Single Slave Research Articles

SPI Master Slave Communication

The serial-peripheral interface (SPI) protocol also called asynchronous serial interface specification is used for communication between single master and single/multiple slaves. With the increase in number of slaves causing high complexity of circuit creates a demand in self-test ability feature for SPI module in order to test for fault free circuits. Built-In-Self-Test (BIST) in the answer for self-test in circuits as well as it helps in reduction of maintenance and testing cost. Design of BIST embedded SPI module with single master and single slave configuration has been introduced in these paper, Here 8-bit is transferred across the module, Where the Circuit under Test (CUT) is being Self-Tested with BIST feature for its correctness. This SPI module is designed using Verilog hardware description language(HDL) using EDA playground platform for application like applications specific integrated circuit (ASIC) or system on chip (SOC). SPI stands for the Serial Peripheral Interface. It is a serial communication protocol that is used to connect low-speed devices. It was developed by Motorola in the mid-1980 for inter-chip communication. It is commonly used for communication with flash memory, sensors, real-time clock (RTC), analog-to-digital converters, and more. It is a full-duplex synchronous serial communication, which means that data can be simultaneously transmitted from both directions. The main advantage of the SPI is to transfer the data without any interruption. Many bits can be sent or received at a time in this protocol. In this protocol, devices are communicated in the master-slave relationship. The master device controls the slave device, and the slave device takes the instruction from the master device. The simplest configuration of the Serial Peripheral Interface (SPI) is a combination of a single slave and a single master. But, one master device can control multiple slave devices

Sliding Mode Impedance Control for Dual Hand Master Single Slave Teleoperation Systems

For the purpose of avoiding injury and realizing precise operations, the multilateral teleoperation system is the most efficient way to transport trace toxic or radioactive substances, to perform minimally invasive surgery, etc. It is essential to enhance the transparency of a multilateral teleoperation system including multiple masters and the single slave manipulator. However, there are few researchers focus on the allocation of the contact force of the single slave manipulator to different master manipulators. In this paper, we firstly introduce the concept of force translation for teleoperation systems consisting of dual hand master (left and right hands) manipulators and a single slave manipulator. Force translation reflects how the impedance on the single slave side is translated or allocated to contact forces on different master sides. To maintain the stability of the system and to improve transparency, we elucidate the mechanism of the force translation and analyze the relation among masters and the slave. Furthermore, the force translation mechanism is analyzed through numerical simulations and CHAI 3D virtual physical simulations. It is used to propose a multilateral impedance control, and the Lyapunov function is used to analyze the system stability. The results of numerical simulations and real robot experiments verify the effectiveness of the proposed control methods based on the proposed force translation mechanism.

