Ted Gest
- Published in print:
- 2001
- Published Online:
- November 2003
- ISBN:
- 9780195103434
- eISBN:
- 9780199833887
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/0195103432.003.0007
- Subject:
- Political Science, American Politics
The federal government asserted a role in fighting narcotics abuse since the early 20th century, but it was not until the Richard Nixon administration starting in 1969 that a federal “war on drugs” ...
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The federal government asserted a role in fighting narcotics abuse since the early 20th century, but it was not until the Richard Nixon administration starting in 1969 that a federal “war on drugs” became high profile. Nixon stressed drives against smuggling heroin from counties like Turkey and Mexico. His administration's efforts were marred by raids on erroneous locations by a new federal Office of Drug Law Enforcement. A successor agency called the ‘Drug Enforcement Administration’ jockeyed with the FBI for supremacy in the drug enforcement field. Drug treatment generally had lower priority when it came to funding. A scourge of “crack” cocaine spread in the mid‐1980s, causing Congress to increase penalties for drug abuse in such a way that black people who primarily used crack were punished much more severely than whites who tended to use cocaine's powder form. An effort to coordinate federal antidrug resources better resulted in the establishment of a White House director of drug control policy (“drug czar”) in 1989; the first to hold the position was former education secretary William Bennett. Drug abuse declined in the 1990s, but there was disagreement over the primary cause. Advocates credited a combination of more‐intense law enforcement, better treatment, and establishment of more than 500 “drug courts” that could ride herd on offenders. The numbers of drug abusers were creeping back up by 1999.Less
The federal government asserted a role in fighting narcotics abuse since the early 20th century, but it was not until the Richard Nixon administration starting in 1969 that a federal “war on drugs” became high profile. Nixon stressed drives against smuggling heroin from counties like Turkey and Mexico. His administration's efforts were marred by raids on erroneous locations by a new federal Office of Drug Law Enforcement. A successor agency called the ‘Drug Enforcement Administration’ jockeyed with the FBI for supremacy in the drug enforcement field. Drug treatment generally had lower priority when it came to funding. A scourge of “crack” cocaine spread in the mid‐1980s, causing Congress to increase penalties for drug abuse in such a way that black people who primarily used crack were punished much more severely than whites who tended to use cocaine's powder form. An effort to coordinate federal antidrug resources better resulted in the establishment of a White House director of drug control policy (“drug czar”) in 1989; the first to hold the position was former education secretary William Bennett. Drug abuse declined in the 1990s, but there was disagreement over the primary cause. Advocates credited a combination of more‐intense law enforcement, better treatment, and establishment of more than 500 “drug courts” that could ride herd on offenders. The numbers of drug abusers were creeping back up by 1999.
Franklin E. Zimring
- Published in print:
- 2006
- Published Online:
- May 2012
- ISBN:
- 9780195181159
- eISBN:
- 9780199944132
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195181159.003.0040
- Subject:
- Sociology, Law, Crime and Deviance
This chapter considers the three theorized causes of crime declines in increasing order of novelty—first police, then the rise and fall of crack cocaine, and finally the impact of increased access to ...
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This chapter considers the three theorized causes of crime declines in increasing order of novelty—first police, then the rise and fall of crack cocaine, and finally the impact of increased access to abortion that, advocates claim, caused a shift in the crime-risk profile of birth cohorts in the 1970s. After an introductory discussion of the definition and special problems of theories that were inspired by the 1990s' decline, unequal attention is given to the three explanations covered. Over half of the chapter addresses the thesis that crime declines in the 1990s were caused by the coming-of-age of population cohorts that were altered by the impact of elective abortion in the United States in the 1970s.Less
This chapter considers the three theorized causes of crime declines in increasing order of novelty—first police, then the rise and fall of crack cocaine, and finally the impact of increased access to abortion that, advocates claim, caused a shift in the crime-risk profile of birth cohorts in the 1970s. After an introductory discussion of the definition and special problems of theories that were inspired by the 1990s' decline, unequal attention is given to the three explanations covered. Over half of the chapter addresses the thesis that crime declines in the 1990s were caused by the coming-of-age of population cohorts that were altered by the impact of elective abortion in the United States in the 1970s.
Bruce C. Bunker and William H. Casey
- Published in print:
- 2016
- Published Online:
- November 2020
- ISBN:
- 9780199384259
- eISBN:
- 9780197562987
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780199384259.003.0024
- Subject:
- Chemistry, Inorganic Chemistry
Although dissolution reactions involving water can etch and decompose oxides, truly catastrophic failures of oxide structures usually involve fractures and ...
More
Although dissolution reactions involving water can etch and decompose oxides, truly catastrophic failures of oxide structures usually involve fractures and mechanical failures. Geologists and geochemists have long recognized that water and ice both play key roles in promoting the fracture and crumbling of rock (see Chapter 17). Freezing and thawing create stresses that amplify the rate at which water attacks metal–oxygen bonds at the crack tip. The interplay between water and stressed oxides also leads to common failures in man-made objects, ranging from the growth of cracks from flaws in windshields to the rupture of optical fibers in communication systems. In this chapter, we outline how mechanical deformations change the reactivity of metal–oxygen bonds with respect to water and other chemicals, and how reactions on strained model compounds have been used to predict time to failure as a function of applied stress. The basic phenomenon of stress corrosion cracking is illustrated in Figure 16.1. Cracks can propagate through oxide materials at extremely fast rates, as anyone who has dropped a wine glass on the floor can attest. High-speed photography reveals that when glass shatters, cracks can spread at speeds of hundreds of meters per second, or half the speed of sound in the glass. At the other end of the spectrum, cracks in glass can grow from preexisting flaws so slowly that only a few chemical bonds are broken at the crack tip per hour. Because mechanical failures are associated with cracking, it is critical for design engineers to understand the factors that control crack growth rates for this enormous range of crack velocities (a factor of 1012). In addition, because it is difficult to measure crack velocities slower than 10−8 m/second, it is often necessary to make major extrapolations from measured data to predict the long-term reliability of glass and ceramic objects. Will an optical fiber under stress fail in 1 year or 10 years? Answering this question can require accurate extrapolations down to crack growth rates as low as 10−10 m/second.
