Academic literature on the topic 'Introductory Diffraction Theory'

We seek to illustrate the inten(t/s)ional ways we tried to create spaces for thinking about paradigms as polyphonic and proliferating. We also share the joyful tensions of this work (hence, inten(t/s)ionalities) and specific pedagogical practices that we believe created a space for students to lean into and explore paradigms not only as a thing but also as a doing—paradigming. Our focus is to discuss (a) how some of Barad’s posthumanist theoretical concepts (e.g., ethico-onto-epistemology and intra-action) became pedagogical inspiration, and (b) through a diffractive reading of data with Barad’s concept of spacetimemattering, we were able to explore what was produced in the course. As we read posthumanist theory, the concepts not only shaped our methodology (i.e., diffractive analysis) but also became pedagogy. A posthumanist paradigm shaped our pedagogical practices as we believe that students are (becoming) qualitative inquirers through a knowing/being/doing in a material world of humans and nonhumans intra-acting.

This textbook is designed for use in a standard physics course on optics at the sophomore level. The book is an attempt to reduce the complexity of coverage found in Modem Optics to allow a student with only elementary calculus to learn the principles of optics and the modern Fourier theory of diffraction and imaging. Examples based on real optics engineering problems are contained in each chapter. Topics covered include aberrations with experimental examples, correction of chromatic aberration, explanation of coherence and the use of interference theory to design an antireflection coating, Fourier transform optics and its application to diffraction and imaging, use of gaussian wave theory, and fiber optics will make the text of interest as a textbook in Electrical and bioengineering as well as Physics. Students who take this course should have completed an introductory physics course and math courses through calculus Need for experience with differential equations is avoided and extensive use of vector theory is avoided by using a one dimensional theory of optics as often as possible. Maxwell’s equations are introduced to determine the properties of a light wave and the boundary conditions are introduced to characterize reflection and refraction. Most discussion is limited to reflection. The book provides an introduction to Fourier transforms. Many pictures, figures, diagrams are used to provide readers a good physical insight of Optics. There are some more difficult topics that could be skipped and they are indicated by boundaries in the text.

The earth receives virtually all of its energy from the sun in the form of electromagnetic radiation. This radiation is absorbed, reflected, and scattered by the earth’s surface, the ocean, and the atmosphere. The absorbed radiation is transformed into heat and other forms of energy, and eventually it is returned to space as low-temperature terrestrial radiation. It is clear that radiation is of fundamental importance to atmosphere-ocean interaction. There exists an adequate body of literature on the subject from an introductory treatment by Fleagle and Businger (1980) to specialized monographs by Kondratjev (1969), Liou (1980), and Goody and Yung (1989). Here it will suffice to introduce the basic concepts and focus on the applications to the air-sea interface. Radiation in the atmosphere and ocean comes from all directions simultaneously. The radiation energy per unit time coming from a specific direction and passing through a unit area perpendicular to that direction is called the radiance, I. The irradiance, Fi, or radiant flux density, is the radiant energy that passes through a unit horizontal area per unit time coming from all directions above it. Therefore where θ is the zenith angle and dω is an infinitesimal solid angle. The cos θ reflects the projection of the horizontal unit area into the direction from where I comes. The limits 0 and 2π of the integral reflect the hemisphere of directions above the unit area. When the radiance is independent of direction it is called isotropic. Equation may then be integrated to yield The irradiance from below the unit area is also called exitance and is denoted by Fe. The net irradiance, Fn, is defined by For isotropic radiance, the net irradiance Fn = 0. The fluxes are positive when upward and negative when downward. The interactions between radiation and matter may take various forms. They include refraction, reflection, scattering, diffraction, absorption, and emission. All these interactions are described by the theory of electromagnetic waves (e.g., Panofsky and Phillips, 1962). The full theory will not be developed here, but a number of basic and useful relations will be introduced to describe the characteristics of the interactions mentioned previously.

