2,384 research outputs found
Slaves’ Supplicant & Slaves’ Triumphant: The Middle Passage of an Abolitionist Icon
No full textIn chapter 11, Jeffrey R. Kerr-Ritchie’s “Slaves Supplicant and Slaves Triumphant: The Middle Passage of an Abolitionist Icon” proposes an alternative dialectic between the kneeling slave image and postabolition representations of former slaves at various times and places all over the Atlantic world. The chapter examines a transition in the visual representation of the slave from the beseeching captive to the grateful ex-slave. Kerr-Ritchie argues that the popular visual image of slave supplication was crucial in constructing the metaphorical image of ex-slaves’ gratitude for their freedom. Even though visual depictions of heroic and triumphant slaves also exist—challenging the more troubling images of supplicant and grateful slaves—representations of enslaved men and women as passive victims are still disseminated via websites, textbooks, scholarly book covers, academic journal covers, conference posters, and public monuments. Through a well-studied genealogy of the images of supplicant, grateful, and triumphant slaves, this chapter deepens readers’ understanding of the Atlantic visual culture of slavery
Freedom\u27s Seekers: Essays on Comparative Emancipation
No full textJeffery R. Kerr-Ritchie’s Freedom’s Seekers offers a bold and innovative intervention into the study of emancipation as a transnational phe-nomenon and serves as an important contribution to our understanding of the remaking of the nineteenth-century Atlantic Americas. Drawing on decades of research into slave and emancipation societies, Kerr-Ritchie is attentive to those who sought but were not granted freedom, and those who resisted enslavement individually as well as collectively on behalf of their communities. He explores the many roles that fugitive slaves, slave soldiers, and slave rebels played in their own societies. He likewise explicates the lives of individual freedmen, freedwomen, and freed children to show how the first free-born generation helped shape the terms and conditions of the post-slavery world. Freedom’s Seekers is a signal contribution to African Diaspora studies, especially in its rigorous respect for the agency of those who sought and then fought for their freedom, and its consistent attention to the transnational dimensions of emancipation
Rites of August First: Emancipation Day in the Black Atlantic World
No full textThirty years before Lincoln issued the Emancipation Proclamation, the antislavery movement won its first victory in the British Parliament. On August 1, 1834, the Abolition of Slavery Bill took effect, ending colonial slavery throughout the British Empire. Over the next three decades, August First Day, also known as West India Day and Emancipation Day, became the most important annual celebration of emancipation among people of African descent in the northern United States, the British Caribbean, Canada West, and the United Kingdom and played a critical role in popular mobilization against American slavery. In Rites of August First, J. R. KerrRitchie provides the first detailed analysis of the origins, nature, and consequences of this important commemoration that helped to shape the age of AngloAmerican emancipation. Combining social, cultural, and political history, KerrRitchie discusses the ideological and cultural representations of August First Day in print, oratory, and visual images. Spanning the Western hemisphere, Kerr Ritchie successfully unravels the cultural politics of emancipation celebrations, analyzing the social practices informed by public ritual, symbol, and spectacle designed to elicit feelings of common identity among blacks in the Atlantic World. Rites of August First shows how and why the commemorative events changed between British emancipation and the freeing of slaves in the United States a generation later, while also examining the connections among local, regional, and international commemorations. While shedding light on an important black institution that has been long ignored, Rites of August First also contributes to the broader study of emancipation and black Atlantic identity. Its transnational approach challenges local and national narratives that have largely shaped previous investigations of these questions. KerrRitchie shows how culture and community were truly political at this important historical moment and, most broadly, how politics and culture converge and profoundly influence each other
Was U.S. Emancipation Exceptional in the Atlantic, or Other Worlds?