Less
Although dissolution reactions involving water can etch and decompose oxides, truly catastrophic failures of oxide structures usually involve fractures and mechanical failures. Geologists and geochemists have long recognized that water and ice both play key roles in promoting the fracture and crumbling of rock (see Chapter 17). Freezing and thawing create stresses that amplify the rate at which water attacks metal–oxygen bonds at the crack tip. The interplay between water and stressed oxides also leads to common failures in man-made objects, ranging from the growth of cracks from flaws in windshields to the rupture of optical fibers in communication systems. In this chapter, we outline how mechanical deformations change the reactivity of metal–oxygen bonds with respect to water and other chemicals, and how reactions on strained model compounds have been used to predict time to failure as a function of applied stress. The basic phenomenon of stress corrosion cracking is illustrated in Figure 16.1. Cracks can propagate through oxide materials at extremely fast rates, as anyone who has dropped a wine glass on the floor can attest. High-speed photography reveals that when glass shatters, cracks can spread at speeds of hundreds of meters per second, or half the speed of sound in the glass. At the other end of the spectrum, cracks in glass can grow from preexisting flaws so slowly that only a few chemical bonds are broken at the crack tip per hour. Because mechanical failures are associated with cracking, it is critical for design engineers to understand the factors that control crack growth rates for this enormous range of crack velocities (a factor of 1012). In addition, because it is difficult to measure crack velocities slower than 10−8 m/second, it is often necessary to make major extrapolations from measured data to predict the long-term reliability of glass and ceramic objects. Will an optical fiber under stress fail in 1 year or 10 years? Answering this question can require accurate extrapolations down to crack growth rates as low as 10−10 m/second.
Nasr M. Ghoniem and Daniel D. Walgraef
- Published in print:
- 2008
- Published Online:
- May 2008
- ISBN:
- 9780199298686
- eISBN:
- 9780191720222
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199298686.003.0014
- Subject:
- Physics, Condensed Matter Physics / Materials
This chapter begins with a discussion of the causes of the roughening and grooving of solid surfaces. It then discusses Asaro-Tiller surface instability, phase field models, surface patterns caused ...
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This chapter begins with a discussion of the causes of the roughening and grooving of solid surfaces. It then discusses Asaro-Tiller surface instability, phase field models, surface patterns caused by energetic photons and ions, surface stress during rapid heating, stress corrosion cracking, and numerical methods.Less
This chapter begins with a discussion of the causes of the roughening and grooving of solid surfaces. It then discusses Asaro-Tiller surface instability, phase field models, surface patterns caused by energetic photons and ions, surface stress during rapid heating, stress corrosion cracking, and numerical methods.
T. T. C. Ting
- Published in print:
- 1996
- Published Online:
- November 2020
- ISBN:
- 9780195074475
- eISBN:
- 9780197560280
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195074475.003.0014
- Subject:
- Chemistry, Materials Chemistry
A crack, or cracks, in a material is perhaps one of the most studied problems in solid mechanics. This is due to the fact that many structural failures are related to ...
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A crack, or cracks, in a material is perhaps one of the most studied problems in solid mechanics. This is due to the fact that many structural failures are related to the presence of a crack in the material. The knowledge of stress distribution near a crack tip is indispensable in a fracture mechanics analysis (Rice, 1968; Sih and Liebowitz, 1968; Sih and Chen, 1981; Kanninen and Popelar, 1985; K. C. Wu, 1989a). A crack is represented by a slit cut whose surfaces are assumed traction-free. This is a mathematical idealization. For a composite material that consists of stiff short fibers or whiskers in the matrix, we have rigid line inclusions. A rigid line inclusion is the counterpart of a crack. It is sometimes called an anticrack. The displacement at a rigid line inclusion either vanishes or has a rigid body translation and rotation. One of the puzzling problems for a crack is the one when it is located on the x1-axis that is an interface between two dissimilar materials. The displacement of the crack surfaces near the crack tips may oscillate, creating a physically unacceptable phenomenon of interpenetration of two materials. The bimaterial tensor Š introduced in Section 8.8 plays a key role in the analysis. If Š vanishes identically, there is no oscillation. If Š is nonzero, we may decompose the tractions applied on the crack surfaces into two components, one along the right null vector of Š denoted by to and the other on the right eigenplane of Š denoted by tγ . The solution associated with to is not oscillatory. It has the property that the traction on the interface x2=0 is polarized along the right null vector of Š while the crack opening displacement is polarized along the left null vector of Š. The solution associated with tγ is oscillatory. It has the property that the traction on the interface x2=0 is polarized on the right eigenplane of Š while the crack opening displacement is polarized on the left eigenplane of Š.
