bluuebunny/crossref_metadata_2025 huggingface dataset:
STATIC AND DYNAMIC BEHAVIOUR OF LAMINATED COMPOSITE BEAMS
Authors: LOJA M. A. RAMOS , BARBOSA J. INFANTE , SOARES C. M. MOTA
Published: July 2002

A higher order shear deformation theory, assuming a non-linear variation for the displacement field, is used to develop a finite element model to predict static and free vibration behaviour of anisotropic multilaminated thick and thin beams. The model is based on a single-layer Lagrangean four-node straight beam element with fourteen degrees of freedom per node. It considers bending into two orthogonal planes, stretching and twisting to enable three-dimensional analysis of frames. The most common cross sections and symmetric and asymmetric lay-ups are studied. The behaviour of the model is tested on thin and thick isotropic and composite beams. Comparisons show that the model is accurate and versatile. The good performance of the present model is evident on the prediction of displacements, normal and transverse stresses and natural frequencies of thin and thick isotropic or anisotropic beam structures.
THE FOUR AVALANCHE FRONTS: A TEST CASE FOR GRANULAR SURFACE FLOW MODELING
Authors: DOUADY STÉPHANE , ANDREOTTI BRUNO , CLADÉ PIERRE , DAERR ADRIAN
Published: July 2002

Granular surface flows have still to be fully modelled. Here, we present the four types of front that can be observed in avalanches. These strongly inhomogeneous and unsteady flows are very sensitive test cases for the different types of model. We show that, at least qualitatively for the moment, the model we propose, based on the analysis of the motion of a single grain and layers of grains, can reproduce the different characteristics of these four fronts.
Extended Horn sets in propositional logic
Authors: Chandru V. , Hooker J. N.
Published: July 2002

The class of Horn clause sets in propositional logic is extended to a larger class for which the satisfiability problem can still be solved by unit resolution in linear time. It is shown that to every arborescence there corresponds a family of extended Horn sets, where ordinary Horn sets correspond to stars with a root at the center. These results derive from a theorem of Chandresekaran that characterizes when an integer solution of a system of inequalities can be found by rounding a real solution in a certain way. A linear-time procedure is provided for identifying “hidden” extended Horn sets (extended Horn but for complementation of variables) that correspond to a specified arborescence. Finally, a way to interpret extended Horn sets in applications is suggested.
A modification of the process interaction world view
Authors: Cota Bruce A. , Sargent Robert G.
Published: July 2002

A formal definition of the process interaction world view is reviewed. A shortcoming of this world view is identified with respect to modularity and encapsulation. A modification of the world view that supports modularity and encapsulation is presented, and its advantages are discussed. It is shown how some recent process-oriented simulation languages support this modified world view. The impact of this modification on parallel simulation is discussed, and the modified world view is briefly compared to the use of object-oriented simulation modeling.
A test problem generator for the Steiner problem in graphs
Authors: Khoury B. N. , Pardalos P. M. , Du D.-Z.
Published: July 2002

In this paper we present a new binary-programming formulation for the Steiner problem in graphs (SPG), which is well known to be NP-hard. We use this formulation to generate test problems with known optimal solutions. The technique uses the KKT optimality conditions on the corresponding quadratically constrained optimization problem.
Las Vegas algorithms for linear and integer programming when the dimension is small
Authors: Clarkson Kenneth L.
Published: July 2002

This paper gives an algorithm for solving linear programming problems. For a problem with n constraints and d variables, the algorithm requires an expected

O(d
2
n) + (log n)O(d)
d/2+O(1)
+ O(d
4
√nlog n)

arithmetic operations, as
n→∞
. The constant factors do not depend on d. Also, an algorithm is given for integer linear programming. Let φ bound the number of bits required to specify the rational numbers defining an input constraint or the objective function vector. Let n and d be as before. Then, the algorithm requires expected

O(2
d
dn + 8
d
d√n ln ln n) + d
O(d)
φ ln n

operations on numbers with

d
O(1)
φ

bits, as
n→∞
, where the constant factors do not depend on d or φ to other convex programming problems. For example, an algorithm for finding the smallest sphere enclosing a set of n points in E
d
has the same time bound.
Building real-time groupware with GroupKit, a groupware toolkit
Authors: Roseman Mark , Greenberg Saul
Published: July 2002

