bluuebunny/crossref_metadata_2025 huggingface dataset:
Are There Commercial Deposits of Methane Hydrates in Ocean Sediments?
Authors: Hovland Martin
Published: October 2002

Naturally occurring gas hydrates forming in the ocean floor sediments have, ever since the 1970s, been heralded as the next century's viable energy source. Is this really so? What has the Ocean Drilling Program (ODP) found out about the nature of the Bottom Simulating Reflector (BSR) as an indicator of large volumes of gas hydrates and free natural gas? The findings so far from ODP's legs 146 and 164 have been rather discouraging with respect to the in situ amounts of both gas hydrates and free gas. In the sediments drilled on Leg 146, on the Cascadia accretionary wedge off Oregon, USA, the average amount of gas hydrates above a prominent BSR was estimated at 1 – 2 percent by sediment volume. The free gas amount below the BSR was 3–4 percent by sediment volume. On Leg 164 in the Western Atlantic Ocean (Blake Plateau) some higher amounts, averaging up to 4 – 6 percent and 5 – 7 percent by volume of sediment, respectively, were found. However, on the Hydrate Ridge, off Oregon (Cascadia, just south of Leg 146), there has recently been discovered apparently large amounts of sediment-mixed gas hydrates, which may be exploitable.

Although the general percentages found so far are much too low for commercial extraction (even a high-grade copper-ore on land must average more than 6 percent by volume), there may exist some high-grade regions worth exploring. But, the question remains: Where shall we seek the high-grade gas hydrate deposits in ocean sediments? Besides the obvious deep-water high porosity conventional type of reservoirs, and judging from recent findings in the Gulf of Mexico and the Caspian Sea, perhaps the most promising locations are those where mud volcanoes occur on the ocean floor.
Sidetrack and Recompletion Risks in Oil Fields. III. Recompletion and Production Modeling with Time
Authors: Lerche I. , Noeth S.
Published: October 2002

The inclusion of models of production of oil with time and of selling price, costs and their temporal variations, all influence the timing decision of when to undertake a recompletion to another horizon relative to potential residual gains from a currently producing horizon. In this paper we show how models of such effects can be incorporated into the evaluation of whether, and when to undertake recompletion. Three simple numerical illustrations are given to demonstrate the influence of different choices of production models on the assessment of the best time to undertake a recompletion job.
The Changes of Rat Blood-Brain Barrier Permeability and Expression of Heat Shock Protein 70 after Infrasonic Damage
Authors: Fei Zhou , Zhang Xiang , Wang Xiao-Feng , Li Zhi-Gang , Lu Pei-Ling , Liu Xian-Zhen , Chen Jing-Zao , Jia Ke-Yong
Published: October 2002

To study the changes of blood-brain barrier (BBB) permeability and the heat shock protein 70(HSP70) after infrasonic damage, 40 SD rats were randomized into control, infrasonic damage 1 time, 7 times and 14 times groups. 8Hz 120dB Infrasound of 8Hz frequency and 120dB level was applied to the infrasonic damage groups for 2 hours once according to the planned schedule. The right frontal cortex was sampled for immunohistological examination. Under the electronic microscope changes of cerebral ultrastructure and BBB permeability were observed. Results showed that with the increase in the times of infrasonic damage, cerebral ultrastructure became more aggravated. The 1 and 7 times group shared the same changes of BBB permeability in which tight conjunction opened and Lanthanum nitrate particles passed BBB into the brain tissue. Moreover, the 14 times group has more radical changes in which a great deal of Lanthanum nitrate particles exist in the brain tissue (P<0.05). While, in 1 time group there is a weak positive HSP70 neuronal expression, the 7 and 14 times groups shared the same changes of strong HSP70 neuronal expression. It is concluded that infrasound can directly damage the function and structure of cerebral ultrastructure and BBB, and in the same degree, the extent of brain damage and positive HSP70 neuronal expression is closely related to the times of infrasonic injury. It is suggested that infrasound plays a pivotal role in brain damage which can in turn limit the expression of HSP70 through increasing BBB permeability.
The Deelen Infrasound Array for Recording Sonic Booms and Events of CTBT Interest
Authors: Evers L. G. , de Bree H-E , Haak H. W. , Koers A. A.
Published: October 2002

The Seismology Division of the Royal Netherlands Meteorological Institute (KNMI) has built up expertise in infrasound measurements by investigating low frequency events in order to distinguish between seismic and sonic events. KNMI operates, amongst others, a sixteen element microbarometer array with an aperture of 1.5 km, the Deelen Infrasound Array (DIA). Sonic booms and events of Comprehensive Test Ban Treaty (CTBT) interest are detected and identified within the frequency range of 500 seconds up to 40 Hertz. Recently, KNMI and Microflown Technologies B.V. started a collaboration concerning infrasound measurements. This paper reports on the use of a novel sensor. The so-called Microflown[1] is a micro-machined particle velocity sensor, sensitive to frequencies from 0Hz up to at least 1kHz. Experiments with the Microflown for infrasound detection show promising results.
Proposal of New Limit Values for Occupational Exposure to Infrasonic Noise in Poland
Authors: Pawlaczyk-łuszczyńska Małgorzata , Kaczmarska-Kozłowska Anna , Augustyńska Danuta , Kameduła Maria
Published: October 2002

