bluuebunny/crossref_metadata_2025 huggingface dataset:
Time Step Sensitivity of Nonlinear Atmospheric Models: Numerical Convergence, Truncation Error Growth, and Ensemble Design
Authors: Teixeira João , Reynolds Carolyn A. , Judd Kevin
Published: January 2007

Computational models based on discrete dynamical equations are a successful way of approaching the problem of predicting or forecasting the future evolution of dynamical systems. For linear and mildly nonlinear models, the solutions of the numerical algorithms on which they are based converge to the analytic solutions of the underlying differential equations for small time steps and grid sizes. In this paper, the authors investigate the time step sensitivity of three nonlinear atmospheric models of different levels of complexity: the Lorenz equations, a quasigeostrophic (QG) model, and a global weather prediction system (NOGAPS). It is illustrated here how, for chaotic systems, numerical convergence cannot be guaranteed forever. The time of decoupling of solutions for different time steps follows a logarithmic rule (as a function of time step) similar for the three models. In regimes that are not fully chaotic, the Lorenz equations are used to illustrate how different time steps may lead to different model climates and even different regimes. A simple model of truncation error growth in chaotic systems is proposed. This model decomposes the error onto its stable and unstable components and reproduces well the short- and medium-term behavior of the QG model truncation error growth, with an initial period of slow growth (a plateau) before the exponential growth phase. Experiments with NOGAPS suggest that truncation error can be a substantial component of total forecast error of the model. Ensemble simulations with NOGAPS show that using different time steps may be a simple and natural way of introducing an important component of model error in ensemble design.
Dynamic Radiative–Convective Equilibria Using GCM Column Physics
Authors: Held Isaac M. , Zhao Ming , Wyman Bruce
Published: January 2007

The behavior of a GCM column physics package in a nonrotating, doubly periodic, homogeneous setting with prescribed SSTs is examined. This radiative–convective framework is proposed as a useful tool for studying some of the interactions between convection and larger-scale dynamics and the effects of differing modeling assumptions on convective organization and cloud feedbacks.

For the column physics utilized here, from the Geophysical Fluid Dynamics Laboratory (GFDL) AM2 model, many of the properties of the homogeneous, nonrotating model are closely tied to the fraction of precipitation that is large-scale, rather than convective. Significant large-scale precipitation appears above a critical temperature and then increases with further increases in temperature. The amount of large-scale precipitation is a function of horizontal resolution and can also be controlled by modifying the convection scheme, as is illustrated here by modifying assumptions concerning entrainment into convective plumes. Significant similarities are found between the behavior of the homogeneous model and that of the Tropics of the parent GCM when ocean temperatures are increased and when the convection scheme is modified.
The Primary Nonlinear Dynamics of Modal and Nonmodal Perturbations of Monochromatic Inertia–Gravity Waves
Authors: Achatz Ulrich
Published: January 2007

The breaking of an inertia–gravity wave (IGW), initiated by its leading normal modes (NMs) or singular vectors (SVs), and the resulting small-scale eddies are investigated by means of direct numerical simulations of a Boussinesq fluid characterizing the upper mesosphere. The focus is on the primary nonlinear dynamics, neglecting the effect of secondary instabilities. It is found that the structures with the strongest impact on the IGW and also the largest turbulence amplitudes are the NM (for a statically unstable IGW) or short-term SV (statically and dynamically stable IGW) propagating horizontally transversely with respect to the IGW, possibly in agreement with observations of airglow ripples in conjunction with statically unstable IGWs. In both cases these leading structures reduce the IGW amplitude well below the static and dynamic instability thresholds. The resulting turbulent dissipation rates are within the range of available estimates from rocket soundings, even for IGWs at amplitudes low enough precluding NM instabilities. Thus SVs can help explain turbulence occurring under conditions not amenable for the classic interpretation via static and dynamic instability. Because of the important role of the statically enhanced roll mechanism in the energy exchange between IGW and eddies, the turbulent velocity fields are often conspicuously anisotropic. The spatial turbulence distribution is determined to a large degree by the elliptically polarized horizontal velocity field of the IGW.
Model-based fault diagnosis in technical processes
Authors: Frank P. M. , Ding S. X. , Marcu T.
Published: January 2007

In this paper the state-of-the-art developments model-based fault diagnosis in technical processes are reviewed. Attention is focused upon both the analytical approaches that make use of the quantitative models and the knowledge-based approaches using qualitative models. Basic concepts and the advantages as well as disadvantages of different model-based fault diagnosis schemes are outlined.
Nonlinear continuum regression: an evolutionary approach
Authors: McKay Ben , Willis Mark J. , Searson Dominic P. , Montague Gary A.
Published: January 2007

