This book contains a collection of the main contributions from the first five workshops held by Ercoftac Special Interest Group on Synthetic Turbulence Models (SIG42. It is intended as an illustration of the sig's activities and of the latest developments in the field.

Thisvolume investigates the use of Kinematic Simulation (KS) and other synthetic turbulence models for the particular application to environmental flows.

Thisvolume offers the best syntheses on the research status in KS, which iswidely used in various domains, including Lagrangian aspects in turbulence mixing/stirring, particle dispersion/clustering, and last but not least, aeroacoustics. Flow realizations with complete spatial, and sometime spatio-temporal, dependency, are generated via superposition of random modes (mostly spatial, and sometime spatial and temporal, Fourier modes), with prescribed constraints such as: strict incompressibility (divergence-free velocity field at each point), high Reynolds energy spectrum. Recent improvements consisted in incorporating linear dynamics, for instance in rotating and/or stably-stratified flows, with possible easy generalization to MHD flows, and perhaps to plasmas. KS for channel flows have also been validated. However, the absence of "sweeping effects" in present conventional KS versions is identified as a major drawback in very different applications: inertial particle clustering as well as in aeroacoustics. Nevertheless, this issue was addressed in some reference papers, and merits to be revisited in the light of new studies in progress. "

Turbulence is a dangerous topic which is often at the origin of serious fights in the scientific meetings devoted to it since it represents extremely different points of view, all of which have in common their complexity, as well as an inability to solve the problem. It is even difficult to agree on what exactly is the problem to be solved. Extremely schematically, two opposing points of view have been advocated during these last ten years: the first one is "statistical", and tries to model the evolution of averaged quantities of the flow. This com has followed the glorious trail of Taylor and Kolmogorov, munity, which believes in the phenomenology of cascades, and strongly disputes the possibility of any coherence or order associated to turbulence. On the other bank of the river stands the "coherence among chaos" community, which considers turbulence from a purely deterministic po int of view, by studying either the behaviour of dynamical systems, or the stability of flows in various situations. To this community are also associated the experimentalists who seek to identify coherent structures in shear flows.

The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry.

The author's experience indicates that students, after 40 lectures and exercisesof 45 minutesbasedon this textbook, have proved capable of designing independently complex heat exchangers such as for cooling of rocket propulsion chambers, condensers and evaporators for heat pumps."

Flow Control Methods and Devices in Micrometer Scale Channels, by Shuichi Shoji and Kentaro Kawai. Micromixing Within Microfluidic Devices, by Lorenzo Capretto, Wei Cheng, Martyn Hill and Xunli Zhang. Basic Technologies for Droplet Microfluidics, by Shaojiang Zeng, Xin Liu, Hua Xie and Bingcheng Lin. Electrorheological Fluid and Its Applications in Microfluidics, by Limu Wang, Xiuqing Gong and Weijia Wen. Biosensors in Microfluidic Chips, by Jongmin Noh, Hee Chan Kim and Taek Dong Chung. A Nanomembrane-Based Nucleic Acid Sensing Platform for Portable Diagnostics, by Satyajyoti Senapati, Sagnik Basuray, Zdenek Slouka, Li-Jing Cheng and Hsueh-Chia Chang. Optical Detection Systems on Microfluidic Chips, by Hongwei Gai, Yongjun Li and Edward S. Yeung. Integrated Microfluidic Systems for DNA Analysis, by Samuel K. Njoroge, Hui-Wen Chen, Ma gorzata A. Witek and Steven A. Soper. Integrated Multifunctional Microfluidics for Automated Proteome Analyses, by John K. Osiri, Hamed Shadpour, Ma gorzata A. Witek and Steven A. Soper. Cells in Microfluidics, by Chi Zhang and Danny van Noort. Microfluidic Platform for the Study of Caenorhabditis elegans, by Weiwei Shi, Hui Wen, Bingcheng Lin and Jianhua Qin."