Proposals for new Polish limits for occupational exposure to infrasonic noise were put forward based on a comprehensive analysis of literature data concerning the effects of infrasound on humans, the existing standards and occupational exposure limits, and results of our own infrasonic noise measurements. It is suggested that according to the health-based criteria an equivalent continuous G-weighted sound pressure level normalised to a nominal 8–hour working day or 40–hour working week should not exceed 102 dB. Additionally, an overall unweighted peak sound pressure level should not be higher than 145 dB.
Dynamic Modelling of a Flexible Manipulator System Incorporating Payload: Theory and Experiments
Authors: Tokhi M. O. , Mohamed Z. , Shaheed M. H.
Published: October 2002

This paper presents theoretical and experimental investigations into the dynamic characterisation of a flexible manipulator system. A constrained planar single-link flexible manipulator is considered. A dynamic model of the system, incorporating structural damping, hub inertia and payload, is developed using finite element methods. Effects of damping and payload on the response of the flexible manipulator are discussed. Performance of the algorithm in describing the dynamic behaviour of the system is assessed in comparison to an experimental test-rig. Experimental results are presented for validation of the developed finite element model in the time and frequency domains.
Dynamic Analysis of Delayed Damper System in Engineering Structures
Authors: Dingyue Chen , Hui Xu , Jianjia Dong
Published: October 2002

The delayed damper (DD) is a new active vibration absorption technique which uses time-delayed partial state feedback to generate ideal resonance on a passive vibration absorber. It has many attractive features such as real-time tunability, ease of implementation, and total suppression of vibration for tonal frequency disturbances. In this paper, a major advantage of engineering structures analysis is the reduction of characteristic roots from infinite numbers to finite numbers and consequent simplicity in the dynamic analysis of the controller. The dynamic model principle is employed to design controllers for the structure. The system is examined by simulation. It is shown that engineering structures control application for DD yields better vibration suppression considering the sampled control structure in implementations.
Measure and Study of Precursory Infrasonic Waves of Strong Earthquakes in May 2000
Authors: Su Fang , Tian Wei
Published: October 2002

The infrasonic signals (the P-t curve, the direction and horizontal velocity of the wave and the three-dimensional dynamic frequency spectrum) stimulated by seven strong earthquakes in May 2000 were introduced. The results over a year are as follows: (1) 10 days or so before the occurrence of a strong earthquake, the precursory infrasound of the earthquake with strong amplitude and measurable direction can often be observed. The characteristics of the spectrum are: the amplitudes of precursory infrasound increase from weak (10–20Pa) to strong (40–80Pa) or even stronger; the final periods become very wide (2–65min); their waveforms are distinctly different from those of meteor showers and strong winds, (2) The maximal amplitude of the precursory infrasound measured is related not only to the magnitude of earthquake, but also to the distance and the depth of the epicentre and some other factors. (3) The generating and propagating mechanism of the precursory infrasound of the earthquake was preliminarily explained. (4) If the directions of two tripartite arrays intersect, the location of the epicentre can be predicted. Therefore measurements of precursory infrasound could become a new and more effective method of the imminent prediction of strong earthquakes.
Manufacture and Characterisation of Silicalite Monoliths
Authors: Lee L.Y. , Perera S.P. , Crittenden B.D. , Kolaczkowski S.T.
Published: October 2002

Multichannel monoliths containing up to 90% silicalite by weight and with cell densities up to 28 cells/cm2, wall thicknesses down to 0.6 mm and an overall diameter of 40 mm have been prepared from silicalite powder and sodium bentonite (as a binder) by the unit operations of paste preparation, extrusion, drying and firing. The manufactured monoliths, which show good strength, retain the crystal structure and micropore size of the source silicalite powder, and adsorption measurements made by using a dynamic flow system confirm that the monoliths exhibit an equilibrium performance broadly similar to that of commercial silicalite pellets. In addition, the manufactured monoliths possess a higher macroporosity than the commercial pellets. Regeneration of the monoliths was found to be possible at mildly increased temperature. These features augur well for the recovery and/or separation of organic compounds in simple pressure swing and thermal swing processes.
Synthesis, Characterization and Application of a Derivatized Acidic Salt of a Tetravalent Metal. Pyridine Anchored on to Tin(IV) Tungstoselenate
Authors: Nabi S.A. , Islam A. , Rahman N.
Published: October 2002