In this contribution, genetic programming is combined with continuum regression to produce two novel nonlinear continuum regression algorithms. The first is a ‘sequential’ algorithm while the second adopts a ‘team-based’ strategy. Having discussed continuum regression, the modifications required to extend the algorithm for nonlinear modelling are outlined. The results of two case studies are then presented: the development of an inferential model of a food extrusion process and an input-output model of an industrial bioreactor. The superior performance of the sequential continuum regression algorithm, as compared to a similar sequential nonlinear partial least squares algorithm, is demonstrated. In addition, the studies clearly demonstrate that the team-based continuum regression strategy significantly outperforms both sequential approaches.
The optimization of a tanker autopilot control system using genetic algorithms
Authors: McGookin Euan W. , Murray-Smith David J. , Li Yun , Fossen Thor I.
Published: January 2007

A genetic algorithm (GA) optimization application is presented in this paper. It involves the performance optimization of a navigation system for a nonlinear tanker model. This navigation system is fully autonomous and regulates the heading of the vessel with reference to a desired course made up of waypoints. The system consists of two components. The first is a line of sight (LOS) autopilot, which determines the desired heading of the tanker from positional information. The second is a heading control system that is derived from sliding mode (SM) control theory. In this investigation the GA is used to optimize the parameters for the SM controller so that the performance of the complete system satisfies specific design criteria. The resulting optimized navigation system is evaluated for different operating conditions for the tanker, e.g., different course, different forward velocities.
Modern heuristic techniques for scheduling generator maintenance in power systems
Authors: Dahal K. P. , McDonald J. R. , Burt G. M.
Published: January 2007

This paper considers the problem of generator maintenance scheduling (GMS) in power systems. The applications of computer-based modern heuristic solutions, namely simulated annealing (SA) and genetic algorithm (GA), are proposed in order to overcome some of the limitations of conventional solution methods. A test problem is formulated as an integer programming problem using a reliability-based objective function and typical problem constraints. The implementation and performance of the solution techniques are discussed. The results obtained demonstrate that these techniques are effective methods for solving GMS problems.
Improvement of a P-wave detector by a bivariate classification stage
Authors: Hernández A. I. , Carrault G. , Mora F.
Published: January 2007

For more than three decades, beat-to-beat detection of electrical atrial activity has been subject of interest in the biomedical field. Several detection schemes and algorithms have been proposed; however, this problem has not been satisfactory solved and remains the main error source for accurate automatic detection and classification of supraventricular arrhythmias, mainly in ambulatory applications and in coronary care units. Some detection methods have been proposed, but none of them have been quantitatively tested or compared, due in part to the lack of a database with annotated P-waves. In this work, a classification stage is proposed as a new decision strategy to improve a P-wave detector previously developed in our laboratory. A quantitative evaluation of the original detector, the proposed classification stage and two other classical P-wave detectors is performed by means of the calculation of their receiver operating characteristics (ROC) curves. Results show the increased performance provided by the new classification stage with respect to the originally developed algorithm and two classical P-wave detection methods.
Modelling a progressive care system using a coloured-timed Petri net
Authors: Hughes M. , Carson E. R. , Makhlouf M. , Morgan C. J. , Summers R.
Published: January 2007

In a progressive care system, patients are transferred between different healthcare units within a healthcare facility, depending on the different stages in the patients’ care. Although a progressive care system allows for improved delivery of treatment and monitoring through the division and specialization of labour and other resources, it is also very problematic to manage effectively with high levels of interdependence between the different units and unpredictable levels of demand that are placed on resources. The solution proposed in this paper is improved scheduling of admissions through the development of a model which may be used as a basis of schedule optimization. The model which will be proposed is designed to assist a human operator to evaluate a schedule by simulating the flow of patients around a progressive care system. The modelling methodology used is coloured-timed Petri nets (CTPNs). It will be argued that the CTPN formalism is particularly suited to the problem since it allows the dynamics of the system to be sensitive to different instantiations of system variables such as processing time. That is, sensitive to different patients having different lengths of stays and admissions requirements.
Transient two-dimensional temperature measurement of open flames by dual-spectral image analysis
Authors: Huang Y. , Yan Y.
Published: January 2007