The present volume, with the exception of the introductory chapter, consists of papers delivered at the workshop entitled "The Impact of Supercomputers on the Next Decade of Computational Fluid Dynamics," The workshop, which took place in Jerusalem, Israel during the week of December 16, 1984, was initiated by the National Science Foundation of the USA (NSF), by the Ministry of Science and Development, Israel (IMSD), and co-sponsored by the National Aeronautics and Space Administration (NASA), the Office of Scientific Research of the U.S. Air Force (AFOSR), Tel Aviv University and Massachusetts Institute of Technology. The introductory chapter attempts to summarize what transpired at the workshop. The genesis of the workshop was an agreement between NSF and Il1S, signed in the spring of 1983, to conduct a series of bi-national work shops and symposia. This workshop represented the first activity spon sored under the agreement. The undersigned were selected by their respective national bodies to act as co-coordinators and organizers of the workshop. The first question that we faced was to decide upon a topic. In the past few years the field of CFD has mushroomed and consequently there have been many meetings, symposia, workshops, congresses, etc."

The book presents a state-of-the-art in environmental aerodynamics and the structural design of wind energy support structures, particularly from a modern computational perspective. Examples include real-life applications dealing with pollutant dispersion in the building environment, pedestrian-level winds, comfort levels, relevant legislation and remedial measures. Design methodologies for wind energy structures include reliability assessment and code frameworks.

The field of shock compression science has a long and rich history involving contributions of mathematicians, physicists and engineers over approximately two hundred years. The middle of the nineteenth century was an especially ac tive period with the contributions of Riemann, Rankine and Hugoniot, among others. The middle of the twentieth century saw another increase in activity re lated to shock compression of condensed matter as a result of military applica tions. It was also recognized that shock compression provided a means of sub jecting solids and liquids to extreme states of temperature and pressure difficult to achieve by static means. It has thus become an academic study in its own right. The principal modem contributions to this science were summarized in the landmark paper by Rice, McQueen and Walsh [Solid State Physics, Vol. 6, pp. 1-63, 1958]. As this field has continued to mature, interest has increased in tracing the early papers that have served as the foundations of the field. Cheret [Shock Compression of Condensed Matter - 1989, Elsevier Sci. Pub. B. V. , pp 11-19, 1990) has contributed to this literature with his review of the life of Hugoniot on the one-hundredth anniversary of the publication of Hugoniot's classic paper on the propagation of discontinuous waves in gases. This contribution prompted additional historical investigation involving the precursors to Hugoniot.

The present Volume 4 of the successful monograh package Multiphase Flow Dynamics is devoted to selected Chapters of the multiphase fluid dynamics that are important for practical applications but did not find place in the previous volumes. The state of the art of the turbulence modeling in multiphase flows is presented. As introduction, some basics of the single phase boundary layer theory including some important scales and flow oscillation characteristics in pipes and rod bundles are presented. Then the scales characterizing the dispersed flow systems are presented. The description of the turbulence is provided at different level of complexity: simple algebraic models for eddy viscosity, simple algebraic models based on the Boussinesq hypothesis, modification of the boundary layer share due to modification of the bulk turbulence, modification of the boundary layer share due to nucleate boiling. The role of the following forces on the mathematical description of turbulent flows is discussed: the lift force, the lubrication force in the wall boundary layer, and the dispersion force. A pragmatic generalization of the k-eps models for continuous velocity field is proposed containing flows in large volumes and flows in porous structures. A Methods of how to derive source and sinks terms for multiphase k-eps models is presented. A set of 13 single- and two phase benchmarks for verification of k-eps models in system computer codes are provided and reproduced with the IVA computer code as an example of the application of the theory. This methodology is intended to help other engineers and scientists to introduce this technology step-by-step in their own engineering practice.

In many practical application gases are solved in liquids under given conditions, released under other conditions and therefore affecting technical processes for good of for bad. Useful information on the solubility of oxygen, nitrogen, hydrogen and carbon dioxide in water under large interval of pressures and temperatures is collected, and appropriate mathematical approximation functions are provided. In addition methods for the computation of the diffusion coefficients are described. With this information solution and dissolution dynamics in multiphase fluid flows can be analyzed. For this purpose the non-equilibrium absorption and release on bubble, droplet and film surfaces under different conditions is mathematically described.

A systematic set of internally consistent state equations for diesel fuel gas and liquid valid in broad range of changing pressure and temperature is provided.

This new second edition includes various updates, extensions, improvements and corrections.