No full textA refreshing and intriguing interdisciplinary examination of the ways in which the history and cultures of the American South have been largely shaped by forces beyond the geographical boundaries of the United States. --Allison Graham, author of Framing the South This is an impressive collection of essays, reflective of the latest theoretical interpretations that illuminate how scholars are looking anew at local stories within a global context. --Glenn T. Eskew, author of But for Birmingham While much research on the American South considers the region in terms of its relationship with the North, emphasizing black and white racial binaries and outdated geographical boundaries, The American South and the Atlantic World seeks larger thematic and spatial contexts. This is the first book to focus explicitly on how contacts with the peoples, cultures, ideas, and economies of the Atlantic World have decisively shaped the history and culture of the American South from colonial times to the modern era. The essays in this interdisciplinary volume examine a wide range of topics, including race, migration, religion, law, slavery, emancipation, literature, memoir, popular culture, and ethnography. At a time when there is growing emphasis on globalizing southern studies the collection both demonstrates and critiques the value of Atlantic World perspectives on the region. Equally important, the mix of case studies and state-of-the field essays combines the latest historical thinking on the South\u27s myriad Atlantic World connections with the kinds of innovative cultural and literary scholarship associated with developments in the New Southern Studies. Ultimately, the volume reveals that there is still much to be learned about both the Atlantic World and the American South by considering them in tandem and from a variety of disciplinary perspectives. Moreover, by probing the Atlantic coordinates of the material, historical, emotional, intellectual, cultural, and symbolic South, these essays provide an important framework for better understanding the region and the succession of Atlantic Worlds to which it has long been intimately and distinctively connected. Brian Ward, professor in American studies at Northumbria University, is the author of Radio and the Struggle for Civil Rights in the South. Martyn Bone, associate professor of American literature at the University of Copenhagen, is the author of The Postsouthern Sense of Place in Contemporary Fiction. William A. Link, Richard J. Milbauer Professor of History at the University of Florida, is the author of Links: My Family in American History
Radical innovation for the wave energy sector: an investigation of the potential of direct conversion as an enabling technology
No full textWhile wave energy has been under development for over 40 years, as of 2023 it has not reached commercialisation. The wave energy sector has yet to develop a low-cost device that can demonstrate a level of reliable long-term electricity generation. At present, cost of energy estimates for early wave energy arrays are around an order of magnitude higher than mature renewables such as wind and solar PV. Improvements in the wave energy sector’s economic performance are therefore necessary for it to be competitive with other forms of low-carbon electricity supply. Performance improvements could come through incremental improvements which come alongside the scale-up and deployment of the technology. These incremental improvements are illustrated by the experience curve, where unit costs fall as a function of cumulative deployment. This experience curve relationship has been demonstrated in several mature, fully commercial, forms of renewable energy technology, such as solar PV and wind. Over time, the aggregation of these incremental improvements can make an initially expensive technology far more cost-competitive.
These incremental cost reductions are derived from several ‘learning effects’, including: learning by doing, economies of volume, economies of scale and incremental technology innovation. Alternatively, the performance improvements needed for the wave energy sector could come in part through radical technology innovation. This would entail a significant redesign of wave energy converters or their subsystems. In contrast to the incremental improvements alongside deployment, radical innovation could lead to a step-change in the performance of wave energy. Technologies such as direct conversion (which was studied in this thesis) could be enablers of radical innovation in the wave energy sector. This research investigates if radical innovation could enable low-cost wave energy, and if direct conversion technologies may have potential to deliver radical innovation in the wave energy sector. To carry out this investigation, the research was broken down into three main parts.
The first part of the research had the aim of evaluating the level of subsidy investment that may be required to enable cost-competitive wave energy. This would consider incremental, deployment-related cost reductions, or cost reductions through radical innovation. To do this, a learning investment model was developed for the wave energy sector. Learning investment was calculated as the additional investment to subsidise the deployment of wave energy in comparison to the cost of an incumbent form of generation. This is similar to the total subsidy through market-pull policy mechanisms. To develop a baseline cost reduction scenario for the wave energy sector, representing incremental cost reductions achieved alongside deployment, the experience curve approach was used. LCoE estimates for early commercial wave energy arrays, and estimated learning rates from the literature, were used to develop the baseline scenario. Following this, a set of alternative cost reduction pathways were developed that also included step-change cost reductions through radical innovation. These innovations were represented as discontinuities in the baseline wave energy experience curve. The level of innovation cost reduction, cost to develop and time to develop the radical innovations in these scenarios was based on data from wave energy innovation programmes and sector guidance documents. The learning investment model was then used to evaluate the investment associated with both the baseline incremental cost reduction scenario and the scenarios that included radical innovation.