A novel optical instrumentation system has been developed for on-line continuous measurement of two-dimensional temperature distribution of a combustion flame. The system comprises a special optical assembly, a charged coupled device camera, a frame-grabber and associated software. Based on the two-colour principle, the transient two-dimensional temperature of a flame is determined from the ratio of grey levels of corresponding pixels within two images, which are simultaneously captured at two different wavelengths. Accordingly, the instantaneous two-dimensional temperature distribution of the flame is presented by pseudo-colour. Discreet considerations in the design of the instrumentation system are also described, including the choice of wavelengths, correction of location and intensity of pixels, elimination of noise, and calibration of the instrument factor. A series of experiments was conducted for butane-fired open flames on a combustion test rig. The results show that the temperature of a fuel-rich premixed flame is higher than a diffusion flame and decreases linearly with the equivalence ratio. For a diffusion flame, however, the temperature increases with the fuel flow rate.
Real time evaluation and correction of nonlinear errors in single frequency interferometers
Authors: Wang C. H. , Augousti A. T. , Mason J.
Published: January 2007

Nonlinear errors in single frequency interferometers are mainly caused by inaccuracies in quadrature signals. A novel design for real time correction of these errors has been developed using a technique based on the use of a microcontroller and computational analogue circuits. The former is responsible for the detection of these nonlinear errors while the latter is responsible for their correction. As a result, errors arising from nonlinearity are reduced to about 0.3% of an interference fringe over a bandwidth for the quadrature signals ranging from d.c. to 100 kHz. Moreover, a simplified method for evaluating the degree of these nonlinear errors without resorting to a length standard is also presented. Finally, a demonstration application of this new correction technique to a laser interferometer was carried out and experimental results are given.
An optical fibre sensor for particle concentration measurement in water systems based on inter-fibre light coupling between polymer optical fibres
Authors: Zhang F. H. , Lewis E. , Scully P. J.
Published: January 2007

An optical fibre sensor has been developed to measure particle concentration in water. The principle of operation is based on light being coupled between two parallel mounted fibres in the vicinity of the sensing region. The optical power is coupled by means of the evanescent field of the multimode fibres. A theoretical description of the light propagation mechanism in the fibre is presented which is extended to include the effect of attenuation of the evanescent wave in the measurand medium. Experimental results are also presented for yeast suspensions in water in the range 0-16 gl-1.
Using electromagnetic methods to monitor the transformation of steel samples
Authors: Johnstone S. , Binns R. , Peyton A. J. , Pritchard W. D.N.
Published: January 2007

This paper describes several electromagnetic sensing arrangements for measuring the percentage of austenite, which has transformed into ferrite in hot rolled steel as it cools. The results from laboratory experiments are presented. These indicate that all the sensors produce outputs, which are associated with the percentage transformation. Using the knowledge gained from this work it is proposed to build an on-line trial sensor for use in a hot strip mill.
Control of bounded dynamic stochastic distributions using square root models: an applicability study in papermaking systems
Authors: Wang H. , Baki H. , Kabore P.
Published: January 2007

Following the recent developments on the modelling and control algorithms of the shape of the output probability density function for general dynamic stochastic systems (Wang, 1998a, Proceedings of the IFAC Workshop on AARCT, Cancun, pp. 95-99), this paper presents a square root approximation-based control algorithm, where the B-splines function expansion is used to approximate the square root of the output probability density function in order to guarantee its positiveness. It has been shown that with such an approximation, the system is generally nonlinear. This is true even when the dynamic part of the system is linear. As such, a nonlinear control algorithm has been developed to control the output probability density function of the system. A simulated example is used to demonstrate the use of the algorithm and encouraging results have been obtained.
Kalman filters applied to actively controlled railway vehicle suspensions
Authors: Mei T. X. , Li H. , Goodall R. M.
Published: January 2007

This paper studies the development and application of Kalman filters for actively controlled railway vehicle suspensions. The basic requirement of state estimation for active suspensions of railway vehicles is discussed and two distinct track features that affect the design of a state observer are highlighted. Two effective methods to accommodate the different track characteristics based on two detailed case studies are presented in the paper. The principles described, however, apply to other uses of model-based estimation on railway vehicles. In the first study a state observer for the plan-view model of a two-axle vehicle is developed, primarily for the active steering of railway wheelsets. The observer using Kalman filters is formulated not only to estimate all necessary vehicle states, but also to include and hence estimate as part of the state variables the curve radius and cant of the railway track on which the vehicle is travelling. In the second study, Kalman filters are used to estimate state variables of the side-view model of a quarter car. The output is then used to implement the (active) vertical suspension using the principle of ‘skyhook’ damping in order to optimize the trade-off between the random and deterministic input requirements.
Robust control of a magnetic-bearing flywheel using dynamical compensators
Authors: Duan Guang-Ren , Wu Zhan-Yuan , Howe David
Published: January 2007