In many practical application gases are solved in liquids under given conditions, released under other conditions and therefore affecting technical processes for good of for bad. Useful information on the solubility of oxygen, nitrogen, hydrogen and carbon dioxide in water under large interval of pressures and temperatures is collected, and appropriate mathematical approximation functions are provided. In addition methods for the computation of the diffusion coefficients are described. With this information solution and dissolution dynamics in multiphase fluid flows can be analyzed. For this purpose the non-equilibrium absorption and release on bubble, droplet and film surfaces under different conditions is mathematically described.

A systematic set of internally consistent state equations for diesel fuel gas and liquid valid in broad range of changing pressure and temperature is provided.

This new second edition includes various updates, extensions, improvements and corrections.

In the last decades, a lot of effort has been directed towards manipulation of turbulent boundary layers by passive devices such as external manipulators (thin flat plates or aerofoil section devices embedded in the outer layer) and/or internal manipulators (small streamwise grooves acting directly on the inner region) for the purpose of reducing viscous drag. The former are commonly referred to as LEI3U s or BLADEs and the laHer riblets or grooves. Though the details of the mechanisms are not firmly understood, world-wide experimenta.! data are available and consistent enough in order to assert the potential of such devices for turbulent drag reduction. It should be noted that following on from recent and successful flight tests, the concept of using grooved surfaces is rather close to finding industrial applications. During the last few years, in Europe, there has been considerable interest in lookillg at the behaviour of such passi,'e turbulence manipulators. A lot of intense research, concerning both experimental and theoretical studies. has been carried out in some European research centres. For the last fi\'e years. informal gatherings. called ,.\ \'orking Pi\l'ty i\Ieetings" , have been set up, once a year; the aim of these meetings is not only to bring together European researchers acti,'e in the field of turbulent drag reduction by passi"e means and to hear about recent de\'c!opments but also to o u t1 ine sui tit ble directions for future research or collaborative programmes.

This book contains the course notes of the Summerschool on High Performance Computing in Fluid Dynamics, held at the Delft University of Technology, June 24-28, 1996. The lectures presented deal to a large extent with algorithmic, programming and implementation issues, as well as experiences gained so far on parallel platforms. Attention is also given to mathematics aspects, notably domain decomposition and scalable algorithms. Topics considered are: basic concepts of parallel computers, parallelization strategies, programming aspects, parallel algorithms, applications in computational fluid dynamics, the present hardware situation and developments to be expected. The book is addressed to students on a graduate level and researchers in industry engaged in scientific computing, who have little or no experience with high performance computing, but who want to learn more, and/or want to port their code to parallel platforms. It is a good starting point for those who want to enter the field of high performance computing, especially if applications in fluid dynamics are envisaged.

These two volumes contain the proceedings of the workshop on the Institute for Computer Instability and Transition, sponsored by Applications in Science and Engineering (ICASE) and the Langley Research Center (LaRC), during May 15 to June 9, 1989. The work shop coincided with the initiation of a new, focused research pro gram on instability and transition at LaRC. The objectives of the workshop were to (i) expose the academic community to current technologically important issues of instability and transition in shear flows over the entire speed range, (ii) acquaint the academic com munity with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these facilities, (iii) review current state-of-the-art and propose fu ture directions for instability and transition research, (iv) accelerate progress in elucidating basic understanding of transition phenomena and in transferring this knowledge into improved design methodolo gies through improved transition modeling, and (v) establish mech anisms for continued interaction. The objectives (i) to (iii) were of course immediately met. It is still premature to assess whether ob jectives (iv) and (v) are achieved. The workshop program consisted of tutorials, research presenta tions, panel discussions, experimental and computational demonstra tions, and collaborative projects.