Letter to the Editor

Letter to the Editor John Adam To the editors and readers of The Michigan Historical Review: Governor Gretchen Whitmer issued 193 executive orders in 2020. Most addressed COVID-19 pandemic issues; however, Executive Order 2020-139 (issued in June) renamed Lansing's Lewis Cass Building as the Elliott-Larsen Building. Governor Whitmer renamed the building without consulting any Michigan historical organization and without approval of the legislature, even though it was named the Lewis Cass Building by a 1952 Michigan House of Representatives concurrent resolution. The governor says that no one can deny the important role Cass played in Michigan and the nation's early history. But the governor did not say what Cass did, did not consider the historical context in which he lived, and did not explain that his position on these issues were the positions of the Democratic Party and its leaders. Instead, the governor justified the renaming by claiming that "Cass owned a slave; defended a system to permit the expansion of slavery; and implemented a policy that forcibly removed Native Americans from their tribal lands." The governor should be careful in cherry-picking the record of Cass and in making retroactive assessments of this nineteenth-century politician. Cass, a Democratic Party politician for five decades, should be judged in full historical context. Trained as a lawyer, he had an impressive resume. He was a member of the Ohio legislature (1806), US marshal of Ohio (1807-1812), colonel during the War of 1812, governor of the Michigan Territory (1813-1818, 1820, 1822-1823, 1825-1826, 1828-1829), and served concurrently as superintendent of Indian Affairs (1813-1831), secretary of war (1831-1836) under President Andrew Jackson, minister to France under Jackson and President Martin Van Buren (1836-1842), Michigan senator (1845-1847), 1848 Democratic presidential candidate (losing to Zachary Taylor), again Michigan senator (1849-1857), and secretary of state (1858-1860) under President James Buchanan. Governor Whitmer's criticisms would apply to almost every Democratic officeholder during Cass's lifetime and later. The governor's statement that Cass owned a single slave was odd, so I tried to find the basis for this [End Page 171] claim. I believe the source is William Klunder's 1996 book Lewis Cass and the Politics of Moderation (Kent State University Press). Klunder wrote that, while Cass said he never owned a slave, a "note written to Cass by General Alexander Macomb reveals that the governor was negotiating with the general's cousin, David Betton Macomb, to sell a slave." (47) Klunder believes Cass owned a slave used for domestic work. If it is true that Cass owned a slave, and the evidence is weak on this, we know that many of our greatest leaders owned slaves. Indeed, consider US Supreme Court Justice John Marshall Harlan (1833-1911), who dissented in the landmark case of Plessy v. Ferguson (1896). Justice Harlan wrote that "our constitution is color-blind." But, as Peter Canellos notes in his book The Great Dissenter (Simon and Schuster, 2021), before that Harlan "owned slaves and supported slavery right up through the Civil War," and was on the "record as having initially opposed the postwar amendments to the Constitution, maintaining that his state of Kentucky—which had painfully resisted the Confederacy—should be rewarded by getting to make its own decision on whether to free its slaves based on a popular vote." (19) Cass was not an abolitionist (nor was Abraham Lincoln), but he was anti-slavery. Like Illinois Senator Stephen A. Douglas and other northern Democrats, Cass was a proponent of "popular sovereignty" as a route to avoid civil war. Cass advocated sectional compromise with the slave states to keep the nation from violent conflict. The Democratic Party in 1856 ran on a platform that embraced the popular sovereignty argument. This allowed people residing in new territories to decide if new states would permit slavery or not. Moreover, Cass resigned as secretary of state in 1860 in protest over President Buchanan's refusal to reinforce Fort Sumter and the defenses surrounding Charleston, South Carolina. Cass fully supported the Union during the subsequent war, as articulated by historical works such as Frank B. Woodford's Lewis Cass...

Underwater multilateral tele-operation control with constant time delays

In the complex underwater environment, it is difficult to complete teleoperation tasks due to dynamic environments. Through cooperation among manipulators, a multilateral teleoperation system has the potential to achieve better performance than conventional bilateral teleoperation systems. In this paper, we propose a multilateral teleoperation control method that can be easily applied for underwater grasping tasks. Specifically, a new structure involving two (or multiple) masters and a single slave is investigated, which is treated as a linear combination of multiple subsystems under time delays. A control method based on linear matrix inequality exponential convergence and nonlinear disturbance is presented to estimate the model uncertainties of the system and unknown external disturbances during grasping process. The asymptotic stability is analyzed using the established Lyapunov–Krasovskii functional. Numerical simulations and real experiments performed for the task of grasping a plastic foam block are reported to verify the proposed control method in real applications.

Verification of Wishbone Bus Interface for SoC using System Verilog and UVM

The Verification phase carries important role in design cycle of a system on chip. Verification gives with the actual enactment and functionality of a DUT and to verify the design meets the system requirements. This paper present wishbone bus interface for soc integration to interconnect architecture for portable IP cores and test bench is developed in system Verilog and verification is done by both system Verilog verification methodology and universal verification methodology which includes scoreboard, functional coverage and assertion. This paper based on two application to integrate IP cores that is single master with single slave interconnection and single master with multiple slave interconnections where master is test bench and slave will be a core.

Design & Verification of Serial Peripheral Interface (SPI) Protocol

SPI (Serial Peripheral Interface), which was introduced by the company Motorola, and it is a protocol for communication of serial synchronous about the communication among the master and slave device, which is also used to provide communiqué between microcontroller and many devices which are additional and similar to external Analog to the Digital Converters, Digital to Analog Converters, and EEPROMs. Now a days, communication protocols are at low end. There are two different Protocols: 1) Inter-I2C and 2) SPI. Both of these protocols are well designed for the communications between the Integrated Circuits for communication with On-Board Peripherals. SPI is most commonly used protocol for both intra-chip and inter-chip, and is used at low or medium speed of data-stream transfer. This paper introduces about the quality of SPI Interface Protocol with Single Master and Single Slave configuration, which involves 8-bit of the data transfer and all necessary incorporates features that required for modern applications such as ASIC or SOC (System on Chip). The SPI design is verified and implemented by using System Verilog to show their coverage code and their functional correctness, the entire RTL was written using Verilog for Synthesis and then the Verification architecture is written using System Verilog. The implementation is done using Spartan 3E.

