage.
How Important Is Human Capital for Development? Evidence from Immigrant Earnings
Authors: Hendricks Lutz
Published: October 2002

This paper offers new evidence on the sources of cross-country income differences. It exploits the idea that observing immigrant workers from different countries in the same labor market provides an opportunity to estimate their human-capital endowments. These estimates suggest that human and physical capital account for only a fraction of cross-country income differences. For countries below 40 percent of U.S. output per worker, less than half of the output gap relative to the United States is attributed to human and physical capital.
States and Power in Africa by Jeffrey I. Herbst: A Review Essay
Authors: Robinson James A
Published: October 2002

Herbst argues that Africa is plagued by “state failure” to provide certain public goods in society, such as law and order, defense, contract enforcement, and infrastructure. Herbst has provided a bold, historically informed theoretical analysis, essential reading for economists interested in comparative institutions and development.
Looking Inside the Labor Market: A Review Article
Authors: Howitt Peter
Published: October 2002

When unemployed workers are available, why don't firms cut wages until the excess supply is eliminated? In his book, Why Wages Don't Fall During a Recession, Truman F. Bewley concludes, based on interviews with managers and labor leaders, that the most important factor inhibiting wage cuts is the psychological factor of morale. Bewley's field research has made an outstanding contribution to our knowledge of labor markets, by providing a close-up view of exactly what happens from the vantage point of the participants.
Evolution of Social Behavior: Individual and Group Selection
Authors: Bergstrom Theodore C
Published: October 2002

How selfish does our evolutionary history suggest that humans will be? We explore models in which groups are formed and dissolved and where reproduction of individuals is determined by their payoffs in a game played within groups. If groups are formed “randomly ” and reproductive success of group founders is determined by a multiperson prisoners' dilemma game, then selfish behavior will prevail over maximization of group payoffs. However, interesting models exist in which “group selection ”sustains cooperative behavior. Forces that support cooperative behavior include assortative matching in groups, group longevity and punishment-based group norms.
A Statistical Approach for Additional Infill Development
Authors: Jobe J. Marcus , Jobe Hutch
Published: October 2002

Ultimate recovery data are frequently modeled as being lognormal without consideration of other possible distributions. A typical approach is to use lognormal probability paper and a mean value (Swanson's mean) is calculated as well as chance factors. Engineers have identified a competing probability model for lifetime data called the Weibull distribution. In this paper, we consider the Weibull distribution as a potential alternative probability model for ultimate recovery data. Optimal methodologies of estimating the mean ultimate recovery for both the lognormal and the Weibull distributions are presented. Statisticians refer to this optimal approach as maximum likelihood methodology. Further, probability plots and hypothesis testing methods are presented that help reveal whether one should use the Weibull model or the lognormal model for available ultimate recovery data. Finally, a simulation approach is proposed to predict the average ultimate recovery value for “n” additional wells. An example with real data concludes the paper.
Estimates of Worldwide Gas Hydrate Resources
Authors: Lerche I.
Published: October 2002

Gas hydrates have been touted as the next generation of energy resources exploitable for commercial gain and anthropogenic use. It would then seem relevant to estimate the potential resources available in order that one has an appreciation of availability. Several such estimates have been made over the years for both onshore and offshore gas hydrates. This paper examines the relative percentages and the ranges of uncertainty for both the onshore and offshore estimates. In addition, the estimated resources are plotted versus the year in which the estimate was made to see if any convergence of results is being achieved with time as more data become available.

The main conclusions are that there seems not to be any systematic pattern of convergence of resource estimates with time, nor does there seem to be any narrowing of the uncertainty of the estimates for either onshore or offshore resource estimates as more data have become available over the last twenty years. It would seem that a concerted effort is needed to improve estimates if there is to be any hope of assessing the commercial worth of hydrate resources and of deciding whether hydrates really do represent a significant exploitable energy resource on a worldwide basis.
A Note on Optimization of Deviated Well Drilling Angles
Authors: Lerche Ian
Published: October 2002