Less
A crack, or cracks, in a material is perhaps one of the most studied problems in solid mechanics. This is due to the fact that many structural failures are related to the presence of a crack in the material. The knowledge of stress distribution near a crack tip is indispensable in a fracture mechanics analysis (Rice, 1968; Sih and Liebowitz, 1968; Sih and Chen, 1981; Kanninen and Popelar, 1985; K. C. Wu, 1989a). A crack is represented by a slit cut whose surfaces are assumed traction-free. This is a mathematical idealization. For a composite material that consists of stiff short fibers or whiskers in the matrix, we have rigid line inclusions. A rigid line inclusion is the counterpart of a crack. It is sometimes called an anticrack. The displacement at a rigid line inclusion either vanishes or has a rigid body translation and rotation. One of the puzzling problems for a crack is the one when it is located on the x1-axis that is an interface between two dissimilar materials. The displacement of the crack surfaces near the crack tips may oscillate, creating a physically unacceptable phenomenon of interpenetration of two materials. The bimaterial tensor Š introduced in Section 8.8 plays a key role in the analysis. If Š vanishes identically, there is no oscillation. If Š is nonzero, we may decompose the tractions applied on the crack surfaces into two components, one along the right null vector of Š denoted by to and the other on the right eigenplane of Š denoted by tγ . The solution associated with to is not oscillatory. It has the property that the traction on the interface x2=0 is polarized along the right null vector of Š while the crack opening displacement is polarized along the left null vector of Š. The solution associated with tγ is oscillatory. It has the property that the traction on the interface x2=0 is polarized on the right eigenplane of Š while the crack opening displacement is polarized on the left eigenplane of Š.
Adrian P. Sutton
- Published in print:
- 2020
- Published Online:
- August 2020
- ISBN:
- 9780198860785
- eISBN:
- 9780191893001
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198860785.001.0001
- Subject:
- Physics, Condensed Matter Physics / Materials, Crystallography: Physics
Mechanical properties of crystalline materials are almost always dominated by the defects within them. The ability to shape metals into pipes, girders and furniture stems from the generation, motion ...
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Mechanical properties of crystalline materials are almost always dominated by the defects within them. The ability to shape metals into pipes, girders and furniture stems from the generation, motion and interaction of these defects. Defects are also the agents of chemical changes within crystals, enabling mass transport by atomic diffusion and changes of phase. Defects distort the crystal and these distortions enable defects to interact over large distances. The theory of elasticity is used to describe these interactions. Assuming no familiarity with the theory, this book introduces the reader to linear elasticity and its application to point defects, dislocations and cracks. A unique feature of the book is the attention given to the atomic structure of defects and its influence on their properties and their elastic fields. Where it is available brief biographical information is provided about prominent contributors to the field. This textbook is written for postgraduate students in physics, engineering and materials science. It is very likely that even those students with some knowledge of elasticity and defects will find much that is new to them in this book.There are exercises to help the student check their understanding as they work through each chapter. The student is guided through more advanced problems at the end of each chapter. Worked solutions to all exercises and problems are available to course instructors from the OUP website. The last chapter describes four technologically important areas requiring fundamental research, with suggestions for possible PhD projects.Less
Mechanical properties of crystalline materials are almost always dominated by the defects within them. The ability to shape metals into pipes, girders and furniture stems from the generation, motion and interaction of these defects. Defects are also the agents of chemical changes within crystals, enabling mass transport by atomic diffusion and changes of phase. Defects distort the crystal and these distortions enable defects to interact over large distances. The theory of elasticity is used to describe these interactions. Assuming no familiarity with the theory, this book introduces the reader to linear elasticity and its application to point defects, dislocations and cracks. A unique feature of the book is the attention given to the atomic structure of defects and its influence on their properties and their elastic fields. Where it is available brief biographical information is provided about prominent contributors to the field. This textbook is written for postgraduate students in physics, engineering and materials science. It is very likely that even those students with some knowledge of elasticity and defects will find much that is new to them in this book.There are exercises to help the student check their understanding as they work through each chapter. The student is guided through more advanced problems at the end of each chapter. Worked solutions to all exercises and problems are available to course instructors from the OUP website. The last chapter describes four technologically important areas requiring fundamental research, with suggestions for possible PhD projects.
Habib Ammari, Elie Bretin, Josselin Garnier, Hyeonbae Kang, Hyundae Lee, and Abdul Wahab
- Published in print:
- 2015
- Published Online:
- October 2017
- ISBN:
- 9780691165318
- eISBN:
- 9781400866625
- Item type:
- book
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691165318.001.0001
- Subject:
- Mathematics, Applied Mathematics
This book comprehensively explores elasticity imaging and examines recent, important developments in asymptotic imaging, modeling, and analysis of deterministic and stochastic elastic wave ...
More
This book comprehensively explores elasticity imaging and examines recent, important developments in asymptotic imaging, modeling, and analysis of deterministic and stochastic elastic wave propagation phenomena. It derives the best possible functional images for small inclusions and cracks within the context of stability and resolution, and introduces a topological derivative-based imaging framework for detecting elastic inclusions in the time-harmonic regime. For imaging extended elastic inclusions, accurate optimal control methodologies are designed and the effects of uncertainties of the geometric or physical parameters on stability and resolution properties are evaluated. In particular, the book shows how localized damage to a mechanical structure affects its dynamic characteristics, and how measured eigenparameters are linked to elastic inclusion or crack location, orientation, and size. Demonstrating a novel method for identifying, locating, and estimating inclusions and cracks in elastic structures, the book opens possibilities for a mathematical and numerical framework for elasticity imaging of nanoparticles and cellular structures.Less
This book comprehensively explores elasticity imaging and examines recent, important developments in asymptotic imaging, modeling, and analysis of deterministic and stochastic elastic wave propagation phenomena. It derives the best possible functional images for small inclusions and cracks within the context of stability and resolution, and introduces a topological derivative-based imaging framework for detecting elastic inclusions in the time-harmonic regime. For imaging extended elastic inclusions, accurate optimal control methodologies are designed and the effects of uncertainties of the geometric or physical parameters on stability and resolution properties are evaluated. In particular, the book shows how localized damage to a mechanical structure affects its dynamic characteristics, and how measured eigenparameters are linked to elastic inclusion or crack location, orientation, and size. Demonstrating a novel method for identifying, locating, and estimating inclusions and cracks in elastic structures, the book opens possibilities for a mathematical and numerical framework for elasticity imaging of nanoparticles and cellular structures.