The inorgano-organic ion-exchanger, tin(IV) tungstoselenate–pyridine, has been prepared by derivatizing the inorganic ion-exchange material, tin(IV) tungstoselenate, with an organic moiety, pyridine. Chemical studies showed the tin(IV) tungstoselenate/pyridine mole ratio to be 806.5:1, indicating a weak sorption of pyridine on to the surface of the tin(IV) tungstoselenate. The material was characterized on the basis of SEM, FT-IR, TGA and DTA studies. The uptake of Cu2+, Ni2+, Fe2+ and Fe3+ ions was found to be much higher on tin(IV) tungstoselenate–pyridine relative to tin(IV) tungstoselenate. The uptake of these metal ions as a function of loading and pH was also studied when the following affinity order was observed: Cu2+ > Co2+ > Ni2+ > Fe2+ > Fe3+. The uptake of metal ions increased initially with loading but became constant at higher loading. The most favourable pH range was found to be that between 3.5 and 4.5.
The Structure and Catalytic Activity of Pt Complexes Heterogenized on a Silica Surface
Authors: Yatsimirsky Vitaly K. , Belyakova Lyudmila A. , Oleksenko Lyudmila P. , Boldyreva Ol'ga Yu.
Published: October 2002

The catalytic activity of complex compounds containing different metal contents immobilized on a silica surface towards the oxidation of carbon monoxide and hydrogen has been investigated. In addition, the influence of the concentration of hydrogen and oxygen and the treatment of such catalysts by the individual components in the reaction mixture on their catalytic activity in the hydrogen oxidation reaction has also been studied. The structural peculiarities of platinum complexes heterogenized on a silica surface have been established by diffuse reflectance electronic spectroscopy.
Surface Characteristics and Catalytic Oxidation of CO on Silicalites and Silicalites Containing Cobalt, Copper and Silver Oxides
Authors: Mohamed Farid Sh.
Published: October 2002

Two silicalite samples, S1 and S2, were prepared hydrothermally in the presence of tetrapropylammonium bromide (TPA–Br) and tetrabutylammonium bromide (TBA–Br), respectively. Cobalt oxide, copper oxide or silver oxide (all at 10 wt% concentration) were incorporated into the S1 and S2 silicalites by impregnation methods. The structural and textural properties of the prepared samples were studied using a variety of techniques together with their ability to catalyze the oxidation of CO. The results obtained indicated that S1 and S2 existed as pure phases with structures analogous to those of ZSM-5 and ZSM-11 zeolites, respectively. Electron microscopic analysis showed that the crystalline morphology of S1 and S2 consisted of intergrown discs and shelf-like shapes with diameters in the range 10–15 μm and 29–33 μm, respectively. Differences noted during kinetic studies of CO oxidation over the prepared samples were discussed.
Study of the Adsorption Mechanism and the Structure of Adsorbed Layers of Polyelectrolytes at the Metal Oxide/Solution Interface
Authors: Chibowski S. , Wiśniewska M.
Published: October 2002

The influence of the molecular weight of polyacrylic acid (PAA) and polyacrylamide (PAM) as well as of inorganic contaminants on the ZrO2 surface on the adsorption and electrokinetic properties of the metal oxide/polyelectrolyte solution interface were studied for ZrO2 and Fe2O3 solid particles.

The calculated concentrations of the various surface groups on ZrO2 and Fe2O3 enabled an investigation of the possible mechanism for the bonding of the studied polyelectrolytes with the surfaces of both oxides. PAA and PAM macromolecules bond with the solid surface mainly via the –OH groups of the oxides, which may interact with the carboxy groups of polyelectrolytes through hydrogen bridging.

A comparison of the change in values of the diffuse layer charge with the surface charge enabled the principal factors responsible for the changes in the zeta potential of the oxides, e.g. pH, polymer molecular weight and concentration of the polymer solutions, to be evaluated. From such zeta potential values, it was possible to determine the free energies of adsorption of PAA and PAM on the surfaces of both oxides.

The thicknesses of adsorbed polymer layers on Fe2O3 and ZrO2 were calculated on the basis of measurements of their suspension viscosities in the absence and presence of adsorbed polymer. It was shown that the thickness of the adsorption layer increased with increasing polymer molecular weight, pH and concentration of the polymer solution.

Because the experimental determination of the number and the length of trains, loops and tails in such polyelectrolytes was not possible, the participation of such segments of polymer structure at the interface was computed using the Scheutjens–Fleer model of polymer adsorption. The polymer adsorption expressed as the number of equivalent monolayers was calculated and compared with the experimental data.
Adsorption of Lead(II) Ions on Transcarpathian Clinoptilolite
Authors: Gomonaj V.I. , Golub N.P. , Szekeresh K. Yu. , Gomonaj P.V. , Charmas B. , Leboda R.
Published: October 2002

The adsorption of lead(II) ions on the natural forms of Transcarpathian zeolite under static and dynamic conditions was investigated. Partial conversion of inactive calcium ions in the zeolite into relatively more mobile sodium or ammonium ions resulted in an increase in the adsorption of Pb2+ ions. Similarly, partial removal of aluminium oxide from the zeolite changed its physicochemical properties and led to the maximum adsorption of lead(II) ions.
Modified Silica for the Extraction of Cadmium(II), Copper (II) and Zinc(II) Ions from Their Aqueous Solutions
Authors: Khalil L.B. , Attia Amina A. , El-Nabarawy Th.
Published: October 2002

Increasing concentrations of heavy metal ions in aquatic systems have led to a search for very efficient matrices for their removal. Zirconium(IV) phosphate has been used for many years as a cation-exchanger and dispersion of this phosphate on a high surface area silica might be expected to improve the extraction properties of the material.