The results from the first part of the research were that, for the wave energy sector to achieve a target LCoE of 100 EUR/MWh (representing the cost of an incumbent technology) through deployment-related cost reductions under the baseline assumptions, around 59 billion EUR is required in learning investment. However, this represents a lower limit to this investment, using baseline assumptions which are themselves relatively optimistic. If less optimistic assumptions are used, still within the range given in the literature, this total learning investment could be several hundreds of billions of EUR to achieve the LCoE target. When step-change cost reductions were introduced as a result of radical innovation, a large reduction in the total level of learning investment to achieve the LCoE target was observed in comparison with the base case deployment-only cost reduction scenario. These reductions in learning investment far outweighed the estimated cost of carrying out innovation programmes. This highlights that if the objective is to reach low-cost wave energy at the lowest possible public investment, supporting innovation programmes, even with low success rates, may offer the lowest cost pathway. A journal article was published based on the work that is presented in Part A of this thesis. This explored the learning investment associated with deployment and innovation related cost reduction scenarios for the wave energy sector.
Direct conversion technologies (DCTs) are a class of technology that directly convert mechanical energy to electrical energy. This class of technology has been identified as a potential enabler of radical innovation for the wave energy sector by several funding organisations. The second part of the research aimed to develop an assessment process to evaluate the potential of DCTs for wave energy applications, and then apply this process to a selection of DCTs. To do this, a set of measurable design agnostic parameters were identified which could indicate a DCT’s potential in several areas required for a high-performance wave energy converter. These assessment parameters were based on the conversion efficiency, energy density, material cost, lifetime energy output, durability and embodied carbon of the conversion technologies. A screening process was then developed where minimum performance levels were set for these parameters to indicate viability of a DCT in wave energy applications. Once the screening process was developed, six direct conversion technologies were assessed using the process: dielectric elastomer generators (DEG), dielectric fluid generators (DFG), piezoelectric polymer generators, piezoelectric ceramic generators, triboelectric generators and magnetostriction generators.
The results of part two of this research were that, of the six technologies that were assessed, four were rejected (piezoelectric polymer, piezoelectric ceramic, triboelectric and magnetostriction generators), as they demonstrated that they could not meet the required cut-off values in one or more of the assessment parameters. The other two technologies (dielectric elastomer and dielectric fluid generators) were allowed to pass the screening process as neither demonstrated that they could not meet the required cut-off values in any parameters. However, the process highlighted that there is limited publicly available data for some of the assessment parameters for both technologies — especially the parameters that required data on fatigue lifetime. This highlights that, of the technologies evaluated, only dielectric elastomer generators (DEGs) and dielectric fluid generators (DFGs) could be considered as viable options as an innovative technology for wave energy applications (using the cut-off values that were adopted in the screening process). Based on the parameters where comparable data existed, the most promising of these technologies was dielectric elastomer generators. Another significant benefit of having developed the process is its repeatability. The process was designed around parameters that should be measurable and relevant to a generic DCT that is considered for wave energy applications. Therefore, it can be used to assess other DCTs that are in future considered for wave energy applications, or to re-assess a technology if more data becomes available.
The third part of this research aimed to carry out a more in-depth evaluation of how the most promising DCT, identified in Part B of the research, could be developed for large-scale wave energy applications. As mentioned above, only dielectric elastomer generators and dielectric fluid generators were not rejected by the screening process. Of these two technologies DEGs were identified as the most promising DCT, based on the available comparable data. Part three of the research investigates the barriers to the development of dielectric elastomer generators for wave energy applications, along with actions that could be taken to address these barriers. To do this, the potential barriers to DEGs were identified though a literature review. As noted in Part B, in some areas there is limited data on DEGs for wave energy applications, given the sector’s maturity. Therefore, to build upon the literature review, expert opinion was solicited by carrying out a series of semi-structured interviews with experts in the field of dielectric elastomer generators and wave energy. These interviews were used to identify what the experts saw as key barriers to DEG WEC development, and add any barriers not captured by the literature review. The interviews were also used to gather expert opinion on what actions could be taken to address the barriers to DEG WECs, how difficult these actions may be to carry out, and if the experts believed there was a prioritisation in which the barriers should be addressed.