Andrew Briggs and Oleg Kolosov
- Published in print:
- 2009
- Published Online:
- February 2010
- ISBN:
- 9780199232734
- eISBN:
- 9780191716355
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199232734.001.0001
- Subject:
- Physics, Condensed Matter Physics / Materials
Acoustic microscopy enables you to image and measure the elastic properties of materials with the resolution of a good microscope. By using frequencies in the microwave range, it is possible to make ...
More
Acoustic microscopy enables you to image and measure the elastic properties of materials with the resolution of a good microscope. By using frequencies in the microwave range, it is possible to make the acoustic wavelength comparable with the wavelength of light, and hence to achieve a resolution comparable with an optical microscope. The contrast gives information about the elastic properties and structure of the sample. Since acoustic waves can propagate in materials, acoustic microscopy can be used for interior imaging, with high sensitivity to defects such as delaminations. Solids can support both longitudinal and transverse acoustic waves. At surfaces a combination of the two known as Rayleigh waves can propagate, and in many circumstances these dominate the contrast in acoustic microscopy. Contrast theory accounts for the variation of signal with defocus, V(z). Acoustic microscopy can image and measure properties such as anisotropy and features such as surface boundaries and cracks. A scanning probe microscope can be used to detect ultrasonic vibration of a surface with resolution in the nanometre range, thus beating the diffraction limit by operating in the extreme near‐field. This 2nd edition of Acoustic Microscopy has a major new chapter on the technique and applications of acoustically exited probe microscopy.Less
Acoustic microscopy enables you to image and measure the elastic properties of materials with the resolution of a good microscope. By using frequencies in the microwave range, it is possible to make the acoustic wavelength comparable with the wavelength of light, and hence to achieve a resolution comparable with an optical microscope. The contrast gives information about the elastic properties and structure of the sample. Since acoustic waves can propagate in materials, acoustic microscopy can be used for interior imaging, with high sensitivity to defects such as delaminations. Solids can support both longitudinal and transverse acoustic waves. At surfaces a combination of the two known as Rayleigh waves can propagate, and in many circumstances these dominate the contrast in acoustic microscopy. Contrast theory accounts for the variation of signal with defocus, V(z). Acoustic microscopy can image and measure properties such as anisotropy and features such as surface boundaries and cracks. A scanning probe microscope can be used to detect ultrasonic vibration of a surface with resolution in the nanometre range, thus beating the diffraction limit by operating in the extreme near‐field. This 2nd edition of Acoustic Microscopy has a major new chapter on the technique and applications of acoustically exited probe microscopy.
Adrian P. Sutton
- Published in print:
- 2020
- Published Online:
- August 2020
- ISBN:
- 9780198860785
- eISBN:
- 9780191893001
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198860785.003.0009
- Subject:
- Physics, Condensed Matter Physics / Materials, Crystallography: Physics
Loaded slit cracks are modelled as continuous distributions of dislocations with infinitesimal Burgers vectors. Cauchy-type singular integral equations for the density of Burgers vector in these ...
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Loaded slit cracks are modelled as continuous distributions of dislocations with infinitesimal Burgers vectors. Cauchy-type singular integral equations for the density of Burgers vector in these distributions are solved using the theory of Chebyshev polynomials. The elastic fields of mode I elastic slit cracks are derived and the stress intensity factor is defined. Other defects may interact with cracks such as dislocations. This leads to the concepts of shielding and anti-shielding of cracks by dislocations. The Dugdale–Bilby–Cottrell–Swinden model of a mode I crack completely shielded by a plastic zone is derived. By introducing a dislocation free zone between the plastic zone and the crack tip the crack tip is only partially shielded, enabling more brittle tendencies to be described. Griffith’s energy criterion for the growth of an existing crack is seen as necessary but not sufficient. The Barenblatt crack introduces the influence of interatomic forces at the crack tip.Less
Loaded slit cracks are modelled as continuous distributions of dislocations with infinitesimal Burgers vectors. Cauchy-type singular integral equations for the density of Burgers vector in these distributions are solved using the theory of Chebyshev polynomials. The elastic fields of mode I elastic slit cracks are derived and the stress intensity factor is defined. Other defects may interact with cracks such as dislocations. This leads to the concepts of shielding and anti-shielding of cracks by dislocations. The Dugdale–Bilby–Cottrell–Swinden model of a mode I crack completely shielded by a plastic zone is derived. By introducing a dislocation free zone between the plastic zone and the crack tip the crack tip is only partially shielded, enabling more brittle tendencies to be described. Griffith’s energy criterion for the growth of an existing crack is seen as necessary but not sufficient. The Barenblatt crack introduces the influence of interatomic forces at the crack tip.