A simple illustration is employed to show that the optimal angle one should use to drill an exploration well is dependent on two major factors: (i) the depth distribution anticipated for hydrocarbon-beating reservoirs in a particular exploration setting; (ii) whether the borelength, L, approved for drilling is long enough to more than encompass the depth, H, at which the anticipated reservoir distribution reaches its average value. If both conditions are estimated to be satisfied, then one should drill a deviated hole at an angle θ with respect to the vertical given by cosθ =H/L. This angle minimizes the probability that one will not encounter a hydrocarbon-bearing reservoir. If the second condition is not expected to be satisfied, then a vertical borehole represents the best chance of minimizing the probability of not encountering a reservoir. Using the general procedure illustrated here, historical databases in analogous geological settings can be used to sharpen the estimate of optimized drilling angle.
Economic Assessment of Multiple Reservoirs in Oil Field Development
Authors: Lerche I.
Published: October 2002

Many individual oil fields have multiple producing horizons. A question of some interest in developing an oil field is when does it make sense to drill for further horizons, based on the knowledge one has already obtained from the known horizons. Such an assessment must incorporate the economic chances of successfully finding another horizon and also the likely gains and costs involved. This paper shows how that question can be answered using Bayesian up-dating methods for improving success probabilities based on the information of known producing horizons, and incorporating both uncorrelated and correlated reservoir information to improve the chances of success. A case history is provided to illustrate how this objective procedure operates in practice.
Sidetrack and Recompletion Risks in Oil Fields. I. Recompletion Decisions Based on Estimated Net Present Value
Authors: Lerche I. , Noeth S.
Published: October 2002

This paper develops a procedure for assessing quantitatively the economic risk associated with deciding whether to undertake a recompletion job for an undeveloped oil-bearing horizon in a producing oil field. Decisions to proceed, or not, with the recompletion depend upon the estimated probability of a successful recompletion and on the estimated probability one will kill the producing horizon in the process. Also of concern are the estimates of total residual production for the producing horizon, the estimates of potentially recoverable reserves in the untapped horizon, together with associated recompletion costs, production costs per barrel, and selling price of product. Because one does not know ahead of performing the recompletion what the chances are of success and kill, then expected values and their uncertainties (as measured by the volatility of the expected value), together with cumulative probabilities of the recompletion worth exceeding the worth without recompletion, and also the expected worth required in order to satisfy a corporate declared mandate of a minimum acceptable chance of improved worth, are all used to provide risk measures to the corporate decision-makers.

Several numerical examples are provided to illustrate how one can rapidly evaluate such risky situations in terms of present-day worth values. Considerations of uncertain ranges of parameters involved in the risk assessment, and of models for future inflation rates, selling price time-dependence, and production variations (so that one can provide an assessment of when a recompletion job should be undertaken) are considered in later papers in this series.
Unstable Passive Continental Margins are Currently Unacceptable Candidates for Detailed Risk Analysis
Authors: Lowrie Allen , McGee T. M. , Jenkins Linda
Published: October 2002

Hydrates are near-surface phenomena that occur when temperatures and pressures are appropriate. Among such stable continental margins is the East Coast of the United States that, with its ubiquitous, leisurely, uniform deposition and relatively minor deformation, there can be associated hydrates. The geologic uniformity and long-term stability provide opportunities for stress homogenization with few perturbations, creating zones of weakness. With widely spaced sampling adequate to define a regional model, uncertainty can be reasonably calculated. Along unstable continental margins such as the northern Gulf of Mexico that contain such dynamic elements as salt and/or shale, as well as highly variable and massive deposition rates, there can be deformed stress fields that result from compression, lateral motions and variations thereof. Locally, any stress may be principal for an indeterminate time. With such variability, no detailed regional model can be developed. Risk analysis is possible only when a 3D model at sufficient resolution is available so that reasonable integrations can be performed and posed questions can be answered. To derive such a 3D model requires that all impacting processes, their intensities and periodicities, and spatial distributions be catalogued and understood. Thus, the “final” 3D model will be of variable resolution. To know at what resolution data need to be collected will be determined by the specific processes being mapped in a given locality. To apply an equitable risk analysis along unstable passive continental margins could be premature, given the uncertainty of all the operative processes. A conceptually valid 3D model of processes is not available, nor is an understanding of intensities and periodicities. Synergistic relationships can only be guessed. The principles of risk analysis are formulated; data and methodologies for use on unstable margins are not.
Uncertainties and Sensitivity Analysis of Thermal Parameters: Pseudo-Inversion Applied to 1D Forward Deterministic Models
Authors: Thomsen René Orla , Noeth Sheila
Published: October 2002