This paper considers the robust control of a current-controlled magnetic bearing with a pair of opposing electromagnets and a rigid rotor. A first-order dynamical compensator which uses only position feedback information is applied for control. The dynamical compensator design is based on a linearized one-dimensional second-order linear model, which is treated as an interval system in order to cope with parameter uncertainties. Through robust stability analysis, a parameterization of all the first-order robust stabilizing dynamical compensators for the interval magnetic-bearing system is first obtained. Then, by appropriately selecting the free parameters in the robust stabilizing controller, the H-two norm of the disturbance-output transfer function is made arbitrarily small over the system parameter intervals, and the H-infinity norm of the output-input transfer function is made arbitrarily close to a lower bound. The proposed approach is applied to control a flywheel supported by active magnetic bearings. Simulation and experimental results show that this approach is simple, effective and very robust.
An investigation into a rolling process for the attachment of resin rubber soles to shoes
Authors: Bicker R. , Taylor P. M. , Brady S. M. , Reedman D. C.
Published: January 2007

The paper describes the results of mechanical rolling tests carried out using a resin rubber sheet material to establish the effects of roller pressure and differential roller speed on the subsequent distortion of the material. The justification for conducting these tests is based on the motivation to automate the attachment of shoe soles to lasted uppers as part of the final assembly operation in shoe manufacture. The design of a prototype experimental rolling rig is described and the test procedure outlined. The tests carried out suggest that it is possible to both extend and contract the length of a sample of resin rubber material whilst simultaneously bonding the material onto a flat surface representative of a shoe upper. Extensions of more than 1% were obtained using a roller differential speed of 2% (equivalent to 2 mm in length), and normal load of 3 kg. However, substantial differential speeds of up to -15% were required to bring about a compression of only 0.5% of the sample. Under these conditions it is probable that slip occurs between the roller surface and the sample.
Impacts of mass movement erosion on land productivity: a review
Authors: Blaschke Paul M. , Trustrum Noel A. , Hicks Douglas L.
Published: January 2007

Wherever people gain their livelihood in mountains and steeplands, the productive capacity of the soils they use is likely to be affected by mass movement erosion. The impacts of mass movement erosion on land productivity are significant but under-rated in the scientific literature. Impacts on cropping are here reported from 15 countries in south and southeast Asia, east Africa, the Caribbean and Melanesia, but accounts are generalized or anecdotal, and do not quantify crop loss or damage attributable to mass movement separately from that due to surface or fluvial erosion. Impacts on pastoral grazing have been studied in New Zealand, where production losses of up to 80% at field scale, and up to 20% at farm scale, have been measured. Studies in the Pacific Northwest coastal forests of North America show plantation forest wood volume declines by 35-50% on eroded sites. Mass movement impacts on production from tropical forests or agroforestry appear to be as yet undocumented.

The reasons for lack of documentation are, first, that most soil erosion-productivity research has been done on gently sloping cropland, which is subject to surface rather than mass movement erosion. Secondly, geomorphological research in steeplands has dealt with mass movement as a hazard to human life, settlements and infrastructure -with limited identification of its contribution to sediment loads in rivers, and disregarding its impact on land productivity.

We suggest there are many other countries where significant impacts are likely to occur, and that erosion-productivity studies should pay more attention to this type of erosion. Studies should not be restricted to cropland, but also extend to grazing land, plantation forestry, agro-forestry and traditional uses of natural forest as mass movement appears to affect all these forms of land-based production, particularly in densely populated steeplands whether tropical or temperate. Topics needing study are the documentation and costing of productivity losses, ways to reduce mass movement impacts on productivity, and ways to enhance recovery of soil on eroded areas (e.g., revegetation with fertility-building shrubs and legumes).
Chinese loess and the evolution of the east Asian monsoon
Authors: Huang Chun Chang , Pang Jiangli , Zhao Jingpo
Published: January 2007

The history of the east Asian monsoon has been reconstructed from proxy records from the aeolian loess-palaeosol sequence in the Loess Plateau. It has been suggested that the monsoonal atmospheric circulation was initiated abruptly at 2.6 M yr BP. From about 1.2 M yrBP, the climate was characterized by contrasts between dry-cold periods brought on by the northwesterly monsoon and humid-warm periods brought about by the southeasterly monsoon. The periodic changes related to the earth’s orbital cycles have been clearly identified. Since about 0.6 M yr BP, the monsoonal climatic variations have become extremely pronounced and these correlate well with the marine isotope stages. The three-step shift in the east Asian monsoon towards greater variation seems to have been caused by the accelerated uplifting of the Tibetan Plateau. Climatic change during the last interglacial-glacial cycle recorded in the loess seems to match the SPECMAP δ18O record exactly. Six episodes of extremely strong dustfall events (brought on by the strengthened northwesterly monsoon winds) have been identified during the last glaciation. The ages of these episodes seem to match the Heinrich events in the North Atlantic and the Dansgaard-Oeschger events in Greenland. It is therefore suggested that the atmospheric circulation in east Asia is very sensitive to climatic change in high latitudes and has been responsive to global climatic change over the last 2.6 M yr. Millennial-scale climatic variations have also been identified in the Holocene loess. The article concludes by suggesting areas of research that might be undertaken in order to improve our understanding of the Chinese loess and of the evolution of the east Asian monsoon.
Sediment transport capacity relations for overland flow
Authors: Prosser Ian P. , Rustomji Paul
Published: January 2007