This study has two declared aims: it presents the theoretical basis for a provably ideal comparative process for relaxing flows (ICP) and jus tifies its application to jet and, in particular, rocket engines. This will be treated in two parts. Part I offers a status quo report on current calculation methods, and compiles and explains briefly the most important data on selected pro minent rocket engines. Starting from the phenomenology of the dynamical and physico-chemical conversion processes in the fuel-oxidizer fluid mixture and in the burned gases, the ideal thermodynamic comparative process is then derived - as a defined sequential change of states in the system. In order to render this comparative process readily under standable, it is first applied to an appropriate model gas using alge braic equations for all relevant parameters. This model gas undergoes energy conversion processes without forfeiting the simplicity of pre sentation typical of classical gas dynamics. Above all, examination of this model offers proof that it is generally impermissible to use, as is done in practice, the familiar isentropic equation for flow changes of state continuously propagated in flow tube theory. Elementary calculations immediately indicate essential attributes which are also typical for relaxing, multicomponent, one-phase systems, such as the significant 'pressure drop phenomenon' or the establishment of the steady mass flow rate as an 'eigenvalue' of the comparative pro cess. Their relevance to the RE theory is stressed."

This volume includes revised and extended versions of selected papers presented at the Tenth International Symposium on Applications of Laser Techniques to Fluid Mechanics held at the Calouste Gulbenkian Foundation in Lisbon, during the period of July 10 to 13, 2000. The papers describe instrumentation developments for Velocity, Scalar and Multi-Phase Flows and results of measurements of Turbulent Flows, and Combustion and Engines. The papers demonstrate the continuing and healthy interest in the development of understanding of new methodologies and implementation in terms of new instrumentation. The prime objective of the Tenth Symposium was to provide a forum for the presentation of the most advanced research on laser techniques for flow measurements, and communicate significant results to fluid mechanics. The application of laser techniques to scientific and engineering fluid flow research was emphasized, but contributions to the theory and practice of laser methods were also considered where they facilitate new improved fluid mechanic research. Attention was placed on laser-Doppler anemometry, particle sizing and other methods for the measurement of velocity and scalars, such as particle image velocimetry and laser induced fluorescence.

This book contains lecture notes and invited contributions presented at the NATO Advanced Study Institute and EPS Liquid State Conference on PHYSICOCHEMICAL HYDRODYNAMICS-PCH: INTERFACIAL PHENOMENA that were held July 1-15, 1986, in LA RABIDA (Huelva) SPAIN. Although we are aware of the difficulty in organizing the contents due to the broad and multidisciplinary aspects of PCH-Interfacial Phenomena, we have tried to accomodate papers by topics and have not followed the order in the presentation at the meetings. There is also no distinction between the ASI notes and Conference papers. We have done our best to offer a coverage as complete as possible of the field. However, we had difficulties coming from the fact that some authors were so busy that either did not find time to submit their contribution or did not have time to write a comprehensive paper. We also had to cope with very late arrivals, postdeadline valuable contributions that we felt had to be included here. Our gratitude goes to the NATO Scientific Affairs Division for its economic support and to the EPS Liquid State Committee for its sponsorship. Financial support also came from Asociacion Industrias Quimicas-Huelva (Spain), Caycit-Ministerio De Educacion Y Ciencia (Spain), Canon-Espana (Spain), Citibank-Espana (Spain), CNLS-Los Alamos Nat. Lab. (U. S. A. ), CSIC (Spain), EPS, ERT (Spain), ESA, Fotonica (Spain), IBM-Espana (Spain), Junta De Andalucia (Spain), NATO, NSF (U. S. A. ), ONR-London (U. S. A.

Dealing with aerodynamics in the broadest sense, this book discusses, in addition to aeroplanes, the aerodynamics of cars and birds, and the motion of diverse objects through air and water. The fundamental notions of mechanics and fluid dynamics are clearly explained, while the underlying science is discussed rigorously, but using only elementary mathematics, and then only occasionally. To put the science into its human context, the author describes -- with many illustrations -- the history of human attempts to fly and discusses the social impact of commercial aviation as well as the outlook for future developments. This new edition has been brought up to date throughout; solutions to selected exercises have been added, as have new problems and other study aids.