G. A. D. Briggs and O. V. Kolosov
- Published in print:
- 2009
- Published Online:
- February 2010
- ISBN:
- 9780199232734
- eISBN:
- 9780191716355
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199232734.003.0012
- Subject:
- Physics, Condensed Matter Physics / Materials
Surface cracks and boundaries give contrast in acoustic microscopy even when they are so fine that by conventional resolution criteria they would be expected to be scarcely visible. The contrast ...
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Surface cracks and boundaries give contrast in acoustic microscopy even when they are so fine that by conventional resolution criteria they would be expected to be scarcely visible. The contrast arises from the scattering of Rayleigh waves, and the evidence for this is the tell‐tale presence of fringes parallel to cracks, with spacing equal to half a Rayleigh wavelength. Contrast theory based on separating the specular and Rayleigh components of the signal give a good account of the fringes which are observed. Time‐resolved measurements can be made of crack‐tip diffracted signals. The remarkable contrast from cracks is useful in the study of indentation and fracture of low‐ductility materials.Less
Surface cracks and boundaries give contrast in acoustic microscopy even when they are so fine that by conventional resolution criteria they would be expected to be scarcely visible. The contrast arises from the scattering of Rayleigh waves, and the evidence for this is the tell‐tale presence of fringes parallel to cracks, with spacing equal to half a Rayleigh wavelength. Contrast theory based on separating the specular and Rayleigh components of the signal give a good account of the fringes which are observed. Time‐resolved measurements can be made of crack‐tip diffracted signals. The remarkable contrast from cracks is useful in the study of indentation and fracture of low‐ductility materials.
Victor F. Petrenko and Robert W. Whitworth
- Published in print:
- 2002
- Published Online:
- February 2010
- ISBN:
- 9780198518945
- eISBN:
- 9780191707247
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198518945.003.0008
- Subject:
- Physics, Crystallography: Physics
Ice is a material that exhibits both ductile flow, as in the flow of a glacier, and also brittle fracture, as in the crushing of ice under impact from an icebreaker. This chapter considers ...
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Ice is a material that exhibits both ductile flow, as in the flow of a glacier, and also brittle fracture, as in the crushing of ice under impact from an icebreaker. This chapter considers laboratory-scale experiments on the deformation of single crystals and of polycrystalline ice and their interpretation. Creep of single crystals occurs by the glide and multiplication of dislocations on the basal plane and is thus highly anisotropic. In polycrystalline specimens deformed under constant load the creep accelerates, reaches a steady state and finally accelerates again. The deformation of individual grains is confined by those around them, and large stresses build up which may be relieved by diffusion or by cracking. The theory of fracture involves both the nucleation of cracks and their propagation.Less
Ice is a material that exhibits both ductile flow, as in the flow of a glacier, and also brittle fracture, as in the crushing of ice under impact from an icebreaker. This chapter considers laboratory-scale experiments on the deformation of single crystals and of polycrystalline ice and their interpretation. Creep of single crystals occurs by the glide and multiplication of dislocations on the basal plane and is thus highly anisotropic. In polycrystalline specimens deformed under constant load the creep accelerates, reaches a steady state and finally accelerates again. The deformation of individual grains is confined by those around them, and large stresses build up which may be relieved by diffusion or by cracking. The theory of fracture involves both the nucleation of cracks and their propagation.
Habib Ammari, Elie Bretin, Josselin Garnier, Hyeonbae Kang, Hyundae Lee, and Abdul Wahab
- Published in print:
- 2015
- Published Online:
- October 2017
- ISBN:
- 9780691165318
- eISBN:
- 9781400866625
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691165318.003.0001
- Subject:
- Mathematics, Applied Mathematics
This book is about recent mathematical, numerical and statistical approaches for elasticity imaging of inclusions and cracks with waves at zero, single or multiple non-zero frequencies. It considers ...
More
This book is about recent mathematical, numerical and statistical approaches for elasticity imaging of inclusions and cracks with waves at zero, single or multiple non-zero frequencies. It considers important developments in asymptotic imaging, stochastic modeling, and analysis of both deterministic and stochastic elastic wave propagation phenomena and puts them together in a coherent way. It gives emphasis on deriving the best possible imaging functionals for small inclusions and cracks in the sense of stability and resolution. For imaging extended elastic inclusions, the book develops accurate optimal control methodologies and examines the effect of uncertainties of the geometric or physical parameters on their stability and resolution properties. It also presents an asymptotic framework for vibration testing and a method for identifying, locating, and estimating inclusions and cracks in elastic structures by measuring their modal characteristics.Less
This book is about recent mathematical, numerical and statistical approaches for elasticity imaging of inclusions and cracks with waves at zero, single or multiple non-zero frequencies. It considers important developments in asymptotic imaging, stochastic modeling, and analysis of both deterministic and stochastic elastic wave propagation phenomena and puts them together in a coherent way. It gives emphasis on deriving the best possible imaging functionals for small inclusions and cracks in the sense of stability and resolution. For imaging extended elastic inclusions, the book develops accurate optimal control methodologies and examines the effect of uncertainties of the geometric or physical parameters on their stability and resolution properties. It also presents an asymptotic framework for vibration testing and a method for identifying, locating, and estimating inclusions and cracks in elastic structures by measuring their modal characteristics.
Dimitri A. Bogazianos
- Published in print:
- 2011
- Published Online:
- March 2016
- ISBN:
- 9780814787007
- eISBN:
- 9780814725160
- Item type:
- chapter
- Publisher:
- NYU Press
- DOI:
- 10.18574/nyu/9780814787007.003.0002
- Subject:
- Sociology, Law, Crime and Deviance
This chapter examines rap's unique expressive position in relation to the primary contradictions of crack cocaine's punishment structure as well as recent arguments condemning this structure, ...