Modified silica matrices (SiZrP) were prepared by refluxing high surface area silica with zirconium tetrachloride dissolved in ethanol, followed by stirring the dried product in an appropriate volume of 0.1 M H3PO4. The dried SiZrP samples thus obtained were used to extract Cd2+, Cu2+ and Zn2+ ions from their aqueous solutions under varying conditions.

The most efficient SiZrP sample was obtained when ZrCl4 was allowed to react with the silica in a 1:1 ratio. High extraction of all the ions studied at an initial concentration of 150 ppm was achieved over the pH range 3.5–6.0, with the order of metal ion extraction being Cd2+ > Cu2+ > Zn2+.
The Separation Enhanced Reaction Process (SERP) in the Production of Hydrogen from Methane Steam Reforming
Authors: Zou Yong , Rodrigues Alirio E.
Published: October 2002

This paper summarizes recent progress in the study of the separation enhanced reaction process (SERP) for the production of hydrogen from the steam reforming of methane (MSR) in a single unit operation. This process employs a packed column containing an admixture of a catalyst and an adsorbent or acceptor capable of selectively removing carbon dioxide as a reaction by-product from the reaction zone. The present status of research regarding various factors influencing the adsorbent and acceptor, respectively, are discussed in detail. The main advantages and disadvantages of SERP-MSR compared with the more conventional MSR process are advanced.
Adsorption of Biologically Active Compounds from Aqueous Solutions on to Commercial Unmodified Activated Carbons. Part III. Theoretical Description of Paracetamol Adsorption Data at Neutral pH
Authors: Terzyk Artur P.
Published: October 2002

A theoretical description of recently published paracetamol adsorption data on a series of non-modified commercial activated carbons is presented. Nineteen of the most widespread adsorption isotherm equations are analysed and the resulting maximum adsorption values compared. The equations proposed by Weber and Vliet, by O'Brien and Myers as well as by Dubinin and Astakhov led to the highest values of the average correlation coefficient describing the fit of the theoretical data to those obtained experimentally. On the basis of the results obtained as well as those published previously, the importance of carbon surface basic groups and carbonyl groups in the mechanism of paracetamol adsorption is emphasised.
Formex Configuration Processing I
Authors: Nooshin Hoshyar , Disney Peter
Published: October 2002

This is the first paper in a series of papers that are intended to cover the present state of knowledge in the field of formex configuration processing. This field of knowledge has been developed during the last three decades and has now reached a level of maturity that makes it an ideal medium for configuration processing in many disciplines. In particular, it provides a rich assortment of concepts that are of great value to the engineers and architects involved in the design of space structures.
Geometrically Nonlinear Analysis of Funicular Reticulated Domes
Authors: Rajasekaran S.
Published: October 2002

Contrary to the usual procedure, a desired state of stress is assumed and that corresponding funicular shells shape is obtained. The reticulated domes that are developed from these equivalent shells are called Funicular domes. For shallow shells the governing equation is a Poisson's equation and for deep shells the governing equation is a nonlinear partial differential equation. The Boundary Integral Element method is used to obtain the shape of the funicular reticulated domes. Nonlinear analysis is carried out to investigate the snap through buckling and load deformation response. Numerical examples are solved using the program “NLA” developed.
Kinematic Analysis of Deployable Scissor Structure s
Authors: Langbecker Travis
Published: October 2002

The paper deals with the geometric design of deployable scissor structures. These structures are classified as foldable or deployable. A foldable structure guarantees a stress free condition during deployment. A new equation, the foldability equation is derived. The foldability equation is formulated using a purely geometric approach. The foldability vector used in the foldability equation is formulated for some basic units in deployable structures. The foldability equation is then used to analyse the kinematics and determine the foldability/deployability of translational, cylindrical, and spherical configurations.
Design of Web Members in Space Trusses
Authors: El-Sheikh Ahmed
Published: October 2002

The work presented in this paper is intended to improve our understanding of how critical the web members are to the integrity of space trusses. The points covered include the internal force distribution in the web members both in the composite and non-composite states, and the implications on web member design. Also included is the effect of web member damage and geometric imperfections on overall space truss performance. Further, the consequences of slightly reducing the size of web members, which could be a viable option in some practical designs, are considered. Throughout the paper, the effects of different influences in web members are compared with the corresponding effects in chord members in order to relate the work done herein to earlier work found in the literature. The findings of this research could be of considerable importance to future practical space truss designs.
Computer Shape Finding of Form Structures
Authors: Meek John L. , Xia Xiaoyan
Published: October 2002