In petroleum studies quantitative tools such as basin modelling are widely used when ranking exploration targets and assessing associated geologic risk. It is therefore vital to assess the confidence that can be associated with the results of a given model based on available measured (control) data. Model validity is checked by an often time consuming (trial and error) calibration against measured data attempting complicated modifications of the model to satisfy the highly non-linear relationships between model parameters. These procedures often result in over-stated confidence in model results. Inversion procedures, however, aim at finding the simplest constellation of model parameters that best agree with calibration data taking the known uncertainties into account. A rapid pseudo-inverse method is presented for 1D deterministic forward models. A simple model for parameter behaviour is used to map the “real” behaviour into the simple model space. Then, by approximating the residual surface with a polynomial or cubic spline interpolation for a few data points only, the resolution limits, sensitivity and uncertainty can be easily assessed and the residual surface can be converted to a pseudo-probability density function for use in later risking procedures. From a measure of the goodness of fit to observed data, in this case vitrinite reflectance, the significance of variations of different input parameters, in this case heat flow, can be rapidly evaluated and uncertainties assessed. The method is illustrated on a data set from a detailed 1D modelling study of a small region of the German Variscan Rhenish Massif.
Sidetrack and Recompletion Risks in Oil Fields IV. Recompletion Decisions and Effects of Uncertain Parameter Values and Distribution Choices
Authors: Lerche I. , Noeth S.
Published: October 2002

This paper describes a procedure for the assessment of risks and uncertainties for the problem of deciding whether to do a recompletion job in an undeveloped oil-bearing horizon in a producing oil field. The model used for calculating estimated recompletion worth incorporates a set of parameters, such as the estimated gains and costs of both the producing and the recompletion horizons as well as the chances of killing the producing well or of doing a successful recompletion. However, these parameters are themselves uncertain and therefore contribute to the uncertainty in the estimates of recompletion worth. A probabilistic approach to this problem, using Monte Carlo simulation techniques, is used here. The method quantifies three different types of uncertainties that contribute in different proportions to a total uncertainty related to the recompletion worth. These types are: the uncertainty related to probability that the path outcome is successful (path uncertainty); the uncertainty arising from value ranges for each parameter (parameter uncertainty); and uncertainty that influences recompletion worth by allowing different distribution types to be used from which are drawn the various ranges of the input parameters (distribution uncertainty). The evaluation of the different relative contributions (%RC) of these three components to recompletion worth enables one to determine precisely where to focus efforts to improve accuracy of recompletion worth and so to decrease risk. This enablement is done by focusing on the relative sensitivity of the parameters contributing to the different types of uncertainties and optimizing these coherently. Several numerical illustrations are given to illustrate how one can rapidly evaluate the different uncertainties in a system in terms of present-day worth.
Sidetrack and Recompletion Risks in Oil Fields. VI. Decisions to Abandon Based on Further Data Collection
Authors: Lerche I. , Noeth S.
Published: October 2002

Based upon the premise that an accurately targeted decision to proceed or not with a recompletion or sidetrack job in an oil field may not be possible without further information, this paper investigates what worth is brought to resolving such decision uncertainty by acquiring new data, and relates the cost of such data to changes the data bring about in the worth of going ahead with a development job. Limitations to the costs of such data, and of undertaking further studies should the acquired data not resolve the situation, are examined in relation to the estimated worth of the development project and also to the probability that a successful profitable outcome for the development project will prevail. Given the uncertainties on such future estimates, an investigation is also given of the dominance of individual uncertain factors in contributing to the uncertainty of turning a profit. Five examples are given, designed to illuminate how the costs and uncertainties influence, sometimes very seriously, prior estimates of likely worth of the development project. Detailed considerations show which of the costs and uncertainties need to be lowered or better constrained if such a project is to be undertaken rather than abandoned because of the excessive costs involved that convert a very worthwhile project into one that can only lose even more money for a corporation.
Ergonomics & Vibration in Powered Hand Tools Used in Meat Processing
Authors: Johnson John E. , Wasserman Donald E.
Published: October 2002