Nearly all physically based models of soil erosion and landform evolution include an equation for the sediment transport capacity of flow, yet the choice of relation varies from one model to another. This raises the question of the empirical and theoretical support for particular choices. We review descriptions of the effect of discharge and slope on sediment transport capacity of overland flow. A limited range of relations is defined for which there is strong theoretical and empirical support. Nevertheless, suggestions are made for improved experimental designs that further evaluate theories of sediment transport capacity and reduce uncertainty in its application to catchment modelling of sediment transport.
Estimating trap efficiency of small reservoirs and ponds: methods and implications for the assessment of sediment yield
Authors: Verstraeten Gert , Poesen Jean
Published: January 2007

Throughout the world, several millions of small ponds exist for water supply, irrigation, flood control or to control water quality downstream. The reduced flow velocity in these ponds causes sedimentation of tranported particles. For most ponds this is a negative impact as their retention capacity decreases due to sedimentation processes. Sediment volumes in small ponds can be used to reconstruct sediment yield values and to study the spatial variation in sediment yield over large areas. Especially in developing countries, this technique can be very helpful in establishing large data sets on sediment delivery as there are often no resources for expensive monitoring programmes. However, when such studies are undertaken, one has to take into account the efficiency of the pond in trapping sediments. This trap efficiency is dependent on the characteristics of the inflowing sediment and the retention time of the water in the pond, which in turn are controlled by pond geometry and runoff characteristics. Because trap efficiency is one of the most important properties of a pond or reservoir, it has been studied for quite some time. This article provides an overview of the different methods available to estimate the trap efficiency of reservoirs and ponds. The first set of methods are empirical models that predict trap efficiency, mostly of normally ponded large reservoirs using data on a mid to long-term basis. These models relate trap efficiency to a capacity/watershed ratio, a capacity/annual inflow ratio or a sedimentation index. Today, these models are the most widely used models to predict trap efficiency, even for reservoirs or ponds that have totally different characteristics from the reservoirs used in these models. For small ponds, these models seem to be less appropriate. They also cannot be used for predicting trap efficiency for a single event. To overcome these restrictions, different theoretical models have been developed based on sedimentation principles. These can be very simple, such as the overflow rate method, but also very complex when runoff and sediment are routed through a pond with incremental time-steps. The theoretical-based models are probably more capable of predicting trap efficiency for small ponds with varying geometric characteristics, and some of them also provide data on effluent sediment concentrations and quality. However, when reconstructing sediment yield values using sedimentation rates over a period of a few months to a few year (the mid-term basis), one needs a trap efficiency value for the whole period, not for one single event. At present only limited research has been done on establishing mid-term trap efficiency models based on theoretical principles. This is probably the most important gap in trap efficiency research.
Shore platforms: a neglected coastal feature?
Authors: Stephenson W. J.
Published: January 2007

This review identifies four themes in shore platform research: 1) the role of marine and subaerial processes in platform development; 2) morphology of shore platforms; 3) modelling platform development; and 4) measuring rates of erosion. The view that shore platforms have a wave-cut origin has dominated the literature in the last 20 years. It is argued that this wave-cut origin remains to be convincingly demonstrated. Attempts to link platform morphology with the process environment have proven difficult but a recent demarcation between platform morphologies based on wave erosion and rock resistance offers an interesting and new way to consider platform morphology. Attempts to model platform development have been handicapped by a lack of data and a clear understanding of development processes. All models are based on the premise that platforms have a wave-cut origin, yet this has not been adequately demonstrated. There are a number of contradictions between models that require resolution. Erosion rates have been measured using the micro-erosion meter, but these studies are restricted both temporally and spatially. The contribution of microscale erosion relative to other forms and scales remains unknown. A number of issues are raised and suggested as being suitable questions for future research. It is proposed that real advances in understanding shore platforms will be aided by collaborative work between researchers from a number of morphogenetic environments.
Plant functional types: an alternative to taxonomic plant community description in biogeography?
Authors: Duckworth Jennifer C. , Kent Martin , Ramsay Paul M.
Published: January 2007

This article critically reviews the concept of plant functional types as an alternative to the traditional taxonomic species-based approach to plant community description in biogeography and ecology. Originally formulated in the last century, there has been an acceleration in interest in the concept over the last decade. Plant functional types are nonphylogenetic groupings of species that show close similarities in their response to environmental and biotic controls. Functional classifications often cut across taxonomic classifications and may be more meaningful in terms of plant response, in addition to overcoming certain problems associated with the traditional taxonomic species-based approach.

