This paper theorizes Sankofa—the Akan principle of “return and retrieve”—as a decolonial praxis of ontological healing, memory, and African radical insurgence. Writing from a Ghanaian diasporic standpoint shaped by the crossings, frictions, and possibilities of U.S. academic life, I recount racial and ontological harms across my academic trajectory and examine how practices of Sankofa became literacies of healing. These literate acts include (a) traveling back to Ghana as a transnational re-education on Blackness, (b) witnessing African Americans’ somatic and sartorial rituals of healing at historic slave sites, (c) engaging Indigenous knowledge through encounters in a chief’s palace, and (d) enacting everyday literacies of cultural pride—such as wearing Ghanaian clothing—as somatic and symbolic resistance. Drawing on Critical Race Theory, Sankofa, and Global Black Rhetorics, I advance an interpretive heuristic in which Sankofa narrativization functions as a method, and the burdens of my racialized memories become the archive through which I theorize harm and healing. This work contributes to qualitative inquiry and Global Black Rhetorics by positioning African epistemologies not as mere cultural repositories but as methodological heuristics that expand how we understand healing, literacy, and decolonial research practice.

<p>Finding frequent itemsets is an essential researched technique and a challenging task of data mining. Traditional approaches for distributed frequent itemsets require massive communication overhead among different distributed datasets. In this paper, we adopt a new strategy for optimizing the time of communications/synchronizations from large datasets and, we present a novel algorithm for discovering frequent itemsets in different distributed datasets on the slave sites called finding efficient distributed frequent itemsets (FEDFI). The proposed algorithm is capable of generating the important frequent itemsets by applying an efficient technique for pruning the candidate itemsets. The experimental results confirm that our algorithm FEDFI performs better than Apriori and candidate distribution (CD) algorithms in terms of communication and computation costs.</p>

We have demonstrated a multiple-access transfer of time and frequency signal over a fiber and free-space link based on an optical frequency comb (OFC). With this transfer technique, two time–frequency signals were disseminated separately from a master site to two slave sites over a 3.9 km fiber and 100 m free-space link for 10,000 s. The timing fluctuations and instabilities of the time and frequency transfer were measured, estimated, and discussed. The experimental results show that the total root-mean-square (RMS) timing fluctuation of the transfer from site A to B is about 119 ps, with a fractional frequency instability on the order of 3.3 × 10−11 at 1 s and 2.8 × 10−14 at 2000 s. The RMS timing fluctuation of the transfer from site A to C is about 59.5 ps, with a fractional frequency instability on the order of 3.0 × 10−11 at 1 s and 2.6 × 10−14 at 2000 s. These results indicate that the multiple-access transfer technique proposed in this paper can provide important support for the application of a large-scale time–frequency synchronization network.

The increasing demand for a wheeled mobile robot (WMR) in many special fields (e.g., planetary exploration) has generated new difficulties, one of which is caused by the wheel longitudinal slippage on soft terrains. Compared with the general teleoperation under wheel pure rolling (no slippage), the introduction of wheel slippage creates new issues that potentially cause WMR instability. A new bilateral teleoperator for WMR coupling with dynamic longitudinal slippage is presented in this article. The traditional dynamic model is augmented in the presence of wheel slippage, whereas the slippage-induced unstable elements are determined through passivity analysis. To compensate for the active energy at the slave site, this article proposes a conservative slippage-dependent local controller without online estimation for wheel slippage. The teleoperator is then designed by guaranteeing the passivity of the entire teleoperation system. Experiments validate that the proposed methods can result in a stable system on soft terrains with good performance.

