Classical List Research Articles

Tighter approximation bounds for LPT scheduling in two special cases

Q | | C max denotes the problem of scheduling n jobs on m machines of different speeds such that the makespan is minimized. In the paper two special cases of Q | | C max are considered: case I, when m − 1 machine speeds are equal, and there is only one faster machine; and case II, when machine speeds are all powers of 2 (2- divisible machines). Case I has been widely studied in the literature, while case II is significant in an approach to design so called monotone algorithms for the scheduling problem. We deal with the worst case approximation ratio of the classic list scheduling algorithm ‘Largest Processing Time (LPT)’. We provide an analysis of this ratio Lpt / Opt for both special cases: For ‘one fast machine’, a tight bound of ( 3 + 1 ) / 2 ≈ 1.3660 is given. For 2-divisible machines, we show that in the worst case 1.3673 < Lpt / Opt < 1.4 . Besides, we prove another lower bound of 955 / 699 > ( 3 + 1 ) / 2 when LPT breaks ties arbitrarily. To our knowledge, the best previous lower and upper bounds were ( 4 / 3 , 3 / 2 − 1 / 2 m ] in case I [T. Gonzalez, O.H. Ibarra, S. Sahni, Bounds for LPT schedules on uniform processors, SIAM Journal on Computing 6 (1) (1977) 155–166], respectively [ 4 / 3 − 1 / 3 m , 3 / 2 ] in case II [R.L. Graham, Bounds on multiprocessing timing anomalies, SIAM Journal on Applied Mathematics 17 (1969) 416–429; A. Kovács, Fast monotone 3-approximation algorithm for scheduling related machines, in: Proc. 13th Europ. Symp. on Algs. (ESA), in: LNCS, vol. 3669, Springer, 2005, pp. 616–627]. Moreover, Gonzalez et al. conjectured the lower bound 4/3 to be tight in the ‘one fast machine’ case [T. Gonzalez, O.H. Ibarra, S. Sahni, Bounds for LPT schedules on uniform processors, SIAM Journal on Computing 6 (1) (1977) 155–166].

Dessins d’enfants and differential equations

We state and solve a discrete version of the classical Riemann-Hilbert problem. In particular, we associate a Riemann-Hilbert problem to every dessin d'enfants. We show how to compute the solution for a dessin that is a tree. This amounts to finding a Fuchsian differential equation satisfied by the local inverses of a Shabat polynomial. We produce a uni- versal annihilating operator for the inverses of a generic polynomial. We classify those plane trees that have a representation by Mobius transformations and those that have a linear rep- resentation of dimension at most two. This yields an analogue for trees of Schwarz's classical list, that is, a list of those plane trees whose Riemann-Hilbert problem has a hypergeometric solution of order at most two.

Modelling higher-order dual nondeterminacy

We investigate models for programming and specifying in which higher-order functions and nondeterminacy (both demonic and angelic) coexist. The models are built using predicate transformers, binary multirelations, state transformers, and free lattices over a poset. We show there exist suitable models in each approach, and that they are isomorphic. The models support an algebra of nondeterminacy which we use to prove that the classical list fusion law holds even in the presence of nondeterminacy.

Heuristic evaluation applied to library web services

PurposeThe purpose of the paper is to present usability heuristics for the evaluation of public library web services.Design/methodology/approachHeuristics for library services are based on Nielsen's classical list of heuristics and results of previous usability research of library web services. A total of 15 public library web sites were evaluated on the basis of these applied heuristics. One part of the study was supported through usability tests. The results of these studies were utilized to evaluate the applied heuristics.FindingsThe applied heuristics are divided into three categories: heuristics critical from the usability viewpoint; heuristics concerning major problems; and heuristics connected to minor usability problems but still important and concerning conventions of web design. The use of the heuristics and the results they give are evaluated to provide a basis for their use in future.Research limitations/implicationsThe applied heuristics lists have been tested in two different studies, and the combined list based on them has so far been utilized in practical evaluation, but has not been formally tested.Practical implicationsThe heuristics for library web services presented in this paper can be applied to usability evaluation of public library web services.Originality/valueLibrary web sites should be user friendly, because the services are meant for all citizens. The applied heuristics for public library web services provide a starting point for usability evaluation that can be continued with other methods.