Plant functional types are derived from traits based on species morphology, physiology and/or life history, depending on the aims and scale of the research. Whilst some traits can be measured in the field, others require more detailed laboratory measurement and experimentation. A trade-off exists between the time and efficiency gained from using simple traits and those requiring more elaborate analysis, although certain ‘key traits’ may act as easily measured surrogates for others.

Practical applications of plant functional types in biogeography and ecology are also reviewed. Plant functional types can aid in the understanding of ecological processes, such as the assembly and stability of communities and succession, and facilitate the detection and prediction of response to environmental change at a range of scales. Despite its potential, the plant functional type approach is probably best viewed as a complementary approach to description using traditional taxonomy.
Desert dune processes and dynamics
Authors: Wiggs Giles F.S.
Published: January 2007

This article reviews the advances made and problems encountered in the measurement, modelling and understanding of desert dune dynamics and processes in the last two decades. The main findings of three methods of investigation are reviewed: field studies, wind tunnel studies and mathematical modelling. Whilst major advances in field techniques have allowed an appreciation of the aerodynamic nature of sand dunes, particular problems with field research are evident in the measurement of aeolian processes on dune surfaces. Specifically, it is shown that attempts to ascertain shear stresses on dune windward slopes in the field and relate changes in stress to sand transport rate and erosion/deposition measurements have generally failed. These difficulties have arisen because the non-log-linear nature of wind velocity profiles on dune surfaces as a result of windflow acceleration has made the calculation of surface shear stresses unviable. Significant advances have been achieved in wind tunnel modelling where high-frequency hot-wire anemometer measurements have enabled shear stress and turbulence characteristics to be determined, although problems have been encountered in choosing appropriate scaling parameters. Empirical field and wind tunnel data have allowed the calibration of mathematical models which are now at a stage where the flow field around dunes can be calculated. It is considered, however, that the emerging technique of modelling using complex systems theory may hold the key to constructing a reliable framework for future investigations. New complex systems models have emphasized the need to return to a larger-scale perspective where dunes are not considered as individual elements, but as an integral part of a dunefield where aeolian processes at the dune scale are not thought to be significant.
Geostatistics and remote sensing
Authors: Curran Paul J. , Atkinson Peter M.
Published: January 2007

In geostatistics, spatial autocorrelation is utilized to estimate optimally local values from data sampled elsewhere. The powerful synergy between geostatistics and remote sensing went unrealized until the 1980s. Today geostatistics are used to explore and describe spatial variation in remotely sensed and ground data; to design optimum sampling schemes for image data and ground data; and to increase the accuracy with which remotely sensed data can be used to classify land cover or estimate continuous variables. This article introduces these applications and uses two examples to highlight characteristics that are common to them all. The article concludes with a discussion of conditional simulation as a novel geostatistical technique for use in remote sensing.
Infiltration into soils, with particular reference to its visualization and measurement by magnetic resonance imaging (MRI)
Authors: Amin M. H.G. , Hall L. D. , Chorley R. J. , Richards K. S.
Published: January 2007

This article draws attention to the potential of magnetic resonance imaging (MRI) for studies of patterns and mechanisms of water infiltration into soils, and stresses the vitally important need for collaboration between hydrologists, soil physicists and MRI experts. A brief introduction of the principles of MRI is given. This is followed by a review of the literature relating to nonpreferential infiltration, preferential infiltration exhibiting fingering and preferential infiltration involving a wide range of macropore flow. These differing degrees of complexity of infiltration dynamics require the employment of noninvasive and nondestructive techniques for their detailed investigation. Finally, an overview of applications of MRI to the detection of the spatial and temporal distribution of soil moisture and its changes is given. General conclusions are drawn from previous and current research, and the potential of the application of MRI to infiltration studies is summarized.
Recent climate variability and future climate change scenarios for
Authors: Britain Great , Conway D.
Published: January 2007

This article reviews recent climatically extreme periods in Great Britain and presents results from the latest general circulation model (GCM) experiments showing the possible spatial patterns and magnitude of future climate change for this region. During the last decade the British Isles has seen record-breaking periods of above-average temperatures, alongside periods with above and below-average precipitation, combined with an increase in winter precipitation and a decrease in summer precipitation. The impacts of these anomalies, coupled with the possibility that future climate change may increase their frequency and/or severity, have prompted the UK Department of the Environment, Transport and Regions and other organizations involved in environmental management, such as the Environment Agency, to commission a number of studies into their impacts. These have highlighted wide-ranging impacts on the natural environment of Great Britain and on human ativities to the extent of affecting the national economy.