Free and Brave

Free and Brave Caroline Knight (bio) For the land of the free, and the home of the brave.where brave means taking a step outside of my parents' homeand recognizing i'm in a target zone.my leg, 2 cops go free unknown.my stomach, 4 cops.my neck, 6 stomps crushing my bones.my head? no need. i'm already dead.it shouldn't make sense that i'm so tense,that i literally shake in the presence of civil defense,that my life is a story and it's always full of suspense,because tomorrow is not a promise to me and the black community.i have a degree in police brutality,taken 16 years of this native language, spoken internationallyyet i don't enunciate fluently because je ne comprends pas pourquoi le racisme est ici. brave means attending an institutionthat uses the mathematical art of substitutionto replace black excellence with the laws of isaac newton.i speak in proper english for i only wishpeople could see me as perfect.it's a different tongue i use around the school,not to look cool, but so i look more pronounced and stand out in the college application pool.i utilize every opportunity propelled, kicked, shot at meand collect the information in its entirety.do you see my broad vocabulary?secondary resources is what i rely on to succeedbecause i can't change the fact that my education cost whiteTEEN.99this system's education was not built for a black girl named caroline; a girl who believesin the idea of diversity, but has yet to see her wish of appreciation for her melanin skin come true. [End Page 557] 5 plus 6 equals 11, the year that SATs are in session,meaning college board is getting their wealthbut somehow forgotten that this amountwas the number of times eric garner screamed for help.i can't breathe, i can't breathe, i can't breathe, i can't breathe,i can't breathe, i can't breathe, i can't breathe, i can't breathe,i can't breathe, i can't breathe, i can't breathe.he can no longer speak for the man is deceased.may his soul rest in peace. sometimes, i just have to wonder,what would francis scott key thinkif he were to witness what happened in our world today:"the land of the free and the home of the brave"?when writing those words, did he imaginethat those phrases were a lie?that they defy the foundation this country was built on?he should've written"for your white supremacy and the home of the slave." free means i proudly speak of black historywith no restraints. this is not the first time the truthhas disappeared because of this system's fear that we are here, together,white and minority ears hear the same message, "change is near."it is everywhere we acknowledge that posting isn't enough andmurdering is beyond too much.it is white people memorizing dr. king's words:"injustice anywhere is a threat to justice everywhere."it is understanding that protests are peaceful until the police become lethal.it is knowing the names of every single slave that survived the plague known as today. we don't demand justice, we deserve it.it shouldn't be some prize we have to idolize, rather a goal we can control.much like how the national guard proposes the use of guns and horsesto trample our justified ideals and hopes, to reveal that black lives matter should be real. [End Page 558] george floyd gasped for air, not only because he couldn't breathe, but because he couldn't seea future where his family was not screaming due to the knee of a white man serving the system's police.regis korchinski-paquet was falling for a few seconds, but some see that time as worthless because it's all the life she had left.our skin is confident, our being is prominent,and i will not stop writing until we are not seenas approximates...

Message delay time distribution analysis for controller area network under errors

Controller area network (CAN) is a widely used fieldbus protocol in various industrial applications. To understand the network behavior under errors for the optimal design of networked control systems, the message response time of the CAN network needs to be analyzed. In this study, a novel delay time distribution analysis method for the response messages is proposed when considering errors. In this method the complex message queues are decomposed into typical message patterns and cases. First, a stochastic fault model is developed, and the probability factor is defined to calculate the error distribution. Then the message delay time distribution for the single slave node configuration is analyzed based on the error distribution. Next, based on the delay time distribution analysis of typical patterns and cases, an analysis framework of message delay time distribution for the master/slave configuration is developed. The testbed is constructed and case studies are conducted to demonstrate the proposed methodology under different network configurations. Experimental results show that the delay time distributions calculated by the proposed method agree well with the actual observations