More
This chapter examines rap's unique expressive position in relation to the primary contradictions of crack cocaine's punishment structure as well as recent arguments condemning this structure, including those from the U.S. Supreme Court and the U.S. Sentencing Commission. After discussing the contradictory policy contexts out of which crack's lethal logic of work eventually emerged, the chapter considers the “punitive turn” in U.S. crime-control policy and the “scholarly near misses” that have influenced analyses of the rap–crack connection. It suggests ways of rethinking the rap–crack connection in order to move beyond reductionist accounts in which rap and inner-city communities are taken as mere reflections of each other.Less
This chapter examines rap's unique expressive position in relation to the primary contradictions of crack cocaine's punishment structure as well as recent arguments condemning this structure, including those from the U.S. Supreme Court and the U.S. Sentencing Commission. After discussing the contradictory policy contexts out of which crack's lethal logic of work eventually emerged, the chapter considers the “punitive turn” in U.S. crime-control policy and the “scholarly near misses” that have influenced analyses of the rap–crack connection. It suggests ways of rethinking the rap–crack connection in order to move beyond reductionist accounts in which rap and inner-city communities are taken as mere reflections of each other.
Dimitri A. Bogazianos
- Published in print:
- 2011
- Published Online:
- March 2016
- ISBN:
- 9780814787007
- eISBN:
- 9780814725160
- Item type:
- chapter
- Publisher:
- NYU Press
- DOI:
- 10.18574/nyu/9780814787007.003.0003
- Subject:
- Sociology, Law, Crime and Deviance
This chapter examines the cultural resonance between rap and crack cocaine by focusing on the complicated sociolegal logics that paved the way for the drug's lethal effects, and out of which its ...
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This chapter examines the cultural resonance between rap and crack cocaine by focusing on the complicated sociolegal logics that paved the way for the drug's lethal effects, and out of which its symbolic power developed. It first considers the law and policy on crack, including the bill signed by President Barack Obama in August 2010 repealing the mandatory minimum for the simple possession of crack and reducing the sentencing disparity between crack trafficking and powder trafficking from 100-to-1 to 18-to-1. It then traces the history of the paradoxical punishment of crack cocaine, arguing that the 100-to-1 sentencing disparity between powder and crack was deliberately and intentionally created. It also discusses the link between the 100-to-1 sentencing disparity and the so-called “Kingpin Strategy,” along with the violence that came to be associated with crack's low-level distribution system. Finally, the chapter explores the broad consensus among researchers that the lethal violence of the crack era was a product of the systemic features of crack markets themselves.Less
This chapter examines the cultural resonance between rap and crack cocaine by focusing on the complicated sociolegal logics that paved the way for the drug's lethal effects, and out of which its symbolic power developed. It first considers the law and policy on crack, including the bill signed by President Barack Obama in August 2010 repealing the mandatory minimum for the simple possession of crack and reducing the sentencing disparity between crack trafficking and powder trafficking from 100-to-1 to 18-to-1. It then traces the history of the paradoxical punishment of crack cocaine, arguing that the 100-to-1 sentencing disparity between powder and crack was deliberately and intentionally created. It also discusses the link between the 100-to-1 sentencing disparity and the so-called “Kingpin Strategy,” along with the violence that came to be associated with crack's low-level distribution system. Finally, the chapter explores the broad consensus among researchers that the lethal violence of the crack era was a product of the systemic features of crack markets themselves.
Elissa Marder
- Published in print:
- 2012
- Published Online:
- May 2012
- ISBN:
- 9780823240555
- eISBN:
- 9780823240593
- Item type:
- chapter
- Publisher:
- Fordham University Press
- DOI:
- 10.5422/fordham/9780823240555.003.0007
- Subject:
- Literature, Criticism/Theory
This chapter explores the relationship between technology, politics, and the maternal function by looking at Avital Ronell's important work on the telephone as a fantastic, fetishistic extension of ...
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This chapter explores the relationship between technology, politics, and the maternal function by looking at Avital Ronell's important work on the telephone as a fantastic, fetishistic extension of the maternal body in The Telephone Book. It takes up Ronell's provocative claim that investment in a certain repressive concept of the mother (as the grounding and stable incarnation of “nature,” “origin,” “connection,” “meaning,” “presence,” and “life”) is one of the critical sources of the technological drive. Moreover, because (as Ronell points out) the technological drive is most often linked to an attempt to deny the reality of the body's vulnerability and mortality by replacing (or supplementing) it with a body that does not know death, the driving fantasy of technology is the (re)production of a prosthetic maternal body which would be capable of procreating and incarnating this “pure life.” But “pure life” resembles death more than it does “life” as it privileges preservation, immobility, and absolute resistance to change or difference. Consequently, the prosthetic maternal body is an inherently monstrous and repressive figure.Less
This chapter explores the relationship between technology, politics, and the maternal function by looking at Avital Ronell's important work on the telephone as a fantastic, fetishistic extension of the maternal body in The Telephone Book. It takes up Ronell's provocative claim that investment in a certain repressive concept of the mother (as the grounding and stable incarnation of “nature,” “origin,” “connection,” “meaning,” “presence,” and “life”) is one of the critical sources of the technological drive. Moreover, because (as Ronell points out) the technological drive is most often linked to an attempt to deny the reality of the body's vulnerability and mortality by replacing (or supplementing) it with a body that does not know death, the driving fantasy of technology is the (re)production of a prosthetic maternal body which would be capable of procreating and incarnating this “pure life.” But “pure life” resembles death more than it does “life” as it privileges preservation, immobility, and absolute resistance to change or difference. Consequently, the prosthetic maternal body is an inherently monstrous and repressive figure.