Japanese journals also have their citation classics in occupational medicine

Japanese journals also have their citation classics in occupational medicine

Exploiting a list of protein sequences

We describe a software program to help exploit a database of aligned protein sequences. In addition to the classical lists of sequences, a graphical representation is used to get a better overview of the information. As natural parameters, the type of amino acid and sequence position are used. Various plots or 3D representations are then updated. Examples are shown based on globin sequences from various species and on the abnormal human hemoglobins. The software should be of interest to protein engineers who need to know what variants are already known.

Joint scheduling for optical grid applications

Optical networking technologies are expected to play an important role in creating an efficient infrastructure for supporting advanced grid applications. Since both the scheduling methods in grid computing and optical networks are limited to be directly used to achieve optical grid scheduling, we propose a new, to the best of our knowledge, joint scheduling model by extending the classic list scheduling algorithm to achieve communication contention aware task scheduling for the optical grid applications. An effective adaptive routing scheme is also proposed to improve the performance of the extended list scheduling. The impacts of different routing schemes on the extended list scheduling are comparatively investigated by simulations.

A Web-Based Systematic Review on Traumatic Spinal Cord Injury Comparing the "Citation Classics" with the Consumers' Perspectives

Although the citation index of an article is not a direct measure of its quality or importance, it is a measure of recognition that may suggest its impact on the scientific community. This study was undertaken to examine the characteristics of the top 100 most frequently cited articles (so-called "citation classics") on traumatic spinal cord injury (SCI) that were published between 1986 and 2003, and to compare this selected professional literature with the consumers' perspective on the key issues in SCI research. The 100 top-cited articles on traumatic SCI were identified using the Internet database of the Science Citation Index Expanded and the Web of Science with the terms "spinal cord injury" and "spinal cord injuries." Meeting abstracts, letters, and editorials were excluded. No language restriction was applied. From a consumers' perspective, the areas of greatest interest for people with SCI as reported in two previous large-scale surveys include motor function, bowel and bladder control, sexual function, and pain. The final list of citation classics on traumatic SCI included 82 original articles and 18 article reviews, which were cited 146 times on average. Topics on basic science (63%) were more frequent than clinical studies (37%). The years of publication were distributed in a bell-shape curve with a peak between 1992 and 1994. North American and European centers (99%) led the list of the citation classics. Most of the top 100 most frequently cited articles on traumatic SCI (63%) explicitly focused on at least one of the topics of greatest interest to individuals with SCI. Motor function was the leading topic in the matching list between professional literature and consumers' perspective. This bibliometric analysis, for the first time, identifies the key features of the citation classics on traumatic SCI between 1986 and 2003, a period that represents one of an unprecedented increase in knowledge in this field. The 100 top-cited peer-reviewed articles have been predominantly focused on basic science SCI research indicating a need for greater bench-to-bedside translational studies in SCI research. Although the body of this top-cited professional literature mostly matches with the consumers' perspective, most of this research has been focused on motor function assessment and recovery following SCI.

Online Certification Status Verification with a Red-Black Hash Tree

Certificate revocation is a critical issue for a practical, public-key infrastructure. A new efficient revocation protocol using a one-way hash tree structure (instead of the classical list structure, which is known as a standard for revocation) was proposed and examined to reduce communication and computation costs. A tree approach, however, may run in O(n) time, in the worst case, i.e., when all the entries are sorted in descending order. A red-black tree is a binary sorted tree, with one extra bit per node, which is used for balancing the tree and guarantees that search and insertion operations take O(logn), even in the worst case. In this paper, we propose a binary red-black hash tree for certificate revocation and prove that it reduces costs more than any other tree balancing approache. We also compare the estimated communication and computation cost reductions of the red-black hash tree to those of the conventional binary search tree.