Verification of Driver Logic Using AMBA-AXI UVM

Advanced Extensible Interface (AXI) is the most commonly used bus protocols in the day-to-day because of its high performance and high-frequency operation without using complex bridges. AXI is also backwardcompatible with existing AHB and APB interfaces. So verification of driver logic using AMBA-AXI UVM is presented in this paper. The AXI is used for multiple outstanding operations which is only possible in the other protocol but it is possible in AXI because it contains different write address and data channels and AXI also supports out of order transfer based on the transaction ID which is generated at the start of the transfer. The driver logic for the AXI has been designed and implemented using the Universal Verification Methodology (UVM). The signaling of the five channels such as write address, write data, write response, read address, read data channel of AXI protocol are considered for verification. According to the AXI protocol,the signals of these channels are driven to the interconnect and results are observed for single master and single slave. The driver logic has been implemented and verified successfully according to AXI protocol using the Rivera Pro. The results observed for single master and single slave have shown the correctness of AMBA-AXI design in Verilog.

Difference Synchronization of Identical and Nonidentical Chaotic and Hyperchaotic Systems of Different Orders Using Active Backstepping Design

This paper introduces a new type of synchronization scheme, referred to as difference synchronization scheme, wherein the difference between the state variables of two master [slave] systems synchronizes with the state variable of a single slave [master] system. Using the Lyapunov stability theory and the active backstepping technique, controllers are derived to achieve the difference synchronization of three identical hyperchaotic Liu systems evolving from different initial conditions, as well as the difference synchronization of three nonidentical systems of different orders, comprising the 3D Lorenz chaotic system, 3D Chen chaotic system, and the 4D hyperchaotic Liu system. Numerical simulations are presented to demonstrate the validity and feasibility of the theoretical analysis. The development of difference synchronization scheme has increases the number of existing chaos synchronization scheme.

Verification of Driver Logic Using AMBA-AXI UVM

Advanced Extensible Interface (AXI) is the most commonly used bus protocols in the day-to-day because of its high performance and high-frequency operation without using complex bridges. AXI is also backwardcompatible with existing AHB and APB interfaces. So verification of driver logic using AMBA-AXI UVM is presented in this paper. The AXI is used for multiple outstanding operations which is only possible in the other protocol but it is possible in AXI because it contains different write address and data channels and AXI also supports out of order transfer based on the transaction ID which is generated at the start of the transfer. The driver logic for the AXI has been designed and implemented using the Universal Verification Methodology (UVM). The signaling of the five channels such as write address, write data, write response, read address, read data channel of AXI protocol are considered for verification. According to the AXI protocol,the signals of these channels are driven to the interconnect and results are observed for single master and single slave. The driver logic has been implemented and verified successfully according to AXI protocol using the Rivera Pro. The results observed for single master and single slave have shown the correctness of AMBA-AXI design in Verilog.

A Time-Delayed Multi-Master-Single-Slave Non-Linear Tele-Robotic System Through State Convergence

This paper presents the design of a multi-master–single-slave nonlinear tele-robotic system working in the presence of time varying delays. The structure of the proposed tele-robotic system is derived from the extended state convergence architecture and the control objective is defined as the position regulation of the slave manipulator. The desired reference value for the slave manipulator is set by the master systems according to their authority levels. To ensure that the tele-robotic system remains stable in the presence of time varying delays and the control objective is also achieved, Lyapunov-based stability analysis is carried out which results in certain guidelines to be followed for the selection of the control gains. In order to check the validity of the proposed scheme, MATLAB simulations are performed on a two degrees-of-freedom nonlinear tele-robotic system containing three master and single slave manipulators. Simulation results suggest that the proposed scheme is viable and can be deployed to control a class of multilateral nonlinear tele-robotic systems.

Performance Evaluation of Bluetooth Low Energy for High Data Rate Body Area Networks

Bluetooth Low Energy (BLE) is a promising wireless network technology, in the context of body area network (BAN) applications, to provide the required quality of service support concerning the communication between sensor nodes placed on a user's body and a personal device, such as a smartphone. Most previous BLE performance studies in the literature have focused primarily in networks with a single slave (point-to-point link) or traffic scenarios with relatively low data rate. However, many BAN sensors generate high data rate traffic, and several sensor nodes (slaves) may be actively sending data in the same BAN. Therefore, this work focuses on the evaluation of the suitability of BLE mainly under these conditions. Results show that, for the same traffic, the BLE protocol presents lower energy consumption and supports more sensor nodes than an alternative IEEE 802.15.4-based protocol. This study also identifies and characterizes some implementation constraints on the tested platforms that impose limits on the achievable performance.