Francois Louchet
- Published in print:
- 2020
- Published Online:
- December 2020
- ISBN:
- 9780198866930
- eISBN:
- 9780191903854
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198866930.003.0001
- Subject:
- Physics, Geophysics, Atmospheric and Environmental Physics
The chapter gives the etymology of the word “avalanche”. It defines the various types of snow avalanches, as slab, full-depth or loose snow, dense or airborne-powder, spontaneous or artificial ones. ...
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The chapter gives the etymology of the word “avalanche”. It defines the various types of snow avalanches, as slab, full-depth or loose snow, dense or airborne-powder, spontaneous or artificial ones. It also mentions the fact that other materials, such as sand, rock-falls, and landslides, may behave in a similar way, as developed in chapter 4. It also aims at making clear a number of idioms often used in this field. The content of each of the book chapters is also summarized.Less
The chapter gives the etymology of the word “avalanche”. It defines the various types of snow avalanches, as slab, full-depth or loose snow, dense or airborne-powder, spontaneous or artificial ones. It also mentions the fact that other materials, such as sand, rock-falls, and landslides, may behave in a similar way, as developed in chapter 4. It also aims at making clear a number of idioms often used in this field. The content of each of the book chapters is also summarized.
Dimitri A. Bogazianos
- Published in print:
- 2011
- Published Online:
- March 2016
- ISBN:
- 9780814787007
- eISBN:
- 9780814725160
- Item type:
- chapter
- Publisher:
- NYU Press
- DOI:
- 10.18574/nyu/9780814787007.003.0001
- Subject:
- Sociology, Law, Crime and Deviance
This introductory chapter explains that the book explores the ways in which rap expresses one of the most powerful symbols of America's paradoxical crime policy: the 100-to-1 sentencing disparity ...
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This introductory chapter explains that the book explores the ways in which rap expresses one of the most powerful symbols of America's paradoxical crime policy: the 100-to-1 sentencing disparity between crack cocaine and powder whereby someone convicted of “simply” possessing five grams of crack had been required by law to serve no less than five years in prison. Drawing on the author's personal experiences with rap and crack, the book examines the degree to which crack cocaine emerged as a primary symbolic referent through the development of an important reflexive lyrical stance that many rap artists in the 1990s took toward their own commercialization. It discusses the cultural consequences of crack's paradoxical punishment, focusing on a reflexive lyrical stance that emerged in 1990s New York rap, which critiqued the music industry for being corrupt, unjust, and criminal. The book also considers how rappers began drawing parallels between the “rap game” and the “crack game,” juxtaposing their own exploits in street crime with the machinations of industry executives.Less
This introductory chapter explains that the book explores the ways in which rap expresses one of the most powerful symbols of America's paradoxical crime policy: the 100-to-1 sentencing disparity between crack cocaine and powder whereby someone convicted of “simply” possessing five grams of crack had been required by law to serve no less than five years in prison. Drawing on the author's personal experiences with rap and crack, the book examines the degree to which crack cocaine emerged as a primary symbolic referent through the development of an important reflexive lyrical stance that many rap artists in the 1990s took toward their own commercialization. It discusses the cultural consequences of crack's paradoxical punishment, focusing on a reflexive lyrical stance that emerged in 1990s New York rap, which critiqued the music industry for being corrupt, unjust, and criminal. The book also considers how rappers began drawing parallels between the “rap game” and the “crack game,” juxtaposing their own exploits in street crime with the machinations of industry executives.
T. T. C. Ting
- Published in print:
- 1996
- Published Online:
- November 2020
- ISBN:
- 9780195074475
- eISBN:
- 9780197560280
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195074475.003.0006
- Subject:
- Chemistry, Materials Chemistry
As a starter for anisotropic elastostatics we study special two-dimensional deformations of anisotropic elastic bodies, namely, antiplane deformations. Not all ...
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As a starter for anisotropic elastostatics we study special two-dimensional deformations of anisotropic elastic bodies, namely, antiplane deformations. Not all anisotropic elastic materials are capable of an antiplane deformation. When they are, the inplane displacement and the antiplane displacement are uncoupled. The deformations due to inplane displacement are plane strain deformations. Associated with plane strain deformations are plane stress deformations. After defining these special deformations in Sections 3.1 and 3.2 we present some basic solutions of antiplane deformations. They provide useful references for more general deformations we will study in Chapters 8, 10, and 11. The derivation and motivation in solving more general deformations in those chapters become more transparent if the reader reads this chapter first. The solutions obtained in those chapters reduce to the solutions presented here when the materials are restricted to special materials and the deformations are limited to antiplane deformations. In a fixed rectangular coordinate system xi (i=1, 2, 3), let ui, σij, and εij be the displacement, stress, and strain, respectively. The strain-displacement relations and the equations of equilibrium are . . .εij = 1/2 (ui,j + uj,i),. . . . . . (3.1 -1) . . . . . .σij,j =0,. . . . . . (3.1 - 2). . . in which repeated indices imply summation and a comma stands for differentiation. The stress-strain laws for an anisotropic elastic material can be written as σij = Cijks εks or εij = Sijksσks, . . .(3.1 - 3). . . where Cijks and Sijks are, respectively, the elastic stiffnesses and
compliances.