The purpose of this volume is to present a clear and systematic account of the mathematical methods of wave phenomena in solids, gases, and water that will be readily accessible to physicists and engineers. The emphasis is on developing the necessary mathematical techniques, and on showing how these mathematical concepts can be effective in unifying the physics of wave propagation in a variety of physical settings: sound and shock waves in gases, water waves, and stress waves in solids. Nonlinear effects and asymptotic phenomena will be discussed. Wave propagation in continuous media (solid, liquid, or gas) has as its foundation the three basic conservation laws of physics: conservation of mass, momentum, and energy, which will be described in various sections of the book in their proper physical setting. These conservation laws are expressed either in the Lagrangian or the Eulerian representation depending on whether the boundaries are relatively fixed or moving. In any case, these laws of physics allow us to derive the "field equations" which are expressed as systems of partial differential equations. For wave propagation phenomena these equations are said to be "hyperbolic" and, in general, nonlinear in the sense of being "quasi linear" . We therefore attempt to determine the properties of a system of "quasi linear hyperbolic" partial differential equations which will allow us to calculate the displacement, velocity fields, etc.

This 2007 book presents a developed general conceptual and basic quantitative analysis as well as the theory of mechanical efficiency of heat engines that a level of ideality and generality compatible with the treatment given to thermal efficiency in classical thermodynamics. This yields broad bearing results concerning the overall cyclic conversion of heat into usable mechanical energy. The work reveals intrinsic limits on the overall performance of reciprocating heat engines. The theory describes the general effects of parameters such as compression ratio and external or buffer pressure on engine output. It also provides rational explanations of certain operational characteristics such as how engines generally behave when supercharged or pressurized. The results also identify optimum geometric configurations for engines operating in various regimes from isothermal to adiabatic and are extended to cover multi-workspace engines and heat pumps. Limited heat transfer due to finite-time effects have also been incorporated into the work.

This booklet is an ideal supplement for any course in thermodynamics or the thermal fluid sciences and a handy reference for the practicing engineer. The tables in the booklet complement and extend the property tables in the appendices to Stephen Turn s Thermodynamics: Concepts and Applications and Thermal-Fluid Sciences: An Integrated Approach. In addition to duplicating the SI tables in these books it extends the tables to cover U.S. Customary units as well. The booklet also contains property data for the refrigerant R-134a and properties of the atmosphere at high altitudes.

Starting from fundamentals of classical stability theory, an overview is given of the transition phenomena in subsonic, wall-bounded shear flows. At first, the consideration focuses on elementary small-amplitude velocity perturbations of laminar shear layers, i.e. instability waves, in the simplest canonical configurations of a plane channel flow and a flat-plate boundary layer. Then the linear stability problem is expanded to include the effects of pressure gradients, flow curvature, boundary-layer separation, wall compliance, etc. related to applications. Beyond the amplification of instability waves is the non-modal growth of local stationary and non-stationary shear flow perturbations which are discussed as well. The volume continues with the key aspect of the transition process, that is, receptivity of convectively unstable shear layers to external perturbations, summarizing main paths of the excitation of laminar flow disturbances. The remainder of the book addresses the instability phenomena found at late stages of transition. These include secondary instabilities and nonlinear features of boundary-layer perturbations that lead to the final breakdown to turbulence. Thus, the reader is provided with a step-by-step approach that covers the milestones and recent advances in the laminar-turbulent transition. Special aspects of instability and transition are discussed through the book and are intended for research scientists, while the main target of the book is the student in the fundamentals of fluid mechanics. Computational guides, recommended exercises, and PowerPoint multimedia notes based on results of real scientific experiments supplement the monograph. These are especially helpful for the neophyte to obtain a solid foundation in hydrodynamic stability. To access the supplementary material go to extras.springer.com and type in the ISBN for this volume.

We are pleased to present the Proceedings of the Second International Conference on Computational Fluid Dynamics held at the University of Sydney, Australia, from July 15 to 19, 2002. The conference was a productive meeting of scientists, mathematicians and engineers involved in the computation of fluid flow. Keynote lectures were presented in the areas of optimisation, algorithms, turbulence and bio-fluid mechanics. Two hundred and fifty abstracts from many countries were received for con sideration. The executive committee, consisting of A. Lerat, M. Napolitano, J.J. Chattot, N. Satofuka and myself, were responsible for the selection of papers. Each of the members had a separate subcommittee to carry out the evaluation. One hundred and seventy papers were selected of which one hundred and fifty two were presented at the conference. All papers that appear in the proceedings have been peer reviewed by a panel of experts (with a minimum of two for every paper) before publication. The conference was attended by 160 delegates with a minimum of late with drawals. The informal and friendly atmosphere provided by the university sur roundings was highly appreciated, and the technical aspects of the conference were stimulating. It is appropriate here to thank Alain Lerat, the retiring secretary of the international scientific committee of the conference. We also wish to welcome J. J. Chattot who is the incoming secretary."