2C31 BILATERAL TELEOPERATION CONTROL BASED ON SCATTERING AND VIRTUAL DAMPING(The 12th International Conference on Motion and Vibration Control)

This paper proposes a new bilateral control method of Single Master and Single Slave (SMSS) Tele-robot system. In this strategy, we propose a combination control method between PD and Scattering and Virtual Damping parameters to improve the tracking performance and transparency of Tele-robot, the reflecting force from slave side will be stable. Using Lyapunov technique, we can achieve the global stability of the control law. The achievement results of the proposed method are shown with the transparency improvement such as position and force between both sides of the Tele-robot system in two cases: the slave moves without any contact and the slave moves in contact with the environment. The simulation results showed the effectiveness of our proposed control method.

The Remote Control a Tele-Robot 5R by Using Dual-Tone Modulation

This paper proposes replacement of a tele-controller system to base on DTMF in spite of tele-system web. It is found that telesystem with Dual Tone Multiple Frequency has a large capability in send-receiving of data in hardware and software. It dos not need to install of a PC for receiving and processing of data as tone modulated form from slave side. In other hand, its adaptive ability with different phone lines and no any need to spare devices of network such as net card or modem and no contribution from local networks of internet and finally different master interfacing capabilities with a single slave are examples of the advantages of the system. Also, synchronous using of internet lines like ADSL in other applications such as video image sending (due to system development) is one of the other advantages of it. This paper describes several interface system and control system with experimentally tests according to the ISO9283 standard and Delay-Time in this the Tele-Robot.

Evaluation of a 433 MHz band body sensor network for biomedical applications.

Body sensor networks (BSN) are an important research topic due to various advantages over conventional measurement equipment. One main advantage is the feasibility to deploy a BSN system for 24/7 health monitoring applications. The requirements for such an application are miniaturization of the network nodes and the use of wireless data transmission technologies to ensure wearability and ease of use. Therefore, the reliability of such a system depends on the quality of the wireless data transmission. At present, most BSNs use ZigBee or other IEEE 802.15.4 based transmission technologies. Here, we evaluated the performance of a wireless transmission system of a novel BSN for biomedical applications in the 433 MHz ISM band, called Integrated Posture and Activity NEtwork by Medit Aachen (IPANEMA) BSN. The 433 MHz ISM band is used mostly by implanted sensors and thus allows easy integration of such into the BSN. Multiple measurement scenarios have been assessed, including varying antenna orientations, transmission distances and the number of network participants. The mean packet loss rate (PLR) was 0.63% for a single slave, which is comparable to IEEE 802.15.4 BSNs in the proximity of Bluetooth or WiFi networks. Secondly, an enhanced version is evaluated during on-body measurements with five slaves. The mean PLR results show a comparable good performance for measurements on a treadmill (2.5%), an outdoor track (3.4%) and in a climate chamber (1.5%).

Information flow during gene activation by signaling molecules: ethylene transduction in Arabidopsis cells as a study system.

BackgroundWe study root cells from the model plant Arabidopsis thaliana and the communication channel conformed by the ethylene signal transduction pathway. A basic equation taken from our previous work relates the probability of expression of the gene ERF1 to the concentration of ethylene.ResultsThe above equation is used to compute the Shannon entropy (H) or degree of uncertainty that the genetic machinery has during the decoding of the message encoded by the ethylene specific receptors embedded in the endoplasmic reticulum membrane and transmitted into the nucleus by the ethylene signaling pathway. We show that the amount of information associated with the expression of the master gene ERF1 (Ethylene Response Factor 1) can be computed. Then we examine the system response to sinusoidal input signals with varying frequencies to determine if the cell can distinguish between different regimes of information flow from the environment. Our results demonstrate that the amount of information managed by the root cell can be correlated with the frequency of the input signal.ConclusionThe ethylene signaling pathway cuts off very low and very high frequencies, allowing a window of frequency response in which the nucleus reads the incoming message as a sinusoidal input. Out of this window the nucleus reads the input message as an approximately non-varying one. From this frequency response analysis we estimate: a) the gain of the system during the synthesis of the protein ERF1 (~-5.6 dB); b) the rate of information transfer (0.003 bits) during the transport of each new ERF1 molecule into the nucleus and c) the time of synthesis of each new ERF1 molecule (~21.3 s). Finally, we demonstrate that in the case of the system of a single master gene (ERF1) and a single slave gene (HLS1), the total Shannon entropy is completely determined by the uncertainty associated with the expression of the master gene. A second proposition shows that the Shannon entropy associated with the expression of the HLS1 gene determines the information content of the system that is related to the interaction of the antagonistic genes ARF1, 2 and HLS1.