This article presents an overview of GroupKit, a groupware toolkit that lets developers build applications for synchronous and distributed computer-based conferencing. GroupKit was constructed from our belief that programming groupware should be only slightly harder than building functionally similar single-user systems. We have been able to significantly reduce the implementation complexity of groupware through the key features that comprise GroupKit. Aruntime infrastructureautomatically manages the creation, interconnection, and communications of the distributed processes that comprise conference sessions. A set ofgroupware programming abstractionsallows developers to control the behavior of distributed processes, to take action on state changes, and to share relevant data.Groupware widgetslet interface features of value to conference participants to be easily added to groupware applications.Session managers—interfaces that let people create and manage their meetings—are decoupled from groupware applications and are built by developers to accommodate the group's working style. Example GroupKit applications in a variety of domains have been implemented with only modest effort.
Local management of a global resource in a communication network
Authors: Afek Yehuda , Awerbuch Baruch , Plotkin Serge , Saks Michael
Published: July 2002

This paper introduces a new distributed data object called Resource Controller that provides an abstraction for managing the consumption of a global resource in a distributed system. Examples of resources that may be managed by such an object include; number of messages sent, number of nodes participating in the protocol, and total CPU time consumed.

The Resource Controller object is accessed through a procedure that can be invoked at any node in the network. Before consuming a unit of resource at some node, the controlled algorithm should invoke the procedure at this node, requesting a permit or a rejection.

The key characteristics of the Resource Controller object are the constraints that it imposes on the global resource consumption. An (M, W)-Controller guarantees that the total number of permits granted is at mostM; it also ensures that, if a request is rejected, then at leastM—Wpermits are eventually granted, even if no more requests are made after the rejected one.

In this paper, we describe several message and space-efficient implementations of the Resource Controller object. In particular, we present an (M, W)-Controller whose message complexity isO(nlog2nlog(M/(W+ 1)) wherenis the total number of nodes. This is in contrast to theO(nM)message complexity of a fully centralized controller which maintains a global counter of the number of granted permits at some distinguished node and relays all the requests to the node.
Browsing and querying in online documentation
Authors: Hertzum Morten , Frøkjær Erik
Published: July 2002

A user interface study concerning the usage effectiveness of selected retrieval modes was conducted using an experimental text retrieval system, TeSS, giving access to online documentation of certain programming tools. Four modes of TeSS were compared: (1) browsing, (2) conventional boolean retrieval, (3) boolean retrieval based on Venn diagrams, and (4) these three combined. Further, the modes of TeSS were compared to the use of printed manuals. The subjects observed were 87 computing new to them. In the experiment the use of printed manuals is faster and provides answers of higher quality than any of the electronic modes. Therefore, claims about the effectiveness of computer-based text retrieval have to by vary in situations where printed manuals are manageable to the user. Among the modes of TeSS, browsing is the fastest and the one causing the fewest operational errors. On the same two variables, time and operational errors, the Venn diagram mode performs better than conventional boolean retrieval. The combined mode scores worst on the objective performance measures; nonetheless nearly all subject prefer this mode. Concerning the interaction process, the subjects tend to manage the complexities of the information retrieval tasks by issuing series of simple commands and exploiting the interactive capabilities of TeSS. To characterize the dynamics of the interaction process two concepts are introduced; threads and sequences of tactics. Threads in a query sequence describes the continuity during retrieval. Sequences of tactics concern the combined mode and describe how different retrieval modes succeed each other as the retrieval process evolves.
Knowledge abstraction
Authors: Abbott Russell J.
Published: July 2002

One of the primary effects of software abstraction has been to further the notion of computer programs as objects rather than moving programming closer to the problem being solved. Knowledge abstraction, however, allows software to take a significant step toward the problem domain.
The 1984 Olympic Message System: a test of behavioral principles of system design
Authors: Gould John D. , Boies Stephen J. , Levy Stephen , Richards John T. , Schoonard Jim
Published: July 2002

There was more than athletic talent being pressed to peak performance at the 1984 Olympic Games in Los Angeles. Behind the scenes, a multilingual Olympic Message System ran round-the-clock keeping more than 10,000 athletes and officials in contact with families and friends, both far and near.
A database encryption system with subkeys
Authors: Davida George I. , Wells David L. , Kam John B.
Published: July 2002

A new cryptosystem that is suitable for database encryption is presented. The system has the important property of having subkeys that allow the encryption and decryption of fields within a record. The system is based on the Chinese Remainder Theorem.
System R
Authors: Astrahan M. M. , Blasgen M. W. , Chamberlin D. D. , Eswaran K. P. , Gray J. N. , Griffiths P. P. , King W. F. , Lorie R. A. , McJones P. R. , Mehl J. W. , Putzolu G. R. , Traiger I. L. , Wade B. W. , Watson V.
Published: July 2002

System R is a database management system which provides a high level relational data interface. The systems provides a high level of data independence by isolating the end user as much as possible from underlying storage structures. The system permits definition of a variety of relational views on common underlying data. Data control features are provided, including authorization, integrity assertions, triggered transactions, a logging and recovery subsystem, and facilities for maintaining data consistency in a shared-update environment.