Advanced Transport Phenomena is ideal as a graduate textbook. It contains a detailed discussion of modern analytic methods for the solution of fluid mechanics and heat and mass transfer problems, focusing on approximations based on scaling and asymptotic methods, beginning with the derivation of basic equations and boundary conditions and concluding with linear stability theory. Also covered are unidirectional flows, lubrication and thin-film theory, creeping flows, boundary layer theory, and convective heat and mass transport at high and low Reynolds numbers. The emphasis is on basic physics, scaling and nondimensionalization, and approximations that can be used to obtain solutions that are due either to geometric simplifications, or large or small values of dimensionless parameters. The author emphasizes setting up problems and extracting as much information as possible short of obtaining detailed solutions of differential equations. The book also focuses on the solutions of representative problems. This reflects the book's goal of teaching readers to think about the solution of transport problems.

This volume introduces a systematic approach to the solution of some mathematical problems that arise in the study of the hyperbolic-parabolic systems of equations that govern the motions of thermodynamic fluids. It is intended for a wide audience of theoretical and applied mathematicians with an interest in compressible flow, capillarity theory, and control theory. The focus is particularly on recent results concerning nonlinear asymptotic stability, which are independent of assumptions about the smallness of the initial data. Of particular interest is the loss of control that sometimes results when steady flows of compressible fluids are upset by large disturbances. The main ideas are illustrated in the context of three different physical problems: (i) A barotropic viscous gas in a fixed domain with compact boundary. The domain may be either an exterior domain or a bounded domain, and the boundary may be either impermeable or porous. (ii) An isothermal viscous gas in a domain with free boundaries. (iii) A heat-conducting, viscous polytropic gas.

Thermal Separation Technology is a key discipline for many industries and lays the engineering foundations for the sustainable and economic production of high-quality materials. This book provides fundamental knowledge on this field and may be used both in university teaching and in industrial research and development. Furthermore, it is intended to support professional engineers in their daily efforts to improve plant efficiency and reliability. Previous German editions of this book have gained widespread recognition. This first English edition will now make its content available to the international community of students and professionals. In the first chapters of the book the fundamentals of thermodynamics, heat and mass transfer, and multiphase flow are addressed. Further chapters examine in depth the different unit operations distillation and absorption, extraction, evaporation and condensation, crystallization, adsorption and chromatography, and drying, while the closing chapter provides valuable guidelines for a conceptual process development.

Climate change, environmental impact and declining natural resources are driving scientific research and novel technical solutions. Green Energy and Technology serves as a publishing platform for scientific and technological approaches to "green" - i.e., environmentally friendly and sustainable - technologies. While the main focus lies on energy and power supply, the series also covers green solutions in industrial engineering and engineering design. Green Energy and Technology is a monograph series addressing researchers, advanced students and technical consultants, as well as decision makers in industry and politics. The level presentation ranges from instructional to highly technical.

Small Wind Turbines and its associated software provide a thorough grounding in analysing, designing, building and installing a small wind turbine.

Small turbines are introduced by emphasising their differences from large ones and nearly all the analysis and design examples refer to small turbines. The software provided with the book includes MATLAB programs for power production and starting performance, as well as programs for detailed multi-objective optimisation of blade design. An Excel spreadsheet is provided for applying the simple load model of the IEC standard for small wind turbine safety. Small Wind Turbines and its accompanying software represent the distilled outcome of over twenty years experience in fundamental research, design, installation and field testing of small wind turbines.

Besides being a suitable reference for student projects and detailed design studies, it also provides important background material for engineers and others using small wind turbines for remote power and distributed generation applications.

Current research fields in science and technology were presented and discussed at the EKC2009, informing about the interests and directions of the scientists and engineers in EU countries and Korea. The Conference has emerged from the idea of bringing together EU and Korea to get to know each other better, especially in fields of science and technology.