Afterword: Rough crossings to new beginnings

Afterword: Rough crossings to new beginnings Deirdre Coleman The proposed ‘Freedom Tower’, the centrepiece of the rebuilding plan for New York’s World Trade Centre site, is to rise from the ashes of Ground Zero to a height of 1776 feet, an architectural tribute to the year the United States declared its independence as a nation. In Rough Crossings, a dramatic history of the American War of Independence, Simon Schama shows how the meaning of this war gets turned upside down if viewed through the eyes of black slaves.1 These slaves, lured by the promises of freedom made by the British, fled their American rebel masters in order to rally under the flag of King George. From their perspective, a much-vaunted war for liberty on behalf of whites was a war for the perpetuation of their slavery. Following Judge Mansfield’s decision of 1772 in favour of the slave James Somersett, Britain appeared to represent the possibility of abolition; American independence offered only the certainty of on-going slavery. Nor were loyalist blacks the only ones to see the paradox of the American Revolution. As Samuel Johnson famously pointed out: ‘How is it that we hear the loudest yelps for liberty among the drivers of Negroes?’ In 1792, just under 1200 black loyalists sailed to Sierra Leone, West Africa, under the command of John Clarkson, brother to the abolitionist campaigner Thomas Clarkson. It is the purpose of these articles to look afresh at the settlement there, to see what more can be said about the meaning and significance of Sierra Leone and the loyalists and other blacks who settled there. As has been remarked, these settlers were not of British descent. Who were they, then? Some were native-born Africans, kidnapped and taken as slaves to America. Others were African-American. But how they were regarded, and how they regarded themselves, involves more complex issues, dealing with their history and their determination to achieve self-governance and racial equality during a revolutionary age. Once they had arrived safely in Sierra Leone, William Wilberforce was keen to call them ‘Africans’, a much more dignified term (he argued) than ‘Blacks’ or ‘Negroes’. As a group they identified themselves in their letters and petitions as the ‘Americans’ or ‘the settlers’, or ‘we the Black people that came from Nova Scotia to this place’. At one point, however, when wrangling with the Sierra Leone Company’s directors, they called themselves ‘free British subjects’.2 Their situation was full of contradictions and for the most part fraught with difficulties. These loyalist blacks are at the heart of Schama’s revisionist history, a history which questions the founding principles of the United States. Thus, when it comes to determining which nation owns the bragging rights to freedom, it is not surprising that Rough Crossings favours the British, loyalist side. But Schama also shows how Britain’s offer of freedom was a cloak for military opportunism, a plan to rip out the economic rug from beneath its enemies. Also, as it transpired, liberty for loyalist blacks did not amount to much. For many, freedom meant starving in the freezing forests of Nova Scotia or on the streets of London. It was indeed a rough crossing from one national affiliation to another. Nor did the hypocrisy of Britain’s offer go unremarked. Benjamin Franklin could only scoff at a country which prided itself on setting free a single slave whilst leading the world in the slave trade. Suspicion and scorn would later spread to perceptions of the Sierra Leone venture. With its estuary, deep channels, and well-populated adjacent territories, Sierra Leone had long been a centre for British and other European slave traders. After his initial enthusiasm for Granville Sharp’s ‘Province of Freedom’, Ottobah Cugoano, an ex-slave living in Britain, began to question the motives of a Government which simultaneously sanctioned slavery and sponsored an attempt to abolish it. He asked: ‘Doth a fountain send forth at the same place sweet water and bitter? . . . can it be readily conceived that government would establish a free colony for them nearly on the spot, while it supports its forts and garrisons, to ensnare, merchandize, and...