The purpose of this study was to determine the triaxial acceleration levels of a group of powered circular knives extensively used in the meat processing industry. These tools were tested in real time under actual work conditions while the operators used the tools in 23 different applications. The length of the study was 11 months, encompassing 685 tools, at 13 plant sites using 5 different diameters of circular tools. All vibration tool measurements were recorded from three triaxially mounted individually calibrated, PCB accelerometers. Customized software programs allowed a Gateway 2000 SOLO computer to cycle, collect, and record vibration data for a minimum of a one minute time frame. The study results showed that neither the ANSI S3.34 nor the ACGIH hand-arm vibration standards were exceeded for an 8–hour workday. The median acceleration levels for the five different sized diameter tools did not significantly differ. The operating levels increased only slightly from a new tool that has been determined to be operating at maximum efficiency. Examining the different tool applications, operators, plant locations and tool conditions resulted in concluding that for this type of tool the most important factor contributing to the acceleration intensity levels was tool maintenance and the conditions of its parts. Tools with higher vibration acceleration levels were disassembled and found to have at least one part severely worn or damaged. After the part(s) were replaced, the tool was re-tested under the same work conditions, the vibration acceleration levels on average decreased by 16%. As part of an overall effort, operator exposure to vibration generated by these powered circular knives can be significantly reduced and controlled by proper tool care and maintenance.
Effect of Tunnel Diameter on Ground Vibrations Generated by Underground
Authors: Lin Trains Qinhua , Krylov Victor V.
Published: October 2002

A theoretical model has been developed of generating ground vibrations by underground trains travelling in idealised circular tunnels of finite diameter. By means of the reciprocity principle, the displacement field radiated by a point force applied to the bottom of the tunnel, i.e., the Green's function of the problem, has been derived in zero and first approximations versus tunnel diameter. This more precise Green's function has been applied to carry out calculations of railway-generated ground vibrations using earlier developed methods. The results show that the velocities of generated low-frequency ground vibrations increase with the increase in tunnel diameter. It is also shown that zero approximation is accurate only at very low frequencies.
Delamination Detection in Composite Laminates from Variations of Their Modal Characteristics
Authors: Valdes S.H. Diaz , Soutis C.
Published: October 2002

As a first step in developing a health monitoring system, the effect of delamination on the modal frequencies of laminated composite beams has been investigated. A piezoceramic patch driven with a linear rapid frequency sweep was used to induce vibrations on the structure and its response registered via piezoelectric sensors. Modal frequencies were obtained using concepts of resonant ultrasound spectroscopy (RUS). Changes of the modal frequencies after delamination initiation, compared to those of a non-delaminated specimen, gave a good indication of the degree of damage, demonstrating the feasibility of using measured changes in the vibration characteristics to detect damage.
Fulfilling the Hand-Arm Vibration Requirements of the EU Machinery Directive
Authors: Brereton Paul , Hewitt Sue
Published: October 2002

The Machinery Directive was written to facilitate the establishment of the single European market by harmonising Member States' health and safety requirements for machinery so eliminating barriers to trade. The Machinery Directive specifies a hierarchy for selection of methods to eliminate risk of accident or ill-health throughout the foreseeable lifetime of the machine. Designers of new machinery are obliged to:

eliminate or reduce risks as far as possible (inherently safe machinery design and construction); take the necessary protection measures in relation to risks that cannot be eliminated; and inform users of the residual risks due to any shortcomings of the protection measures adopted, indicate whether any particular training is required and specify any need to provide personal protection equipment.

The Health & Safety Executive (HSE) of the United Kingdom is investigating the hand-arm vibration risks of powered hand-tools and the value of vibration information supplied with the tools. Manufacturers appear to be successfully reducing the vibration emissions of many types of tool. There are many classes of tool that have a wide range in the vibration emissions – frequently up to 4:1 between the highest and lowest emissions in a class. The data provided by manufacturers is likely to provide broad guidance as to which tools are likely to produce the most and least vibration in normal use but often fails to provide an indication of risk.
Low Frequency Noise and Annoyance in Classroom
Authors: Lundquist Pär , Holmberg Kjell , Landström Ulf
Published: October 2002