Teleoperation of wheeled mobile robots subject to longitudinal slipping and lateral sliding by time-domain passivity controller

Book Review| May 01 2021 Review: Slave Sites on Display: Reflecting Slavery’s Legacy through Contemporary Flash Moments, by Helena Woodard Slave Sites on Display: Reflecting Slavery’s Legacy through Contemporary Flash Moments by Helena Woodard. Jackson: University Press of Mississippi, 2019, 182 pp.; illustrations, notes, selected bibliography, index; clothbound, $99.00; paperback, $30.00; eBook, $28.50. Shawn Halifax Shawn Halifax Charleston County Park’s McLeod Plantation Historic Site Search for other works by this author on: This Site PubMed Google Scholar The Public Historian (2021) 43 (2): 150–152. https://doi.org/10.1525/tph.2021.43.2.150 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Shawn Halifax; Review: Slave Sites on Display: Reflecting Slavery’s Legacy through Contemporary Flash Moments, by Helena Woodard. The Public Historian 1 May 2021; 43 (2): 150–152. doi: https://doi.org/10.1525/tph.2021.43.2.150 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe Public Historian Search This content is only available via PDF. © 2021 by The Regents of the University of California and the National Council on Public History2021 Article PDF first page preview Close Modal You do not currently have access to this content.

Reviewed by: Slave Sites on Display: Reflecting Slavery’s Legacy through Contemporary “Flash” Moments by Helena Woodard Court Carney Slave Sites on Display: Reflecting Slavery’s Legacy through Contemporary “Flash” Moments. By Helena Woodard. African Diaspora Material Culture. (Jackson: University Press of Mississippi, 2019. Pp. vi, 182. Paper, $30.00, ISBN 978-1-4968-2417-2; cloth, $99.00, ISBN 978-1-4968-2416-5.) In 2019, set to coincide with the four-hundredth anniversary of the arrival of Africans to Virginia, the New York Times ran a series of essays (some written by academics, others by journalists) that contemplated in various ways the continued significance of that historic moment. The resultant controversy of the “1619 Project,” driven by a group of professional historians who disagreed in ways large and small with the scope and tenor of the essays, underscored the unfixed nature of the past and the persistent struggle to make cohesive sense out of a national history defined as much by its divisions and omissions as any unified vision of oneness. This media flashpoint served as a present-day reminder to the volatility of how the American past is continually framed and reframed (often hinged on conceptions of race and racism). These same issues of memory, memorialization, cultural forgetting, and the building of an incomplete history help frame Helena Woodard’s new book, Slave Sites on Display: Reflecting Slavery’s Legacy through Contemporary “Flash” Moments. Sitting at the center of this book is an important, if often undernuanced, set of questions: How do we balance understanding the past with presentism and the need for historical context? How has the past revealed itself through the prism of the present without being unwittingly corrupted by the present? How do museums and memorials allow for the past to be in the present without being of the present? But conversely: how do we capture the essence of the past at all without succumbing to the pressures of presentism? Woodard parses these complex issues through the examination of five memory sites: slave castles, the African Burial Ground in New York City, presidential estates, a reconstructed slave ship, and the slave memorial at Sullivan’s Island, South Carolina. These individual stories are connected rhetorically through Woodard’s use of the “flash” moment: “specific circumstances and/or seminal events within a geopolitical framework that binds the history of Atlantic slavery to its continued resonance or impact in the present” (p. 6). Thus, Woodard is set up to discuss the past and the present through the lens of race by way of this structure. The chapter on slave castles (with an important discussion of sankofa) is a good example of what this book does best: using a particular monument to get at the underlying complexity of how the past exists in the present. Other chapters, such as the one on the reimagining of a nineteenth-century slave ship and the importance of memorial discomfort, are also worth the read. The section on presidential estates (a study of the differing ways slavery is presented on George Washington’s, Thomas Jefferson’s, and Andrew Jackson’s plantations) could [End Page 161] use more historical buttressing to develop more thoroughly her larger argument. Still, at its best, Woodard’s book offers a multifaceted examination of the power the past has on the present and the present has on the past. What makes the 1619 story, or the Olaudah Equiano story, or the story of slave castles so powerful is that they contain immediate truths, confirmed falsehoods, and enough uncertainty to bend and warp within any chosen narrative. This knot of ambiguity might play out well in the classroom, where discussion and critical thinking are key, but once these stories become embedded in public monuments or memorials, they become fixed; the vibrations of knowing and unknowing turn static as they emerge as fact. Does a quasi-historical (even antihistorical) monument provide enough meaning—however wrongheaded—to justify its place in the present moment? Can Equiano or the Door of No Return, in other words, have a rhetorical power beyond the limits of their current formulation? Are monuments real enough or teachable enough on their own terms—however flawed—or are...