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As a starter for anisotropic elastostatics we study special two-dimensional deformations of anisotropic elastic bodies, namely, antiplane deformations. Not all anisotropic elastic materials are capable of an antiplane deformation. When they are, the inplane displacement and the antiplane displacement are uncoupled. The deformations due to inplane displacement are plane strain deformations. Associated with plane strain deformations are plane stress deformations. After defining these special deformations in Sections 3.1 and 3.2 we present some basic solutions of antiplane deformations. They provide useful references for more general deformations we will study in Chapters 8, 10, and 11. The derivation and motivation in solving more general deformations in those chapters become more transparent if the reader reads this chapter first. The solutions obtained in those chapters reduce to the solutions presented here when the materials are restricted to special materials and the deformations are limited to antiplane deformations. In a fixed rectangular coordinate system xi (i=1, 2, 3), let ui, σij, and εij be the displacement, stress, and strain, respectively. The strain-displacement relations and the equations of equilibrium are . . .εij = 1/2 (ui,j + uj,i),. . . . . . (3.1 -1) . . . . . .σij,j =0,. . . . . . (3.1 - 2). . . in which repeated indices imply summation and a comma stands for differentiation. The stress-strain laws for an anisotropic elastic material can be written as σij = Cijks εks or εij = Sijksσks, . . .(3.1 - 3). . . where Cijks and Sijks are, respectively, the elastic stiffnesses and
compliances.
T. T. C. Ting
- Published in print:
- 1996
- Published Online:
- November 2020
- ISBN:
- 9780195074475
- eISBN:
- 9780197560280
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195074475.003.0012
- Subject:
- Chemistry, Materials Chemistry
Not all boundary value problems are amenable to a simple analytical solution. This is particularly the case when the geometry of the boundary on which the boundary ...
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Not all boundary value problems are amenable to a simple analytical solution. This is particularly the case when the geometry of the boundary on which the boundary conditions are specified contains a corner. A crack tip is a special corner. When an analytical solution for the entire region is not available, asymptotic solutions near the corner can be obtained which provide useful information on the nature of stress singularities at the corner. They also provide more accurate numerical solutions by a finite element scheme in which the asymptotic solution at the corner is employed in a special element at the corner with regular elements elsewhere (see, for example, Stolarski and Chiang, 1989). Other information that can be obtained by an asymptotic analysis is the decay factor of stress at a large distance from a point at which a self-equilibrated load is applied (Crafter, et al., 1993). For singularities that arise in non-linear elastic materials the reader is referred to the book by Antman (1995). As in Chapter 8 most solutions can be expressed in a real form with the aid of identities presented in Chapters 6 and 7.
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Not all boundary value problems are amenable to a simple analytical solution. This is particularly the case when the geometry of the boundary on which the boundary conditions are specified contains a corner. A crack tip is a special corner. When an analytical solution for the entire region is not available, asymptotic solutions near the corner can be obtained which provide useful information on the nature of stress singularities at the corner. They also provide more accurate numerical solutions by a finite element scheme in which the asymptotic solution at the corner is employed in a special element at the corner with regular elements elsewhere (see, for example, Stolarski and Chiang, 1989). Other information that can be obtained by an asymptotic analysis is the decay factor of stress at a large distance from a point at which a self-equilibrated load is applied (Crafter, et al., 1993). For singularities that arise in non-linear elastic materials the reader is referred to the book by Antman (1995). As in Chapter 8 most solutions can be expressed in a real form with the aid of identities presented in Chapters 6 and 7.
Robert B. Jackson
- Published in print:
- 2002
- Published Online:
- October 2013
- ISBN:
- 9780300088564
- eISBN:
- 9780300129519
- Item type:
- chapter
- Publisher:
- Yale University Press
- DOI:
- 10.12987/yale/9780300088564.003.0003
- Subject:
- History, Ancient History / Archaeology
This chapter explains that from the site of Mons Claudianus, which lies 50 kilometers south of Gebel Dokhan, the Romans hewed the enormous columns of speckled, white granite which were to grace some ...
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This chapter explains that from the site of Mons Claudianus, which lies 50 kilometers south of Gebel Dokhan, the Romans hewed the enormous columns of speckled, white granite which were to grace some of the most splendid buildings of Roman antiquity, among them Trajan's Forum and the Pantheon itself. There are approximately 130 quarries in the hills surrounding Mons Claudianus, many of which contain examples of the variety of objects the Romans fashioned from the fine stone but discarded because of cracks or other defects. Recent discoveries indicate that at some point during its occupation, as many as 920 people lived at Mons Claudianus. Scholars do not know exactly when or why quarrying ceased there. The archaeological research at Mons Claudianus itself is becoming increasingly difficult because the site is threatened by modern quarrying, which every year destroys valuable inscriptions in the surrounding area.Less
This chapter explains that from the site of Mons Claudianus, which lies 50 kilometers south of Gebel Dokhan, the Romans hewed the enormous columns of speckled, white granite which were to grace some of the most splendid buildings of Roman antiquity, among them Trajan's Forum and the Pantheon itself. There are approximately 130 quarries in the hills surrounding Mons Claudianus, many of which contain examples of the variety of objects the Romans fashioned from the fine stone but discarded because of cracks or other defects. Recent discoveries indicate that at some point during its occupation, as many as 920 people lived at Mons Claudianus. Scholars do not know exactly when or why quarrying ceased there. The archaeological research at Mons Claudianus itself is becoming increasingly difficult because the site is threatened by modern quarrying, which every year destroys valuable inscriptions in the surrounding area.