The American classics: a personal essay

How is a classic book to be defined? How much time must elapse before a work may be judged a classic? And among all the works of American literature, which deserve the designation? In this provocative new book Denis Donoghue essays to answer these questions. He presents his own short list of relative classics--works whose appeal may not be universal but which nonetheless have occupied an important place in our culture for more than a century. These books have survived the abuses of time--neglect, contempt, indifference, willful readings, excesses of praise, and hyperbole. Donoghue bestows the term classic on just five American works: Melville's Moby-Dick, Hawthorne's The Scarlet Letter, Thoreau's Walden, Whitman's Leaves of Grass, and Twain's Adventures of Huckleberry Finn. Examining each in a separate chapter, he discusses how the writings have been received and interpreted, and he offers his own contemporary readings, suggesting, for example, that in the post--9/11 era, Moby-Dick may be rewardingly read as a revenge tragedy. Donoghue extends an irresistible invitation to open the pages of these American classics again, demonstrating with wit and acuity how very much they have to say to us now.

Communication contention in task scheduling

Task scheduling is an essential aspect of parallel programming. Most heuristics for this NP-hard problem are based on a simple system model that assumes fully connected processors and concurrent interprocessor communication. Hence, contention for communication resources is not considered in task scheduling, yet it has a strong influence on the execution time of a parallel program. This paper investigates the incorporation of contention awareness into task scheduling. A new system model for task scheduling is proposed, allowing us to capture both end-point and network contention. To achieve this, the communication network is reflected by a topology graph for the representation of arbitrary static and dynamic networks. The contention awareness is accomplished by scheduling the communications, represented by the edges in the task graph, onto the links of the topology graph. Edge scheduling is theoretically analyzed, including aspects like heterogeneity, routing, and causality. The proposed contention-aware scheduling preserves the theoretical basis of task scheduling. It is shown how classic list scheduling is easily extended to this more accurate system model. Experimental results show the significantly improved accuracy and efficiency of the produced schedules.

Innovation and sustainability in mechanical design through materials selection

Materials selection is a difficult and subtle task, due to the immense number of different available materials. Dealing with such exhaustive information was made possible through the systematization of the materials by their properties. Systematization provides enlarging the classical list of materials and offers new possibilities, facing innovation and sustainability. A practical example concerning the selection of materials to substitute poly vinyl chloride (PVC) in automobile interiors, is studied. Substitution intends avoiding health damage and environmental burden due to PVC, meeting, at the same time, the innovation quisites and the sustainability exigencies. Selection was made by applying the methodologies developed by Ashby and co-workers. Natural materials cork and wood were selected.

Citation Classics in Anesthetic Journals

The number of citations an article receives after its publication reflects its recognition in the scientific community. In the present study, therefore, we identified and examined the characteristics of the top 100 most frequently cited articles published in anesthetic journals. These articles were identified using the database of the Science Citation Index Expanded (SCI-EXPANDED, 1945 to present) and the Web of SCIENCE(R). The most-cited article received 707 citations and the least cited article received 197 citations, with a mean of 283 citations per article. These citation classics were published between 1954 and 1997 in 5 high-impact anesthetic journals, led by Anesthesiology (73 articles) followed by Anesthesia & Analgesia (10), British Journal of Anesthesia (10), Anesthesia (6), and Acta Anaesthesiologica Scandinavica (2). Seventy-eight articles were original publications, 22 were review articles, and one was an editorial. They originated from nine countries, with the United States contributing 70 articles. Within the United States, California leads the list of citation classics with 25 articles. Twenty-nine persons authored two or more of the top-cited articles. The main topics covered by the top-cited articles are pharmacology, volatile anesthetics, circulation, regional anesthesia, and lung physiology. This analysis of citation rates allows for the recognition of seminal advances in anesthesia and gives a historic perspective on the scientific progress of this specialty. We performed a citation analysis to identify important contributions and contributors to the anesthetic literature. These classic articles have influenced many people and have brought to our attention the many important advances in anesthesia made during the last 50 yr.