Reviewed by: Slave Sites on Display: Reflecting Slavery's Legacy through Contemporary "Flash" Moments by Helena Woodard William R. Nash Helena Woodard. Slave Sites on Display: Reflecting Slavery's Legacy through Contemporary "Flash" Moments. Jackson: UP of Mississippi, 2019. 190 pp. $30.00. In the mid-1990s, as a freshly minted PhD with a specialization in Black literature, I visited Monticello with my partner, a specialist in nineteenth-century American literature, as part of a literary tour of Virginia. Having heard a "shiny" version of Poe's history in Richmond the day before, where a docent insisted to us that the author did not have a substance problem, I was more than a little curious about what we would hear on Jefferson's mountaintop about enslavement. Standing near the spot where preservationists were excavating a slave dwelling, our tour guide spoke at length about how the "servants" at Monticello ate the same food and got the same medical care as "Mr. Jefferson himself." To be fair, Monticello cannot stand for all historical sites treating the history of enslavement; furthermore, much has changed there since the 1990s. Still, in the course of my career teaching about [End Page 269] enslavement, I have told that story many times, trying to help students grasp how history is perpetually made and remade. With Helena Woodard's excellent new book in hand, I now can bring that experience into the classroom with more nuance, depth, and clarity than I have heretofore been able to achieve. In Slave Sites on Display, Woodard taps into the contemporary racial zeitgeist and provides scholars and teachers with the necessary tools for navigating some of the most pressing issues we and our students must currently face. Living as we do in a moment when attention to sites associated with enslavement is on the rise, as more and more Americans wake up to the absolute necessity of engaging with our national past, as the ripple effects from the influential 1619 Project continue to spread, we need not only to acknowledge the past but also connect it to events unfolding in our increasingly fraught society. Woodard is spot-on in this regard, as she notes in her Introduction: "in this study I ponder how a slave site that symbolizes the past can also express itself opportunistically as [an] unforgiving mirror … of ongoing, present-day racial dilemmas" (6). Simultaneously theoretically sophisticated and accessible in her prose, Woodard joins scholars like Steven Katz by grounding her assessment of modern slave sites in concepts from Holocaust studies. While this comparison is not uncontroversial, it works well for Woodard. Referring to Walter Benjamin's "recalibrations of a past/present dialectical constellation through 'flash' moments," Woodard argues that these tensions, when mapped onto the experience of visiting sites memorializing enslavement in the context of "seminal events or specific circumstances … have the potential to redefine the slave past, which still infringes upon the lives of diaspora slave descendants" (7). Put another way, Woodard enables readers to think about how their ways of seeing enslavement memorials are shaped by the moments in which people visit them. This functions both on the level of an individual's experience and as a shaper of broader cultural understandings of enslavement. By way of illustration, she contrasts President Obama's visits to slave forts in Senegal and Ghana with visits to Gorée Island's House of Slaves by former presidents Clinton and George W. Bush, arguing that for some the picture of a Black American leader standing at a site where the middle passage originated suggests a different view of how enslavement has circumscribed the possibilities of Black lives. In addition to treating slave fort sites on the African continent, Woodard also explores a range of sites in the United States, which gives her argument both transnational breadth and an American depth that heightens its effectiveness. The book contains chapters on the African Burial Ground in New York City; the treatment of enslavement at presidential estates like Monticello, Washington's Mount Vernon, and Jackson's Hermitage; traveling slave ship exhibitions at anchor in London, Charleston, South Carolina, and Jacksonville, Florida; and the first Bench by the Road memorial in Sullivan's Island...