This paper presents a non-linear finite element procedure for shape finding of form structures and studies an approach wherein the engineer recognises formable curved surfaces focusing on the engineer's own imagination and creativity before turning to numerical analysis to assist in the design. With the investigation of a simple numerical method of locating geodesic lines, a convenient shape finding approach is presented. Another purpose of this paper is to present a method by which compression shell shapes can be obtained by inverting the loads on the tension shape obtained by loading a cable net system. This work parallels the physical models used by H. Isler for his work on thin concrete shells. The paper gives examples of the mesh shapes generated and the computer visualisation of several examples. It demonstrates that the computer modelling is a suitable alternative to the physical modelling process. The numerical results given show that the computer software is reliable, and provides the designer with a useful tool for membrane design.
Optimization of Large-Scale 3-D Trusses Using Evolution Strategies and Neural Networks
Authors: Papadrakakis Manolis , Lagaros Nikos D. , Tsompanakis Yiannis
Published: October 2002

The objective of this paper is to investigate the efficiency of optimization algorithms, based on evolution strategies, for the solution of large-scale structural optimization problems. Furthermore, the structural analysis phase is replaced by a neural network prediction for the computation of the necessary data for the evolution strategies (ES) optimization procedure. The use of neural networks (NN) was motivated by the time-consuming repeated analyses required by ES during the optimization process. A back propagation algorithm is implemented for training the NN using data derived from selected analyses. The trained NN is then used to predict, within an acceptable accuracy, the values of the objective and constraint functions. The proposed methodology has been applied in sizing structural optimization problems of large-scale three dimensional roof trusses. The numerical tests presented demonstrate the computational advantages of the proposed approach which become more pronounced for large-scale optimization problems.
Wind Energy Technology, Status Review
Authors: Milborrow David
Published: October 2002

Wind energy technology has developed extremely rapidly, and many commercial wind turbines now on the market have capacity ratings of one megawatt or more. Energy productivity per unit of rotor area has steadily improved. Turbine prices have decreased per unit capacity, so the cost of wind-generated electricity has fallen steadily. This paper examines design concepts, applications and economics, and looks to further developments, including offshore wind energy.
Simulation of the Wind Speed at Different Heights Using Artificial Neural Networks
Authors: Bechrakis D.A. , Sparis P.D.
Published: October 2002

In this paper, an estimation of the wind speed at different heights with artificial neural networks is presented. It is an alternative way to compute wind shear. This method was tested using pairs of data sets from two measuring stations, installed in different topographic locations. Wind speed simulation is performed with high accuracy. The calculation of the surface friction coefficient from the actual measurements is also compared for wind shear estimation with the typical method in terms of energy output. Results showed that artificial neural networks achieve a better wind speed simulation and wind power estimation at different heights, even in complex terrains.
Recent Advances in Small Wind Turbine Technology
Authors: Clausen P. D. , Wood D. H.
Published: October 2002

This paper reviews some recent advances in the technology of small wind turbines, whose upper power limit we take arbitrarily as 50 kW. Small turbines are used mainly for remote power generation either alone or in conjunction with other energy sources and battery storage. They can be divided into three categories: micro, up to 1 kW; mid-range; and mini-turbines, of 20 kW and larger, intended mainly for wind/diesel mini-grids. The paper discusses a number of issues that are category-dependent; for example, low-wind-speed performance is most critical for microturbines. The starting point for the review is the mature level of large wind turbine technology, and it is demonstrated that this maturity has yet to percolate downwards. Nevertheless, there have been a number of very encouraging recent developments. These include improvements to our understanding of the basic aerodynamics and advances in blade manufacturing, the use of micro-processor controls, and the increasing use of design certification and type approval. The developments are highlighted by two case studies of small turbine design in which the authors were involved. We conclude with a brief discussion of current developments in technology, such as fatigue testing of blades and new methods of blade design, which should further increase the level of small turbine technology towards that of large machines.
HAWT Aerodynamic Performance Prediction Using a Semi-Rigid Wake Model Based on Vortex Theory
Authors: Zhiquan Ye , Yan Chen , Feng Zhang
Published: October 2002

HAWT aerodynamic performance prediction is of great significance for wind turbine design and operation. A semi-rigid wake model based on the vortex theory is developed to analyze HAWT aerodynamic performance in this paper. The calculating methods for steady flow and unsteady flow are presented and the computer programs in FORTRAN language are compiled. The FD2.7-500 wind turbine rotor aerodynamic performance considering wind shear, cross-wind and tower shadow is calculated. The calculation results of the HAWT rotor performance using vortex theory and classic blade-element/momentum theory are individually compared with the experimental data. The comparisons show that the vortex theory gives more accurate performance than the classic blade-element/momentum theory does. When the tip-speed ratio is higher than 8, i.e. in the range of high tip-speed ratios, the power coefficients calculated by the vortex theory show agreement with the experimental data, but those calculated by the classic blade-element/momentum theory diverge from the experimental curve.
Modelling and Prevention of Ice Accretion on Wind Turbines
Authors: Makkonen Lasse , Laakso Timo , Marjaniemi Mauri , Finstad Karen J.
Published: October 2002