This chapter covers the preliminary characterization of the crystals in order to determine if they are suitable for a full structure determination. Probably more frustrating than failure to produce crystals at all, is the growth of beautiful crystals which do not diffract, which have very large unit cell dimensions, or which decay very rapidly in the X-ray beam, though this last problem has been largely overcome by freezing the sample. It is impossible in one brief chapter to give more than a flavour of what the X-ray crystallographic technique entails and it is assumed that the protein chemist growing the crystals will have contact with a protein crystallographer, who will carry out the actual structure determination and in whose laboratory state-of-the-art facilities exist. However, preliminary characterization can often be carried out with little more than the equipment which is widely available in Chemistry and Physics Departments and so the crystal grower remote from a protein crystallography laboratory can monitor the success of their experiments. The reader should refer to the first edition for protocols useful for photographic characterization but such techniques are seldom used nowadays. It must be remembered, in any case, that X-rays are dangerous and the inexperienced should not try to X-ray protein crystals without help. It is necessary to provide an overview of X-ray crystallography, to put the preliminary characterization in context. For a general description of the technique the reader should refer to Glusker et al. (1) or Stout and Jensen (2). For protein crystallography in particular, the books by McRee (3) and Drenth (4) describe many of the advances since the seminal work of Blundell and Johnson (5). Amongst many excellent introductory articles, those by Bragg (6), published years ago, and Glusker (7) are particularly recommended. The scattering or diffraction of X-rays is an interference phenomenon and the interference between the X-rays scattered from the atoms in the structure produces significant changes in the observed diffraction in different directions. This variation in intensity with direction arises because the path differences taken by the scattered X-ray beams are of the same magnitude as the separation of the atoms in the molecule.

The word ‘crystal’ is derived from the Greek root ‘krustallos’ meaning ‘clear ice’. Like ice, crystals are chemically well defined, and many among of them are of transparent and glittering appearance, like quartz, which was for a long time the archetype. Often they are beautiful geometrical solids with regular faces and sharp edges, which probably explains why crystallinity, even in the figurative meaning, is taken as a symbol of perfection and purity. From the physical point of view, crystals are regular three-dimensional arrays of atoms, ions, molecules, or molecular assemblies. Ideal crystals can be imagined as infinite and perfect arrays in which the building blocks (the asymmetric units) are arranged according to well-defined symmetries (forming the 230 space groups) into unit cells that are repeated in the three-dimensions by translations. Experimental crystals, however, have finite dimensions. An implicit consequence is that a macroscopic fragment from a crystal is still a crystal, because the orderly arrangement of molecules within such a fragment still extends at long distances. The practical consequence is that crystal fragments can be used as seeds (Chapter 7). In laboratory-grown crystals the periodicity is never perfect, due to different kinds of local disorders or long-range imperfections like dislocations. Also, these crystals are often of polycrystalline nature. The external forms of crystals are always manifestations of their internal structures and symmetries, even if in some cases these symmetries may be hidden at the macroscopic level, due to differential growth kinetics of the crystal faces. Periodicity in crystal architecture is also reflected in their macroscopic physical properties. The most straightforward example is given by the ability of crystals to diffract X-rays, neutrons, or electrons, the phenomenon underlying structural chemistry and biology (for introductory texts see refs 1 and 2), and the major aim of this book is to present the methods employed to produce three-dimensional crystals of biological macromolecules, but also two-dimensional crystals (Chapter 12), needed for diffraction studies. Other properties of invaluable practical applications should not be overlooked either, as is the case of optical and electronic properties which are at the basis of non-linear optics and modern electronics (for an introduction to physical properties of molecular crystals see ref. 3).

Severe storms have gained more attention in recent years. Improved metocean data have led to new insight into severe wave conditions for marine design. Therefore, there exists an industrial demand for fast and accurate numerical tools to estimate the hydrodynamic loads during e.g. green water events. Model tests generally play an important role in these studies. In the recent past, several practical engineering tools have also been developed, based on the experience from the experimental data bases in combination with simplified but still theoretical formulations. One such tool is Kinema2, which is based on non-linear random wave modeling combined with 3D linear diffraction theory to initially identify green water events, and then finally apply a simplified water-on-deck and slamming load estimation. This forms the background for the work presented in this paper which shows the feasibility of a new technique based on the Smoothed Particle Hydrodynamics (SPH). This method can give more detailed forecast of the hydrodynamics on the deck than the simplified water-on-deck estimation. SPH uses a Lagrangian framework (particles) to describe the fluid dynamics. The water propagation and kinematics of the green water events are, in this introductory stage of the study, reproduced by using a SPH inlet condition where particles are injected with given velocity from a curved rectangular area against the deck and the deckhouse. The relative wave height and water particle velocities found from KINEMA2. Numerical results for water elevation and velocity on deck are compared against model test time series and previous results from other numerical simulation methods. The present Lagrangian nature (compared to traditional Eulerian-VOF methods) can in principe significantly reduce the CPU demand and increase the simulation speed. Slamming pressures can then be calculated e.g. from simple slamming formula calculations. In principle, pressures can also be found directly from the SPH calculations, while this would demand a significantly larger number of particles which increases CPU demand of the SPH method.