Essential Papers on Post Traumatic Stress Disorder

Back to table of contents Previous article Next article Book Forum: Trauma and DissociationFull AccessEssential Papers on Post Traumatic Stress DisorderROBERT J. URSANO, M.D., ROBERT J. URSANOSearch for more papers by this author, M.D., Bethesda, Md.Published Online:1 Aug 2000https://doi.org/10.1176/appi.ajp.157.8.1358AboutSectionsView EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail An editor immediately runs a substantial risk when titling a book “Essential Papers on…,” since readers will expect to see their favorite classics. As I began perusing Essential Papers on Post Traumatic Stress Disorder, I had in mind, of course, my own list of essential and classic papers that I hoped to see in the volume. The problem is that lists of essential papers often only overlap in some areas. This is true here. One would expect to see Lindemann’s paper on symptoms of acute grief, Pynoos and Eth’s paper on children witnessing violence, Shore’s study of Mount St. Helens, and at least one paper by Bonnie Green and Jack Lindy. These are present. Similarly, Lifton and Olson’s paper on the Buffalo Creek disaster, published in 1976, was a major contribution to our recognition of the impact on health and community function of the threat to one’s life and exposure to death. Eitinger’s work on concentration camp victims represents an entire genre of publications on which the studies of posttraumatic stress disorder (PTSD) have been built. However, it is surprising to find a paper on eye movement desensitization in such a volume. What makes a paper essential, what makes it a classic, is much in the eye of the beholder.Dr. Horowitz has put together an interesting collection of papers, many of which are important readings for those interested in individual responses to traumatic events, and, yes, some are essential readings. Dr. Horowitz has been a major contributor himself in this area, and his paper describing intrusive and avoidant symptoms, which led to the Impact of Events Scale—perhaps the most widely used instrument in studies of trauma—is a superb example of an essential reading. The volume is slanted toward individual responses with a substantial emphasis on dissociation. In addition, there are a few epidemiological studies and a few papers on war-related trauma.The volume is broken into three parts, which, with some detective work, the reader can identify as related to diagnosis, explanation, and treatment of PTSD. Twenty-eight papers are included, three from Horowitz and his group. Previous volumes in this series have included Essential Papers on Addiction(1), Essential Papers on Obsessive-Compulsive Disorder(2), and Essential Papers on Short-Term Dynamic Therapy(3), as well as others. The reader will find a number of papers of interest and, without doubt, several that are on every person’s essential and classic list. Others can be skimmed or avoided, and occasionally an undiscovered jewel will be found by the diligent reader. This book will primarily find value for teachers who desire a ready reference of papers on PTSD and for those who want to have a ready source of these specific papers in a single volume.Edited by Mardi J. Horowitz, M.D. New York, New York University Press, 1999, 550 pp., $75.00; $27.50 (paper).

On-line scheduling with setup costs

This paper deals with an on-line scheduling problem where tasks belong to a given set of c task types and are to be assigned to one of the m machines in order to minimize the maximum completion time. If a task of a certain type is assigned to a machine that has just completed the execution of a task of the same type, then it can be processed immediately. Otherwise, there is a setup time associated with switching the machine to a different task type. A suitable version of the classical List Scheduling algorithm is analyzed. A new algorithm is also proposed and an upper bound on its competitive ratio is introduced. Finally, lower bound on the competitive ratio for any on-line algorithm is derived.