A numerical model that simulates ice accretion amounts and ice shapes on wind turbine blades is presented. The model simulates both rime icing due to fog droplets and glaze icing due to precipitation at all angles of droplet attack experienced by wind turbine blades. Icing can be simulated by the model also when the blade is heated. The sensitivity of ice accretions to meteorological variables is studied and predictions of the model are compared to data from icing wind tunnel experiments and from a field study of natural wind turbine icing. Applications of the model in the design of blade heating elements for anti-icing of wind turbines are described.
PWM Control Strategies for Wind Turbine Inverters
Authors: Wang Quincy , Chang Liuchen
Published: October 2002

This paper reviews the principles of three PWM control strategies, namely Harmonic Elimination, Current Hysteresis and Space Vector, which are used in the development of a 100kVA IGBT wind turbine inverter. Based on the simulations and the field test results, the comparison and selection issues of these PWM control strategies are investigated and addressed. The simulation and field test waveforms are reproduced.
Electric Load-Brake Control for a Small Wind-Turbine Operating in Mountainous Winds
Authors: Ichikawa Yoshimichi , Nishioka Michio , Takami Hideo , Kimura Sigeo
Published: October 2002

The aim of the present study is to contribute to the operation and control of wind turbines situated in mountainous areas, which often suffer from over-speed due to highly gusty mountainous winds with high shear. By adding an electric load-brake to conventional pitch control we can suppress over-speed and increase power production.
Simulation of a Wind Powered Wound Rotor Induction Generator with Slip Power Recovery for Battery Charging
Authors: Perahia J. , Nayar C.V.
Published: October 2002

Blade-tip-speed ratio feedback control is applied to a wind turbine driven, grid connected, three phase, induction generator whose wound rotor winding is connected to a rectifier via slip rings. Power from the rotor winding flows through the rectifier to a switch-mode, step-up, DC to DC converter to re-charge a bank of batteries. The switch in the DC to DC converter has a variable duty cycle, and this design feature is used in a feedback control loop. A dynamic model of the complete system is presented along with simulation results.
The Extent of Hearing Damage from Exposures to Music
Authors: Jaroszewski Antoni
Published: October 2002

Sound pressure levels in discotheques and during training sessions of music students we re measured and analysed. Effects of exposure in the form of permanent and temporary threshold shifts we re determined in the samples of young discotheque attenders and in music students and musicians. The consequences of the threshold shifts in the perception of pitch, loudness, and time are discussed.
Conditioning Monitoring of a Rotor System Having a Slant Crack in the Shaft
Authors: Sekhar A.S.
Published: October 2002

Detection and condition monitoring of a rotor system having a slant crack which occurs because of the fatigue of the shaft due to the torsional moment has been studied. Finite Element (FEM) analysis has been done for flexural vibrations by developing the stiffness matrix of a slant cracked element. Parametric study for eigen values and response has been performed with crack parameters VIZ, crack depth & location and operating and torsional frequencies. The frequency spectra of the steady state responses of the cracked rotor were found to have sub harmonic frequency components at an interval frequency corresponding to torsional frequency, which can be used for crack detection and monitoring.
Active Structural and Acoustic Control of Structure-Borne Road Noise in a Passenger Car
Authors: Sas Paul , Dehandschutter Wouter
Published: October 2002

Within the Brite-Euram Project “Anrava” several active control systems have been evaluated in order to reduce the road noise generated inside the cabin of a mid size station wagon during driving condition on different road surfaces. Different control strategies (feedforward with local and global control, pure feedback) and different approaches (active structural acoustic control and active noise control) have been tested on the car in laboratory conditions and the control performances have been evaluated.

The final control strategies that have been selected based on the results of this study, are based on an adaptive feedforward control algorithm: six accelerameters provide the reference signals and 4 microphones placed inside the cabin give the error feedbacks. Two control configurations, each using a different kind of control source, have been retained : a structural acoustic control system which works with 6 inertial shakers positioned at the main vibration transmission paths of the car suspension, an anti-noise system with 4 loudspeakers inside the cabin.