The most common method for noise assessment is the A-weighted sound pressure level. The question has been raised as to whether the frequency weighting with an A-filter gives a correct result when assessing the annoyance response to noise containing strong low frequency noise (LFN) components. One method suggested to identify LFN is the dB(C) – dB(A) difference. The aims of this study are to investigate if background noise in Swedish elementary schools is to be considered as LFN, further to test the hypothesis that students exposed to audible LFN at high levels are more annoyed than students exposed to LFN at lower levels. The results indicate that the noise in 16 out of 22 classrooms should be considered as LFN. The analysis did not show any difference in rated annoyance between students exposed to high LFN levels and students exposed to low LFN levels.
A Study of the Effect of Floor Mobility on Isolation Efficiency of Vibration Isolators
Authors: Mak C. M. , Jianxin Su
Published: October 2002

Despite the benefits of HVAC equipment, this can produce structure-borne sound as well as air-borne sound. This sometimes causes vibration of the electrical and mechanical services (E&M) roof or floor that is high enough to make the spaces they serve unusable. Therefore, good acoustical design plays an important role in the design of HVAC systems. Although vibration isolators are usually employed to reduce the vibrational power transmitted from the machine to the E&M floor, the effect of floor mobility on the isolation efficiency is usually ignored by engineers. A great deal of vibrational energy can sometimes be transmitted to the E&M floor and emitted as noise to the room below. The aim of this paper is therefore to clarify the effect of floor mobility on the isolation efficiency of vibration isolators for HVAC equipment.
The Changes and Significance of TXA2 and PGI2 Metabolism after Rat Infrasonic Brain Damage
Authors: Fei Zhou , Zhang Xiang , Li Zhi-Gang , Liu En-Yu , Bai Hong-Min , Chen Jing-Zao , Jia Ke-Yong
Published: October 2002

In this paper we study the changes and significance of the TXA2 and PGI2 metabolism after infrasonic damage to rats so as to probe the mechanism of infrasonic biological effects. Some 40 SD rats were randomized into control, infrasonic damage once, 7 times, 14 times, and treatment five groups. A stimulus of 8Hz 120dB infrasound was applied to the infrasonic damage groups for 2 hours once according to the planned times. Radioimmunoassay was used for the examination of brain TXB2 and 6-keto-PGF1a (metabolites of TSA2 and PGI2) contents. The results showed that there were no changes in TXB2 and 6-keto-PGF1a levels in the ‘once’ group while TXB2 level elevated significantly and 6-keto-PGF1a level decreased remarkably in the 7 times and the 4 times groups with an augmentation of TXA2/PGI2 value. In the treatment group both TXB2 and PGI2 levels nearly reached normal. It is concluded that the augmentation of the TXA2/PGI2 value in the 7 times and 14 times groups suggests that an imbalance in TXA2-PGI2 production contributes to the traumatic secondary processes, which include ischemia and edema. Also, the extent of TXA2 and PGI2 metabolism disturbance is closely related to the times of infrasonic injury. It is hypothesized that mGluR antagonist may exert its protective properties through increasing PGI2 production in the injured brain by improving the blood supply to injured blood vessels.
Danish Guidelines on Environmental Low Frequency Noise, Infrasound and Vibration
Authors: Jakobsen Jorgen
Published: October 2002

In Denmark a set of guidelines for measurement and assessment of environmental low frequency noise, infrasound and vibration was published in 1997 as “Information from the Danish Environmental Protection Agency no. 9/1997” (Miljøstyrelsen2). Recommended measurement methods are specified, and recommended limit values for noise and vibration are given. In this paper a brief description of the measurement methods is given, the recommended limit values are shown, and the background for the measurement and assessment methods is discussed. This paper is an extended summary of “Information from the Danish Environmental Protection Agency No.9/1997” (in Danish)
NDT of Piled Foundations: Data Processing with Artificial Neural Networks
Authors: Watson J. N. , Fairfield C. A. , Wan C. L.
Published: October 2002

The low strain test method is the prevalent method for integrity testing of cast in situ foundation piles. The automated interpretation of sonic echo traces from this test may prove beneficial to industry through standardisation of the test method and a reduction in the time spent analysing data. In this research the generalisation and feature extraction strengths of artificial neural networks have been exploited for test data interpretation. This study involved the use of a multilayer perceptron network considered most suitable for this heteroassociative function approximation task. The network was trained using numerically generated data. Field data from two sites confirmed that the network identified, located and quantified changes in pile diameter as well as detecting pile lengths to within 5% of their design values.