This paper contains a description of the overall architecture and design of the system. At the present time the system is being implemented and the design evaluated. We emphasize that System R is a vehicle for research in database architecture, and is not planned as a product.
Decompositions and functional dependencies in relations
Authors: Armstrong W. W. , Deobel C.
Published: July 2002

A general study is made of two basic integrity constraints on relations: functional and multivalued dependencies. The latter are studied via an equivalent concept: decompositions. A model is constructed for any possible combination of functional dependencies and decompositions. The model embodies some decompositions as unions of relations having different schemata of functional dependencies. This suggests a new, stronger integrity constraint, the degenerate decomposition. More generally, the theory demonstrates the importance of using the union operation in database design and of allowing different schemata on the operands of a union. Techniques based on the union lead to a method for solving the problem of membership of a decomposition in the closure of a given set of functional dependencies and decompositions. The concept of antiroot is introduced as a tool for describing families of decompositions, and its fundamental importance for database design is indicated.
A Multistep Generalization of Runge-Kutta Methods With Four or Five Stages
Authors: Butcher John C.
Published: July 2002

To obtain high-order integration methods for ordinary differential equatic which combine to some extent the advantage of Runge-Kutta methods on one hand and line multistep methods on the other, the use of “modified multistep” or “hybrid” method has been proposed by various researchers. In this paper formulas are derived for method which use one extra intermediate point than in the previously published methods so that there are analogues of the fourth-order Runge-Kutta method. A five-stage method of order 7 is already given.
A Method for Constructing Circuit Codes
Authors: Klee Victor
Published: July 2002

A
d
-dimensional circuit code of spread
s
(also called

SIB
s

, code or circuit code of minimum distance
s
) is a simple circuit
Q
in the graph of the
d
-dimensional cube [0, 1]

d

such that any two vertices of
Q
differing in exactly
r
coordinates, with
r
<
s
, can be joined by a path formed from
r
edges of
Q
. Such codes are designed to introduce error detection into certain analog-to-digital conversion systems. Longer codes correspond to increased accuracy of the system, and hence there is interest in determining the maximum length
C
(
d
,
s
) of
d
-dimensional circuit codes of spread
s
. In the present study the author contributes to this problem for even values of
s
by describing a method of combining a code of spread
s
with a suitably related code of spread
s
-1 so as to produce a longer code of spread
s
.
Bounds for the String Editing Problem
Authors: Wong C. K. , Chandra Ashok K.
Published: July 2002

The string editing problem is to determine the distance between two strings as measured by the minimal cost sequence of deletions, insertions, and changes of symbols needed to transform one string into the other. The longest common subsequence problem can be viewed as a special case. Wagner and Fischer proposed an algorithm that runs in time
O
(
nm
), where
n, m
are the lengths of the two strings. In the present paper, it is shown that if the operations on symbols of the strings are restricted to tests of equality, then
O
(
nm
) operations are necessary (and sufficient) to compute the distance.
Integrating geometrical and linguistic analysis for email signature block parsing
Authors: Chen Hao , Hu Jianying , Sproat Richard W.
Published: July 2002

The signature block is a common structured component found in email messages. Accurate identification and analysis of signature blocks is important in many multimedia messaging and information retrieval applications such as email text-to-speech rendering, automatic construction of personal address databases, and interactive message retrieval. It is also a very challenging task, because signature blocks often appear in complex two-dimensional layouts which are guided only by loose conventions. Traditional text analysis methods designed to deal with sequential text cannot handle two-dimensional structures, while the highly unconstrained nature of signature blocks makes the application of two-dimensional grammars very difficult. In this article, we describe an algorithm for signature block analysis which combines two-dimensional structural segmentation with one-dimensional grammatical constraints. The information obtained from both layout and linguistic analysis is integrated in the form of weighted finite-state transducers. The algorithm is currently implemented as a component in a preprocessing system for email text-to-speech rendering.
Abstracting dependencies between software configuration items
Authors: Gunter Carl A.
Published: July 2002