The paper describes the approaches utilised to design the different control systems and presents the results obtained during laboratory and road tests, comparing them with the performances predicted by numerical simulations.
Prediction of Engine Cooling Fan Noise Radiation
Authors: Wu Sean F.
Published: October 2002

A semi-analytic and semi-empirical formula is developed for predicting noise radiation from engine cooling fan assemblies. In this formula, the tonal sounds centered at the BPF (blade passage frequency) and its harmonics of the fan a re determined by solving fluctuating forces exerted on the surrounding fluid medium by rotating blades, and the narrow and broad band sounds are described by normal distribution-like functions. The effects of shroud, upstream radiator/condenser set, and downstream engine block are approximated by shape functions. The computer model thus obtained is used to calculate the noise spectra from different fan assemblies under various working conditions and validated against the measured data. This model is used to predict the overall sound pressure levels from dimensionally similar fans running under different working conditions, and the results are compared with those estimated by the fan laws currently in use by engineers in the automotive industry.
Radiation Jigsaw: A Different Picture Emerges
Authors: Stewart Alice , Sutcliffe Jill
Published: October 2002

After the bombing of Hiroshima and Nagasaki several study populations of A-bomb survivors were assembled for the purpose of studying genetic, teratogenic and carcinogenic effects of ionising radiation. The recommendations made by the International Commission on Radiological Protection have been largely derived from these studies. However, the recent discovery of significant differences between survivors with and without injuries means that it is no longer safe to base radiation safety regulations on these studies.
Scientific Uncertainty: An Insuperable Obstacle to Compensation for Environmental Causes of Ill Health?
Authors: Miller Chris
Published: October 2002

In this paper, I review the conceptual and legal obstacles faced by those who seek redress for health detriment which is though to be environmental in origin. I use two case studies concerned with radiation: one is related to energy production (paternal pre-conceptional irradiation of workers at a nuclear fuel reprocessing plant), the other involves electricity distribution (the alleged link between leukaemia and power cables). Judicial approaches to scientific uncertainty inherent in these two cases are examined. The more science points to a hitherto unimagined range of threats to human health, the fewer grounds remain for confidence in the capacity of tort to secure appropriate compensation for the putative victims.
Science/ Law Interactions and the Problem of Causation
Authors: Harrison R.J.
Published: October 2002

Traditionally tort (personal injury) cases have been regarded as isolated disputes concerned with individual harm, where the law's role was simply to allocate losses between tortfeasor and victim according to principles of corrective justice. With the advent of the toxic tort – a cause of action which arises when a plaintiff has developed a disease following exposure to a toxic agent (chemical or in the form of energy) has come a fundamental challenge to the traditional basis of causation where under negligence or strict liability the toxic tort plaintiff (like all tort plaintiffs) must establish a causal connection between the tortious conduct and the loss for which recovery is sought. When applying the ‘balance of probability’ test to a toxic tort, two potential problems arise. First the test does not work where there are multiple or even alternative possible causes of a plaintiff's injury. Here the burden of proof demands a degree of certainty in excess of fifty per cent in an area where estimates, probabilities and scientific uncertainty are the norm. Second, difficulties occur in trying to establish the origins of the plaintiff's disease, in particular, the biological mechanism responsible for initiating or mobilising the illness. Underlying the basis of all toxic torts, distinct areas of scientific knowledge, grounded in an epistemological and procedural framework provide the evidence upon which the expert offers his opinion. This article examines the problems that such evidence poses for the legal system and reflects on some of the jurisprudential issues that arose in Reay and Hope v British Nuclear Fuels.
Statistical Analysis Does not Support a Human Influence on Climate
Authors: Singer S. Fred
Published: October 2002

Wigley et al. [1998] have suggested a novel statistical approach for detecting an anthropogenic influence on climate. Their claim is based on the difference they find between the autocorrelation of the (observed) temperature record and that of an unforced climate model (i.e., one in which greenhouse-gas levels do not rise). We examine their analysis in greater detail and find that their conclusion is not valid.
Environmental Impacts of Enhanced Private Property Rights
Authors: McKitrick Ross , Shufelt Timothy
Published: October 2002

There has been concern in western countries over whether strong private property rights empower polluters to the detriment of other citizens. This debate is now playing out in transition economies and developing countries, where the process of moving to a market economy involves strengthening property rights. We review the conflicting arguments and test them using a new international data base. After controlling for income, education and political factors we find that cross-sectional differences in property rights regimes explain some international differences in pollution rates, but changes in property rights laws within a country do not seem to affect emissions.
Directivity of Train Noise in the Vertical Plane
Authors: Chew C. H.
Published: October 2002

Results from field measurements show that train noise exhibits a vertical directivity pattern. Measurements were made for track at grade and track on an elevated viaduct. Both sets of results showed that train noise increased with the angle of elevation, by about 6 dB(A) when the angle of elevation increases from 8° to 30°. A modified train noise model is proposed which could account for the observed vertical directivity pattern as well as matching the train noise profile.
Empirical Prediction of Speech Levels and Reverberation in Classrooms
Authors: Hodgson Murray
Published: October 2002

