This brief epilogue emphasizes that this book is a gateway to new avenues in addressing living matter and new water-based materials.

Early prehistoric accounts of water cycling in nature refer only to, or hint at, the atmospheric phase of the water cycle. Wherever evaporation is alluded to, it is mostly assumed to take place from rivers and the sea. Speculations on the origin of these streams or on whether or how their water returns to where the streams originated, came later in Greek antiquity. This era produced essentially four competing theories on this, namely the seawater filtration theory, the underground condensation theory, the concept of pre-existing underground primal water, likely based on mythology and less accepted by the philosophers, and the rainfall percolation theory. Although the latter contains the essence of our present understanding, it took nearly another 23 centuries before it became the only remaining one to be fully accepted. In recorded history it can be followed as a thread running through the works of the pre-Socratics, the post-Aristotelian Peripatetics, Vitruvius in ancient Rome, Buridan and other medieval Schoolmen, Bartas, Palissy, and Gassendi in the Renaissance, Mariotte, Ray, and Van Musschenbroek at the dawn of modern science, and finally Dalton in the early nineteenth century.

For some purposes, the physical processes relating current runoff to precipitation can best be assumed to take place at the scale of the catchment, without consideration of the detailed subscale processes or for the intricate flow paths inside the watershed. The most common implementation of this idea has been the unit hydrograph (UH), which is based on the assumptions of linearity and stationarity. A UH is characterized by the duration of its precipitation input; this allows the definition of the instantaneous UH, that is the response of a catchment to a delta function precipitation input, or its Green’s function. The UH of a catchment can be identified from available data using the method of least squares. To facilitate the concise parameterization of UH functions for identification and prediction purposes, various conceptualizations have been proposed consisting of different combinations of linear translation elements and linear storage elements. Attempts have been made to extend the UH concept by allowing for nonstationarity and nonlinearities in the response. Long-term streamflow response to mean annual precipitation has also been the subject of many studies.

Master the principles of structural dynamics with this comprehensive and self-contained textbook, with key theoretical concepts explained through real-world engineering applications.

• The theory of natural modes of vibration, the finite element method, and the dynamic response of structures is balanced with practical applications to give students a thorough contextual understanding of the subject.

• Enhanced coverage of damping, rotating systems, and parametric excitation provides students with superior understanding of these essential topics.

• Examples and homework problems, closely linked to real-world applications, enrich and deepen student understanding.

• Curated mathematical appendices equip students with all the tools necessary to excel, without disrupting coverage of core topics.

• Containing all the material needed for a one- or two-semester course, and accompanied online by MATLAB/Python code, this authoritative textbook is the ideal introduction for graduate students in aerospace, mechanical, and civil engineering.

A brief overview and description of the atmospheric lidar measurement technique is followed by the structure of the atmosphere in terms of the troposphere, stratosphere, and mesosphere, as it is usually presented in atmospheric science and meteorology. The atmosphere is then described in terms of lidar observables at all altitudes, including water vapor; trace gases; clouds; several other kinds of particulate matter; and metal atoms, as well as density, temperature, and winds. Examples of lidar measurements include tropospheric and stratospheric ozone, greenhouse gases, other pollutants, tropospheric and stratospheric aerosols, polar stratospheric clouds, and atoms of sodium, potassium, calcium, and iron in the mesosphere. Finally, the structure and contents of the book are described, and suggestions for further reading are given.

This chapter begins with a brief review of electronic circuitry and terminology because optical detection and signal processing are in the realm of electrical engineering. A detailed discussion of analog detection follows, with circuitry including transimpedance amplifiers and equivalent circuits for analyzing noise and bandwidth. Two electronic noise sources are introduced, Johnson noise and amplifier noise, and their effects on SNR are modeled. Photon counting is then discussed in terms of its instrumentation, advantages, and limitations. The basic principles of coherent detection are elucidated through a mathematical derivation, and the advantages of coherent detection are shown: high SNR, optical background discrimination, and the measurement of Doppler shifts to sense winds. The main types of detectors used in lidar systems are then discussed, including intrinsic and PIN photodiodes, photomultipliers, avalanche photodiodes, and single-photon avalanche diodes. The advantages of internal detector gain for optimizing SNR are quantified.

In hydrology it is often necessary to assign a probability to future occurrence of an event of a given magnitude, on the basis of an available record of measurements. While general probability theory provides the basis, over the years some concepts have been developed especially as tools in hydrology. A rough estimate of an event’s nonexceedance probability can be derived from its plotting position in the record; a display of the data on probability graph paper is a useful additional tool. It is often useful to fit a mathematical probability distribution function to the available data, because this provides a succinct description of the data and it allows the formulation of objective confidence criteria. Most probability functions have found application in hydrology. The normal distribution is generally appropriate for long-term averages. The log-gamma (or log-Pearson Type III) distribution is now the preferred function for annual maximal river flows. Several extreme value distributions can describe the smallest and largest extremes of different hydrologic phenomena. Methods have been developed to extend regular data records by inclusion of historical events and by regionalization.

In the analysis of most free-surface flows in hydrology it can be assumed that the pressure distribution is hydrostatic normally to the bottom; this in turn allows the adoption of a uniform velocity profile. These two simplifications form the basis of shallow-water theory. In the resulting continuity and momentum equations, also referred to as the Saint Venant equations, the effects of viscosity and turbulence are parameterized in terms of a friction slope. These equations are not easy to solve in general, but important features of free-surface flow can be brought out by solutions of their linearized, diffusion, quasi-steady-uniform flow (or kinematic wave), and lumped kinematic approximations.

This chapter summarizes the various models to treat isolated uncharged flexible chains and outlines the properties of the chains with a comparison with experimental results. The summary presented in this chapter is the first step to enter into the field of charged macromolecules.

Starting from a general description of model gels and key experimental variables, thermodynamics and swelling equilibria are described. Based on the fundamentals, behaviors of gels under tension, shear, and temperature variation are explained using a combination of theory and experiments. Phase transitions of gels, where volume changes of several orders of magnitude are of common occurrence, are presented in details to enable researchers to design new hydrogels for their intended industrial purpose.