A [ITAL]Hipparcos[/ITAL] Census of the Nearby OB Associations

A comprehensive census of the stellar content of the OB associations within 1 kpc from the Sun is presented, based on Hipparcos positions, proper motions, and parallaxes. It is a key part of a long-term project to study the formation, structure, and evolution of nearby young stellar groups and related star-forming regions. OB associations are unbound moving groups, which can be detected kinematically because of their small internal velocity dispersion. The nearby associations have a large extent on the sky, which traditionally has limited astrometric membership determination to bright stars (V 6 mag), with spectral types earlier than ~B5. The Hipparcos measurements allow a major improvement in this situation. Moving groups are identified in the Hipparcos Catalog by combining de Bruijne's refurbished convergent point method with the Spaghetti method of Hoogerwerf & Aguilar. Astrometric members are listed for 12 young stellar groups, out to a distance of ~650 pc. These are the three subgroups Upper Scorpius, Upper Centaurus Lupus, and Lower Centaurus Crux of Sco OB2, as well as Vel OB2, Tr 10, Col 121, Per OB2, α Persei (Per OB3), Cas–Tau, Lac OB1, Cep OB2, and a new group in Cepheus, designated as Cep OB6. The selection procedure corrects the list of previously known astrometric and photometric B- and A-type members in these groups and identifies many new members, including a significant number of F stars, as well as evolved stars, e.g., the Wolf-Rayet stars γ2 Vel (WR 11) in Vel OB2 and EZ CMa (WR 6) in Col 121, and the classical Cepheid δ Cep in Cep OB6. Membership probabilities are given for all selected stars. Monte Carlo simulations are used to estimate the expected number of interloper field stars. In the nearest associations, notably in Sco OB2, the later-type members include T Tauri objects and other stars in the final pre–main-sequence phase. This provides a firm link between the classical high-mass stellar content and ongoing low-mass star formation. Detailed studies of these 12 groups, and their relation to the surrounding interstellar medium, will be presented elsewhere. Astrometric evidence for moving groups in the fields of R CrA, CMa OB1, Mon OB1, Ori OB1, Cam OB1, Cep OB3, Cep OB4, Cyg OB4, Cyg OB7, and Sct OB2, is inconclusive. OB associations do exist in many of these regions, but they are either at distances beyond ~500 pc where the Hipparcos parallaxes are of limited use, or they have unfavorable kinematics, so that the group proper motion does not distinguish it from the field stars in the Galactic disk. The mean distances of the well-established groups are systematically smaller than the pre-Hipparcos photometric estimates. While part of this may be caused by the improved membership lists, a recalibration of the upper main sequence in the Hertzsprung-Russell diagram may be called for. The mean motions display a systematic pattern, which is discussed in relation to the Gould Belt. Six of the 12 detected moving groups do not appear in the classical list of nearby OB associations. This is sometimes caused by the absence of O stars, but in other cases a previously known open cluster turns out to be (part of) an extended OB association. The number of unbound young stellar groups in the solar neighborhood may be significantly larger than thought previously.

Exotic holonomy on moduli spaces of rational curves

Bryant [3] proved the existence of torsion free connections with exotic holonomy, i.e., with holonomy that does not occur on the classical list of Berger [1]. These connections occur on moduli spaces Y of rational contact curves in a contact threefold W. Therefore, they are naturally contained in the moduli space Z of all rational curves in W. We construct a connection on Z whose restriction to Y is torsion free. However, the connection on Z has torsion unless both Y and Z are flat. This answers a question of Bryant as to whether the GL(2, C) × SL(2, C)-structures which arise from such a moduli space Z always admit a torsion free connection in the negative. We also show the existence of a new exotic holonomy which is a certain six-dimensional representation of SL(2, C) × SL(2, C). We show that every regular H 3-connection (cf. [3]) is the restriction of a unique connection with this holonomy.

On homogeneous connections with exotic holonomy

In Proc. Symp. Pure Math.53 (1991), 33–88, Bryant gave examples of torsion free connections on four-manifolds whose holonomy is exotic, i.e. is not contained on Berger's classical list of irreducible holonomy representations. The holonomy in Bryant's examples is the irreducible four-dimensional representation of S1(2, #x211D;) (G1(2, #x211D;) resp.) and these connections are called H3-connections (G3-connections resp.).

Scheduling precedence constrained task graphs with non-negligible intertask communication onto multiprocessors

The multiprocessor scheduling problem is the problem of scheduling the tasks of a precedence constrained task graph (representing a parallel program) onto the processors of a multiprocessor in a way that minimizes the completion time. Since this problem is known to be NP-hard in the strong sense in all but a few very restricted eases, heuristic algorithms are being developed which obtain near optimal schedules in a reasonable amount of computation time. We present an efficient heuristic algorithm for scheduling precedence constrained task graphs with nonnegligible intertask communication onto multiprocessors taking contention in the communication channels into consideration. Our algorithm for obtaining satisfactory suboptimal schedules is based on the classical list scheduling strategy. It simultaneously exploits the schedule-holes generated in the processors and in the communication channels during the scheduling process in order to produce better schedules. We demonstrate the effectiveness of our algorithm by comparing with two competing heuristic algorithms available in the literature. >

A fixed point approach to parallel discrete event simulation

Discrete event simulation is viewed as solving a fixed point problem whose unknowns are infinite histories or streams of event and time information. Stream domains provide two notions of convergence, which correspond to the usual categorization of simulation methods. Metric convergence leads to optimistic parallel simulation (the classic event list mechanism turns out to be a specialization), and convergence in the sense of partial orders leads to conservative parallel simulation.