The impact of heterogeneity on master-slave scheduling

In this paper, we assess the impact of heterogeneity on scheduling independent tasks on master-slave platforms. We assume a realistic one-port model where the master can communicate with a single slave at any time. We target both on-line and off-line scheduling problems, and we focus on simpler instances where all tasks have the same size. While such on-line problems can be solved in polynomial time on homogeneous platforms, we show that there does not exist any optimal deterministic algorithm for heterogeneous platforms. Whether the source of heterogeneity comes from computation speeds, or from communication bandwidths, or from both, we establish lower bounds on the competitive ratio of any deterministic algorithm. We provide such bounds for the most important objective functions: the minimization of the makespan (or total execution time), the minimization of the maximum response time (difference between completion time and release time), and the minimization of the sum of all response times. Altogether, we obtain nine theorems which nicely assess the impact of heterogeneity on on-line scheduling. For off-line scheduling, we prove several result for problems with release dates, either optimality or NP-hardness. These theoretical contributions are complemented on the practical side by the implementation of several heuristics on a small but fully heterogeneous MPI platform. Our results show the superiority of those heuristics which fully take into account the relative capacity of the communication links.

Slavery and the Phenomenology of Torture

Sanford Levinson Slavery and the Phenomenology of Torture THE YEAR 2 0 0 7 WILL BE THE SESQ UICENT ENNIAL OF THE D R E D SC O TT case, perhaps the m ost reviled case in American constitutional history because of its endorsem ent of slavery as constitutionally protected.1 Slavery m ight have been evil, but this did not prevent its full integra­ tion into the warp and woof of American constitutional law, not least because the presum ed overarching good of creating and then m aintain­ ing a union took precedence over alleviating the plight of slaves. Even if m ost people believed that a society w ithout slavery would certainly be better than a society w ith it, they also believed that elim inating slavery was not w orth the risk of dissolution of the union and the presum ed costs attached to that dire possibility. In this context, one m ight recall that Lincoln, in his first inaugural address, went out of his way to reas­ sure the slave states not only that he m eant no harm to their entrenched practices, but also that that he would support a proposed constitutional am endm ent that would in effect guarantee the m aintenance of slav­ ery in perpetuity, at least in the absence of a voluntary decision by the affected states to cease the practice. And it is w orth recalling as well that the Emancipation Proclamation was notorious for failing to free a single slave in the four “union states” where slavery rem ained fully legal—Missouri, Maryland, Kentucky, and Delaware—not least because of fear of switches in loyalty especially by unionist Missouri and Kentucky slaveholders. For many, torture is at least as evil as slavery. Yet we have learned, over the past five years especially, th at for m any Am ericans the social research Vol 74 : No 1: Spring 2007 149 presumed overarching good of m aintaining our national security takes precedence over the plight of those subjected to highly coercive, even tortuous, m eans of interrogation. As w ith slavery, exceedingly prob­ lematic modes of interrogation are being integrated into the warp and woof of our present legal order. And, as w ith slavery, the possibility of term inating the practice is viewed by m any Americans, w hen all is said and done, as potentially m ore harm ful than m aintaining it, w ith all of its acknowledged costs. I believe, though, that the m ost direct reason to look at torture through the prism provided by a 150-year-old case involving chattel slav­ ery is that the m ost fundam ental legal and m oral issues raised by slav­ ery and torture are astonishingly similar. Both ultim ately raise issues of “sovereignty”—that is, the possession of absolute and unconstrained power—and, therefore, the challenge to “sovereignty” that is implicit in any liberal notion of limited government. Both Dred Scott and those who defend torture today ask us if we believe that there are indeed categories of persons who quite literally have “no rights” that the rest of us are “bound to respect.” This article is divided into three sections: The first discusses why, as both a political theorist o f sorts and as a lawyer, I find the issue of torture both compelling and yet intellectually and morally perplexing. The second section is built around my belief that the word “torture” tends basically to be a placeholder, which means that it needs to be filled in with concrete definitions and exemplars that are often lacking. Any serious discussion of the subject—including, obviously, its ethical dimen­ sions—therefore has to confront the reality that there is almost certainly far less agreement than we m ight hope as to what even counts as torture, let alone if there are any circumstances that m ight justify its infliction. This means, am ong other things, th at any real progress w ith regard to establishing acceptable social policies—as distinguished from engaging in polemical argum ent—requires that we engage in an alto­ gether unpleasant and grim task of offering fairly precise notions of w hat counts as...