The use of GCMs for the development of future climate change scenarios is reviewed. Results from recent ensemble GCM experiments with and without the effects of sulphate aerosols are presented. These show broadly similar changes in temperature and precipitation to previous climate change scenarios prepared for Great Britain. In summary, the scenarios suggest the following: a warming of about 3 8C (3.5 8C) over the region by 2100 with (without) the effects of sulphate aerosols; slight increases in annual precipitation over northern England and Scotland, more pronounced increases over the whole of the region in winter; and slight decreases in precipitation over Wales and central England in summer. These changes are synchronous with decreases in the number of wet-days and increases in the intensity of precipitation on wet-days. The high level of uncertainty associated with regional scenarios of temperature and precipitation is discussed and emphasized
On the origin, nature and uses of Antarctic ice-sheet radio-echo layering
Authors: Siegert Martin J.
Published: January 2007

Airborne radio-echo sounding (RES) data display layering within the Antarctic ice sheet. At ice depths below 1000m these layers are caused by horizons of ice with relatively high acidity which were originally deposited on the ice surface after large volcanic events. Layering which is less than 1000 m from the ice surface can also be due to variation in ice density. Theoretically, therefore, internal RES layering below 1000 m should represent isochronous planes. This theory is upheld under examination of existing RES data where internal layers have been observed to follow the rules of superposition. For example, RES layers are deposited as discrete bands, fold and fault in a manner analogous to geological features, never cross over each other and, in an undisturbed deposit, have a depth-age relationship which means that the oldest layers are located at the lowest level. Moreover, the location of internal layering is independent of radiowave receiver altitude, the frequency of the radiowave does not affect layer depth, and the pulse width of the e/m wave does not affect identification of layers. Thus, RES reflects actual dielectric layering within the ice sheet. Glaciologists use RES layering for a number of reasons, including: (1) correlating ice cores; (2) as boundary conditions for numerical models to help determine the direction of ice flow; and (3) as a means of identifying the three-dimensional ice-sheet geometry and architecture.
Coastal geomorphology in New Zealand, 1989-99
Authors: Hesp P. A. , Shepherd M. J. , Parnell K.
Published: January 2007

This article reviews coastal geomorphological research published in New Zealand or international journals which has been carried out in New Zealand during the past ten years. All coastal environments are covered, including tidal inlets, estuaries and lagoons, beach, surfzone, nearshore and shelf environments, and rocky coasts. Applied coastal studies are also covered. While the New Zealand coastal science community remains relatively small, a significant body of work has been carried out, much of it innovative and unique. However, with 11 000 km of very diverse coastline covering 13 degrees of latitude available for study, there are many areas, geographical as well as disciplinary, that remain poorly researched.
Applied physical geography in New Zealand
Authors: Kirk R. M. , Morgan R. K. , Single M. B. , Fahey B.
Published: January 2007

Physical geographers in New Zealand have a tradition of applied research in a variety of contexts, including environmental management as well as soil, vegetation and landform systems conservation. In recent years this work has been given new impetus (with the promise of even greater involvement) as a result of economic restructuring at the national level, restructuring of government departments and agencies dealing with environmental and resource management and conservation, the introduction of new statutes relating to environmental and resource management, and major changes in the funding and management of science research in the public sector.

This article provides an overview of the institutional environment within which New Zealand physical geographers now carry out applied work. The contemporary resource management and legislative contexts are described and structural changes that have taken place in New Zealand science over the last decade are reviewed. Research undertaken by the authors or their research students provides examples of the different types of work now being undertaken by physical geographers in New Zealand under the new legislative and funding regimes. Two examples are described in detail. The first is drawn from research dealing with catchment hydrology and water supply and has been undertaken by a physical geographer employed by Landcare Research, a Crown-owned research company. The second comes from work carried out by two university-based physical geographers into the environmental effects on coasts of a new mode of marine passenger transport (`fast ferries'), to meet the requirements of new environmental legislation.
River morphology and management in New Zealand
Authors: Mosley P. , Jowett I.
Published: January 2007