This paper presents a new master manipulator applied to robotic systems for arrhythmia ablation. The manipulator is designed to implement the concept of two different master-slave teleoperation controls in the clinical application. One is the conventional control between the master and catheter-handle in the slave site and the other is catheter tip manipulation corresponding the master motion. For the purpose, the master has six degrees of freedom (DOF) and consists of three main components: a spherical mechanism for rotational motion of 2-DOF, 3-RRR planar parallel mechanism with 3-DOF, and counter-weight lifting mechanism for the vertical movement. Two mechanisms except the lifting mechanism are parallel chains and structurally more complicated. Therefore, their forward kinematics are analyzed, and workspaces are simulated. To evaluate the applicability for robotic catheter systems, the manipulator prototype was tested for its smoothness, workspace, and teleoperation performance. The subjects in the smoothness test reported no considerable friction and jerk in free movement in the three-dimensional space as shown in the recorded curves. The workspace test shows the actual workspace is similar to the simulated one except some structural constraints in the 3-RRR mechanism. For the last test, a robotic catheter teleoperation system with a slave robot and the software structure for the robotic catheter control system with electrical connection of each component were built. The result performed by five different users shows the motion of the slave robot well tracks that of the master device with small average errors and time delay that are acceptable in robotic catheter teleoperation systems.

ABSTRACTThis paper examines the relationship between motivation, experience, and post-purchase intentions of five ethnic tourist segments at Trans-Atlantic Slave Trade attractions. Multi-group invariance test on 783 tourists revealed that relaxation motivation influenced the emotional experience of all ethnicities except Blacks in the diaspora whose emotional experience was influenced by social motives. Educational motivation influenced the educational experience of all segments except Black Africans though it impacted their aesthetic experience. Emotional experience influenced the behavioural intention of Blacks in the diaspora, Caucasian Americans, and Europeans while educational experience influenced that of Black Europeans and Africans. Implications of the findings are discussed.

This paper aims to develop an innovative approach named sensorless force feedback joystick control for teleoperation of construction equipment. First, a force sensorless supervisory controller is designed with two advanced modules: a neural network-based environment classifier to estimate environment characteristics without requiring a force sensor and, a fuzzy-based force feedback tuner to generate properly a force reflection to the joystick. Second, two local robust adaptive controllers are simply built using neural network and Lyapunov stability condition to ensure desired task performances at both master and slave sites. A teleoperation system is setup to demonstrate the applicability of the proposed approach.

Abstract This paper explores the social distance between local residents and African–Americans who have settled in Ghana since the 1960s. Data generated from in‐depth interviews suggest the African–American expatriates felt their proximity to collective slave memory or particularly slavery heritage conferred on them certain rights to exclude local residents who are more susceptible to forgetting the past. By appropriating traces of the past, the African–American expatriates provide a range of tourism services, albeit to visitors they believed subscribed to socially constructed meanings elicited at slave sites. The study suggests explicit recognition of African–American expatriates in the levels of contestations that result from slavery‐based heritage tourism.

This paper reports technical design of a novel experimental test facility, using haptic-enabled teleoperation of robotic manipulators, for live transmission line maintenance. The goal is to study and develop appropriate techniques in repair overhead power transmission lines by allowing linemen to wirelessly guide a remote manipulator, installed on a crane bucket, to execute dexterous maintenance tasks, such as twisting a tie wire around a cable. Challenges and solutions for developing such a system are outlined. The test facility consists of a PHANToM Desktop haptic device (master site), an industrial hydraulic manipulator (slave site) mounted atop a Stewart platform, and a wireless communication channel connecting the master and slave sites. The teleoperated system is tested under different force feedback schemes, while the base is excited and the communication channel is delayed and/or lossy to emulate realistic network behaviors. The force feedback schemes are: virtual fixture, augmentation force and augmented virtual fixture. Performance of each scheme is evaluated under three measures: task completion time, number of failed trials and displacement of the slave manipulator end-effector. The developed test rig has been shown to be successful in performing haptic-enabled teleoperation for live-line maintenance in a laboratory setting. The authors aim at establishing a benchmark test facility for objective evaluation of ideas and concepts in the teleoperation of live-line maintenance tasks.