This paper discusses the development of empirical models for predicting total A-weighted speech levels and 1-kHz early-decay times in classrooms in an arbitrary state of occupancy. These are the two main quantities that affect speech intelligibility in classrooms. Three models for predicting early-decay time were developed. One was based on determining the contributions of various surface features to the average classroom-surface absorption coefficients. The other models, and those for predicting speech levels, were developed using multi-variable linear-regression techniques, and data previously measured in university classrooms or predicted empirically. By way of evaluation, the models were shown to re-predict the average values of the measured quantities in the original data-set with high accuracy, but they tended to underestimate the variability in the data. Predictions are presented to illustrate the performance of the models in the case of small and large hypothetical classrooms with low and high surface absorption, when unoccupied and occupied. The results are consistent with those measured in real classrooms. In particular, the speech-level model predicts physically-realistic decreases with distance from a speaker to a listener. The experimental data has also been used to determine typical ‘effective’ absorption coefficients for three classroom features – carpeted floors, absorbent ceilings and upholstered seating on carpeted floors – data which indicates the real-world performance that can be expected of these features, which may be useful in other prediction models and, for example, which provides information on the choice of treatments to meet the requirements of standards.
Acoustics of the Smolny Cathedral in St. Petersburg
Authors: Pyshin Alexander , Solovejtchik Leonid , Tikhomirov Yuri , Yavorsky Stanislav
Published: October 2002

Results of acoustic measurements in the Smolny Cathedral, one of the most beautiful cathedrals in St. Petersburg, are presented. Values of sound reverberation time, clarity and definition, as well as the structure of early reflections, are obtained and an analysis of the cathedral acoustics given.
Estimation of Reverberation Time in Rectangular Rooms with Non-Uniformly Distributed Absorption Using a Modified Fitzroy Equation
Authors: Neubauer Reinhard O.
Published: October 2002

One of the major objectives of architectural acoustics is to predict the reverberation time in a room. At this time there are several calculation methods to compute the reverberation time, but still Sabine's and Eyring's classical equations are used. In many practical cases the assumption of diffuse sound field conditions for applying Sabine's theory are not in agreement with the existing sound absorption distribution. Therefore, Sabine's formula, as well as other classical reverberation equations like Eyring's or Millington-Sette's, cannot be applied accurately. In 1959 Fitzroy published a paper devoted to the problem of a more accurate calculation of the reverberation time with non-uniformly distributed absorption. In real rooms Fitzroy's equation may therefore become a useful design tool for estimating reverberation time, however, only if it is modified. A modification of Fitzroy's equation is discussed in this paper and some practical examples are presented which compare predicted and measured values of reverberation time in real rooms.

A suggested modification of Fitzroy's equation is presented. Differences between results derived from Fitzroy's, Sabine's, Eyring's and the modified Fitzroy equation as well as results obtained using a room acoustic computer simulation program are compared. Additionally, results are presented and compared using the calculation method of Annex D of prEN 12354-6.
Case Study: The Acoustical Characteristics of Typical Argentinean Classrooms
Authors: Ercoli Liberto , Azzurro Adrián P. , Méndez Antonio M. , Stornini Alberto J.
Published: October 2002

Numerous recent investigations have demonstrated that the acoustical environment in a classroom is an important variable contributing to the academic and psychological achievement of the students. Excessive ambient noise and reverberation in classrooms are serious obstacles for the learning experience because they typically interfere with speech recognition. This study reports on the acoustical qualities and architectural features of typical classrooms in Argentina. It is shown that, in high school and university classrooms studied in Bahia Blanca, the acoustical parameters investigated differ significantly from those recommended by international criteria and guidelines, and so are highly inadequate from an acoustic standpoint.
Can Beam-Block Floors Be Considered Homogeneous Panels regarding Impact Sound Insulation?
Authors: Patrício Jorge
Published: October 2002

This paper presents a study of the acoustic performance of beam-block floors regarding impact noise, modelling them as homogenous floors with the same mass per unit area and same elastic characteristics. The study mainly consisted in the development of a simplified analytical model to characterise impact sound insulation in buildings, according to what is established in the appropriate set of international standards, and in its validation with experimental results. The study was developed under two main lines of investigation: experimental work carried out in laboratory facilities; and the evaluation of the efficiency of the analytical model. The model is based on two methodologies: the modal approach and statistical energy analysis (SEA). The first one applies to the low frequency range and the second one to high frequencies.
Optimum Design of Reinforced Concrete Beams Using Polynomial Optimization Technique
Authors: Dole Rashmi , Ronghe G. N. , Gupta L. M.
Published: October 2002

Structural optimization seeks the selection of design variables to achieve within the limit (constraints) placed on the structural behaviour, geometry or other factors; its goal of optimality defined by the objective function for specified loading conditions. The three basic features design variables, objective function and constraints contrive to form the design problem. There are several mathematical techniques to solve such problems. The polynomial optimization technique is a recently evolved procedure which is concerned with finding the minimum of a polynomial objective function subjected to constraints. A structural design problem has been formulated in this manner which enables minimum cost design to be derived rapidly and simply.

A paper deals with the application of Polynomial optimization technique to R.C.C. beam-member design problem. In the present study this technique is used to determine the minimum cost of reinforced concrete members by considering several design variables such as breadth, depth, area of reinforcing steel etc. Since it is difficult for the designer in the office to become familiar with the mathematical computation required, further attempt is made to represent the resulting optimum design expressions in the form of “Nomograms” which will facilitate the work in the design office.