In the literature review, four high-level categories of barrier were established for DEG WECs. These were: Performance of the DEG, Manufacturing the DEG at scale, System integration for DEG WEC and Environmental effects of DEG. Within these categories, 13 subcategories were identified. During the semi-structured interviews, the experts were asked if these categories and subcategories covered the main barrier areas for DEG WECs. Eight of the nine experts agreed with the categories, with only one key barrier that did not fit in the original categories identified by the experts. During the course of the interviews, 33 key barriers were identified by the experts, with 35 actions identified that would address these barriers. Several common barriers and actions were identified by different experts, which highlighted areas of consensus. These also had large agreement with the literature review. This points towards clear barriers that need to be broken down for dielectric elastomer wave energy converter development, and actions that form the basis of future R&D activities that should be taken to address these. However, for some of the barriers and actions there was less consensus between the experts. For these barriers and actions, further work to help form consensus, such as workshops including a wider range of experts, may be beneficial in establishing appropriate R&D actions. Overall, the barriers and actions identified over the course of the literature review and semi-structured interviews highlighted the diverse range of barriers to DEG WEC development. The need for strong multidisciplinary collaboration, especially between industry and research organisations, was highlighted by several interviewees in order to address these barriers. This emphasised that ongoing communication, and a shared vision for the development of the technology between key stakeholders, would probably be beneficial in furthering dielectric elastomer-based wave energy conversion.
To summarise, the first part of this thesis establishes the potential benefits that radical innovation could bring to the wave energy sector, in terms of reducing the total investment in wave energy deployment required to achieve cost-competitive wave energy. The second part develops an evaluation process to identify direct conversion technologies that may be enablers of radical innovation in the wave energy sector and uses this process to assess six direct conversion technologies. The third part of the thesis carries out a more detailed evaluation of the most promising of these technologies, dielectric elastomer generators, with regard to the key barriers to the technology’s development and the actions that could be taken to overcome these barriers
Real-time correlators and hidden conformal symmetry in the Kerr/CFT correspondence
No full textIn this paper, we study the real-time correlators in Kerr/CFT, in the low frequency limit of generic non-extremal Kerr(-Newman) black holes. From the low frequency scattering off Kerr-Newman black holes, we show that for the uncharged scalar scattering, there exists hidden conformal symmetry on the solution space. Similar to Kerr case, this suggests that the Kerr-Newman black hole is dual to a two-dimensional CFT with central charges c(L) = c(R) = 12J and temperatures T-L = (r(+)+ r(-))-Q(2)/M/4 pi a, T-R = r(+)-r(-)/4 pi a. Using the Minkowski prescription, we compute the real-time correlators of a charged scalar and find perfect match with CFT prediction. We further discuss the low-frequency scattering of photons and gravitons by a Kerr black hole and find that their retarded Green's functions are in good agreement with CFT prediction. Our study shows that hidden conformal symmetry in the solution space is essential to set up and check the Kerr/CFT correspondence.Physics, Particles & FieldsSCI(E)28ARTICLE6nul
On holographic description of the Kerr-Newman-AdS-dS black holes