Teleoperating cyber-physical system (TCPS) has been considered as a promising technology to stretch artificial intelligences to remote locations. Many applications of TCPS demand operator and slaves to keep state consensus on the shared information. However, the cyber- and physical- constrained characteristics on TCPS make it difficult to realize such a consensus. This paper investigates the consensus problem for single-master-multi-slave TCPS with time-varying delay and actuator saturation. According to the communication structures of slaves, centralized and decentralized controllers are, respectively, designed to drive the consensus of master and slave robots. To simplify the information fusion in decentralized controller design, we use min-weighted rigid graph-based topology optimization algorithm to reduce the communication redundancy in slave site. Under time-varying delay and actuator saturation constraints, the sufficient stability conditions are presented to show that the centralized and decentralized controllers can stabilize the single-master-multi-slave TCPS. Moreover, the stability conditions are rearranged into a form of linear matrix inequalities, and then, the required initial stability conditions for master and slaves are developed. Finally, simulations and experiments are demonstrated to show the validity of the method. It is shown that the consensus controllers can guarantee the asymptotic stability of single-master-multi-slave TCPS, while the topology optimization can reduce the redundancy of communication links.

This paper presents a geometrically and dynamically transparent projected predictive Energy-Bounding Approach (EBA) for multiple degree-of-freedom (m-DOF) haptic teleoperation with time delays. The straightforward extension of a single-DOF teleoperation to m-DOF teleoperation suffers from a bad force distortion problem that becomes worse with the increase in communication time delays between master and slave sites. Due to this, geometry perception of remote m-DOF objects at master site is severely deteriorated. To solve this problem, a projected predictive m-DOF EBA is proposed by combining the m-DOF Predictive EBA and the projection method that can compensate the force distortion problem. The proposed approach also includes steps to get stably the information about the contact locations (geometry) of m-DOF remote objects without geometry detection sensors. In order to validate the proposed approach, some experiments performing surface contour-following are conducted using two Phantoms: (i) 2-DOF object (bobbin), and (ii) 3-DOF semi-spherical object in the presence of large time delays.

Position referenced force augmentation in teleoperated hydraulic manipulators operating under delayed and lossy networks: A pilot study

A predictive energy-bounding approach for Haptic teleoperation

Distributed formation control for teleoperating cyber-physical system under time delay and actuator saturation constrains

This paper introduces a novel haptic-enabled magnetic micromanipulation platform with promising potential for extensive biological and biomedical applications. This platform consists of two separated basic sites: 1) the slave site that uses a controlled magnetic field for manipulating a ferromagnetic microdevice and 2) the master site that uses a haptic-enabled device for the position and the force communication between the human operator and the microdevice. Due to the size restriction of the microdevice, attaching force sensors to the microdevice is impractical. Thus, to preserve a high feeling of a microdomain environment for the human operator, the applied force/torque from the environment to the microdevice is estimated with a novel off-board force sensing mechanism. This force sensing mechanism uses the produced magnetic flux information and the real position of the microdevice to estimate the environmental force applied to the microdevice. A scaled force-position teleoperation scheme is employed for this haptic application to scale down the macrodomain position for microdomain application and scale up the microdomain force for macrodomain sensing of the human operator. Conducting several experiments in different conditions, precise motion tracking with high accurate force transfer to human operator has been reported, RMS of position tracking errors of 0.2 mm with 1.27- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math>$\mu$</tex-math></inline-formula> N accuracy force sensing for single-axis motion.

This paper studies the consensus problem for teleoperation system over communication networks. Compared with previous work, both multi-slave configuration and time variable delays are considered. According to the topology structure of slave robots, centralized and distributed consensus controllers are respectively designed, where a leader-following strategy is adopted. During the design process of distributed controllers, min-weighted rigid graph is used to optimize the topology structure of slave robots. With the optimized topology, the amount of communication links and energy dissipations in slave site can be reduced. Moreover, the sufficient stability conditions are presented to show the consensus controllers can stabilize the master-slave system under variable time delay. Finally, simulation results are performed to show the effectiveness of the main results.