River research in New Zealand is strongly conditioned by management requirements defined by environmental legislation. Principal areas of investigation at present include information on river morphology, habitat and instream flows required for management of fluvial ecosystems; erosion, sediment transport and sediment yield; and gravel-bedded and braided river processes. Research in these areas has tended to have a strong orientation towards field observations as a basis for developing quantitative (commonly statistical) models, and ultimately the provision of guidance material and decision support systems for resource managers. A fourth area of particular emphasis has been channel networks and hydraulic geometry. Again, the work generally has been field-intensive, but has been directed towards testing models such as the optimal channel network concept. Current research directions are focusing particularly on gravel-bed river mechanics, climatic and tectonic controls on landscape evolution, and instream habitat hydraulics and ecosystems.
Mesoscale and local climates in New Zealand
Authors: P. Sturman Andrew , A. McGowan Hamish , A. Spronken-Smith Rachel
Published: January 2007

New Zealand is a country of marked local and regional environmental variability. The complexity of the terrain and significant relief of this island nation surrounded by extensive areas of ocean produce rapid changes of climate over relatively short distances. This article provides a selective review of recent research into the mesoscale and local climates of this interestingly varied environment. Research completed on energy budgets of the varying surface types provides the starting point for an assessment of thermal effects on the atmospheric boundary layer and airflow. The dynamic effects of surface topography are also seen to have a major impact on regional and local airflow patterns, as well as on mesoscale variations of convection and precipitation. It is clear that the interaction of mid-latitude synoptic weather systems with the mountains of New Zealand produces distinct patterns of wind and rainfall that have a major impact on the physical and human environment of the country. The föhn nor'wester and southerly changes are significant local meteorological phenomena, while mesoscale climate processes are increasingly recognized as important for agricultural activities, the management of hydrological systems and in dealing with environmental problems such as air pollution.
Central American Grandparents Raising Grandchildren
Authors: Fuller-Thomson Esme , Minkler Meredith
Published: January 2007

This study documents the prevalence and profile of Central American grandparents raising grandchildren in the United States of America. Using nationally representative data from the Census 2000 Supplementary Survey, Central American grandparent caregivers are compared with their noncare-giving peers. Results indicate that nationally an estimated 28,000 Central Americans were raising their grandchildren, representing approximately 1 in 20 Central Americans aged 45 and older. Caregiving grandparents were significantly younger and more likely to be married, to have not completed high school, and to be out of the labor force than were noncaregivers. Almost half of caregiving households were overcrowded and approximately a quarter were below the poverty line. Only 1% of caregivers who were living in poverty were accessing social assistance. Implications for practice and policy are discussed.
Examining Drinking Consequences and Reasons for Drinking in a Bilingual College Sample
Authors: Orona J. Arturo , Blume Arthur W. , Morera Osvaldo F. , Perez Solanja
Published: January 2007

College drinking behavior is a national public health concern. However, little research has been conducted to test the psychometric validity and reliability of alcohol use measures among Spanish-speaking Hispanic college students. Adopting a translation-back-translation approach, the Rutgers Alcohol Problem Index (RAPI) was translated into Spanish and the Razones del Consumo de Alcohol (RCA), a newly created measure of one’s reasons for drinking, was developed in Spanish. Both measures were administered to 155 Spanish-speaking students at a university in the Southwestern United States. All translated measures demonstrated adequate internal consistency reliability. Support for the construct validity of the translated RAPI measure was demonstrated as gender and RCA scores were predictive of RAPI scores in their expected directions [ R2 = .438, F(2, 138) = 53.36, p = .000]. Acculturation was not significantly associated with RAPI scores nor did acculturation interact with RCA scores to enhance the predictability of RAPI scores. Finally, an exploratory factor analysis was performed on the RCA revealing a one-factor solution as the most adequate description of the RCA data. Knowledge of reasons for drinking as assessed by the RCA seems useful in predicting drinking-related consequences among Hispanic college students.
Histochemical demonstration of changes in the activity of hepatic phosphatases induced by experimental lead poisoning in male white rats (Rattus norvegicus)
Authors: Jarrar Bashir M. , Mahmoud Zuheir N.
Published: January 2007

Seven hepatic phosphatases were histochemically investigated in male white rats ( Rattus norvegicus) pretreated with chronic subtoxic doses of lead acetate. Lead has increased the activities of alkaline-, acid-, neutral-, adenosine mono- and glucose-6-phosphatase, but has markedly decreased the activity of membrane-bound Na+—K+, ATPase while the activity of mitochondrial Mg2+ -ATPase was not altered. It has also produced heterogenous alterations in the distribution patterns, sites of the enzymatic activities and in the intensity of phosphatase activities among the same type of cells in the terminal afferent and efferent venules of the hepatic lobules. The obtained histochemical findings indicate that the alterations in the activities of hepatic phosphatases could be an adaptation to the metabolic, structural and functional changes in the organelles of hepatic cells due to lead intoxication.