No full textIn this paper, we study the holographic description of the generic four-dimensional non-extremal Kerr-Newman-AdS-dS black holes. We find that if focusing on the near-horizon region, for the massless scalar scattering in the low-frequency limit, there exists hidden conformal symmetry on the solution space. Similar to the Kerr case, this suggests that the Kerr-Newman-AdS-dS black hole is dual to a two-dimensional CFT with central charges c(L) = c(R) = 6a(r+ +r*)/k and temperatures T-L = k(r(+)(2)+ r(*)(2) + 2a(2))/4 pi a Xi(r +1r(*)), T-R = k(r(+)- r(*))/4 pi Xi. The macroscopic Bekenstein-Hawking entropy could be recovered from the microscopic counting in dual CFT via the Cardy formula. Using the Minkowski prescription, we compute the real- time correlators of the scalar, photon and graviton in near horizon geometry of near extremal Kerr-AdS-dS black hole. In all these cases, the retarded Green's functions and the corresponding absorption cross sections are in perfect match with CFT prediction. We further discuss the low- frequency scattering of a charged scalar by a Kerr-Newman-AdS-dS black hole and find the dual CFT description.Physics, Particles & FieldsSCI(E)22ARTICLE8nul
Polynomial rings over Goldie-Kerr commutative rings
No full textAll rings in this paper are commutative, and
acc
⊥
\operatorname {acc} \bot
(resp.,
acc
⊕
\operatorname {acc} \, \oplus
) denotes the acc on annihilators (resp., on direct sums of ideals). Any subring of an
acc
⊥
\operatorname {acc} \bot
ring, e.g., of a Noetherian ring, is an
acc
⊥
\operatorname {acc} \bot
ring. Together,
acc
⊥
\operatorname {acc} \bot
and
acc
⊕
\operatorname {acc} \, \oplus
constitute the requirement for a ring to be a Goldie ring. Moreover, a ring
R
R
is Goldie iff its classical quotient ring
Q
Q
is Goldie. A ring
R
R
is a Kerr ring (the appellation is for J. Kerr, who in 1990 constructed the first Goldie rings not Kerr) iff the polynomial ring
R
[
x
]
R[x]
has
acc
⊥
\operatorname {acc} \bot
(in which case
R
R
must have
acc
⊥
\operatorname {acc} \bot
). By the Hilbert Basis theorem, if
S
S
is a Noetherian ring, then so is
S
[
x
]
S[x]
; hence, any subring
R
R
of a Noetherian ring is Kerr. In this note, using results of Levitzki, Herstein, Small, and the author, we show that any Goldie ring
R
R
such that
Q
=
Q
c
(
R
)
Q = {Q_c}(R)
has nil Jacobson radical (equivalently, the nil radical of
R
R
is an intersection of associated prime ideals) is Kerr in a very strong sense:
Q
Q
is Artinian and, hence, Noetherian (Theorems 1.1 and 2.2). As a corollary we prove that any Goldie ring
A
A
that is algebraic over a field
k
k
is Artinian, and, hence, any order
R
R
in
A
A
is a Kerr ring (Theorem 2.5 and Corollary 2.6). The same is true of any algebra
A
A
over a field
k
k
of cardinality exceeding the dimension of
A
A
(Corollary 2.7). Other Kerr rings are: reduced
acc
⊥
\operatorname {acc} \bot
rings and valuation rings with
acc
⊥
\operatorname {acc} \bot
(see 3.3 and 3.4).</p
Holographic description of Kerr-Bolt-AdS-dS spacetimes
No full textWe show that there exists a holographic 2D CFT description of a Kerr-Bolt-AdS-dS spacetime. We first consider the wave equation of a massless scalar field propagating in extremal Kerr-Bolt-AdS-dS spacetimes and find in the "near region", the wave equation in extremal limit could be written in terms of the SL(2, R) quadratic Casimir. This suggests that there exist dual CFT descriptions of these black holes. In the probe limit, we compute the scattering amplitudes of the scalar off the extremal black holes and find perfect agreement with the CFT prediction. Furthermore we study the holographic description of the generic four-dimensional non-extremal Kerr-Bolt-AdS-dS black holes. We find that if focusing on the near-horizon region, for the massless scalar scattering in the low-frequency limit, the radial equation could still be rewritten as the SL(2, R) quadratic Casimir, suggesting the existence of dual 2D description. We read the temperatures of the dual CFT from the conformal coordinates and obtain the central charges by studying the near-horizon geometry of near-extremal black holes. We recover the macroscopic entropy from the microscopic counting. We also show that for the super-radiant scattering, the retarded Green's functions and the corresponding absorption cross sections are in perfect match with CFT prediction. (C) 2011 Elsevier B.V. All rights reserved.Physics, Particles & FieldsSCI(E)11ARTICLE1108-12084
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