This article studies an abstract model of dependencies between software configuration items based on a theory of concurrent computation over a class of Petri nets called
production
nets. A general theory of build optimizations and their correctness is developed based on a form of abstract interpretation called a
build abstraction
; these are created during a build and are used to optimize subsequent builds. Various examples of such optimizations are discussed. The theory is used to show how properties can be characterized and proved, and how optimizations can be composed and compared.
Monte Carlo methods in theoretical high-energy physics
Authors: Lautrup B.
Published: July 2002

Although lattice field theorists have been able to develop new approaches to the Monte Carlo method and to successfully apply them in Bosonic calculations, faster and larger computers are needed for Fermion-field evaluations.
The programmer as navigator
Authors: Bachman Charles W.
Published: July 2002

This year the whole world celebrates the five-hundredth birthday of Nicolaus Copernicus, the famous Polish astronomer and mathematician. In 1543, Copernicus published his book,
Concerning the Revolutions of Celestial Spheres
, which described a new theory about the relative physical movements of the earth, the planets, and the sun. It was in direct contradiction with the earth-centered theories which had been established by Ptolemy 1400 years earlier.
A history and evaluation of System R
Authors: Chamberlin Donald D. , Astrahan Morton M. , Blasgen Michael W. , Gray James N. , King W. Frank , Lindsay Bruce G. , Lorie Raymond , Mehl James W. , Price Thomas G. , Putzolu Franco , Selinger Patricia Griffiths , Schkolnick Mario , Slutz Donald R. , Traiger Irving L. , Wade Bradford W. , Yost Robert A.
Published: July 2002

System R, an experimental database system, was constructed to demonstrate that the usability advantages of the relational data model can be realized in a system with the complete function and high performance required for everyday production use. This paper describes the three principal phases of the System R project and discusses some of the lessons learned from System R about the design of relational systems and database systems in general.
Achieving specific accuracy in simulation output analysis
Authors: Fishman George S.
Published: July 2002

This paper extends the use of the regenerative property of queueing systems in the analysis of simulation output. In particular, it describes a sequential estimation method which when used with the regenerative property allows results to be obtained with specified statistical accuracy. This method includes a test to check the normality assumption on which the sequential procedure relies. The paper illustrates the method using the empty and idle state as the regenerative state. A second example then describes how using the most frequently entered state as the regenerative state reduces the chance of making a costly error in a preliminary simulation run. The paper also described how a variance reduction method due to Page [9] can be used to obtain a specified accuracy with considerably fewer job completions than are required when no variance reduction technique is applied.
A fast division technique for constant divisors
Authors: Artzy Ehud , Hinds James A. , Saal Harry J.
Published: July 2002

A fast algorithm for division by constant divisors is presented. The method has proved very useful implemented as microcode on a binary machine, and can be adapted directly into hardware. The mathematical foundations of the algorithm are presented as well as some performance measures.
Complex gamma function with error control
Authors: Kuki Hirondo
Published: July 2002

An algorithm to compute the gamma function and the loggamma function of a complex variable is presented. The standard algorithm is modified in several respects to insure the continuity of the function value and to reduce accumulation of round-off errors. In addition to computation of function values, this algorithm includes an object-time estimation of round-off errors. Experimental data with regard to the effectiveness of this error control are presented. A Fortran program for the algorithm appears in the algorithms section of this issue.
Computer generation of gamma random variates with non-integral shape parameters
Authors: Wallace N. D.
Published: July 2002

When the shape parameter,
α
, is integral, generating gamma random variables with a digital computer is straightforward. There is no simple method for generating gamma random variates with non-integral shape parameters. A common procedure is to approximately generate such random variables by use of the so-called probability switch method. Another procedure, which is exact, is due to Jöhnk. This paper presents a rejection method for exactly generating gamma random variables when
α
is greater than 1. The efficiency of the rejection method is shown to be better than the efficiency of Jöhnk's method. The paper concludes that when
α
is non-integral the following mix of procedures yields the best combination of accuracy and efficiency: (1) when
α
is less than 1, use Jöhnk's method; (2) when 1 is less than
α
and
α
is less than 5, use the rejection method; (3) when
α
is greater than 5, use the probability switch method.
A variation on sorting by address calculation
Authors: Jones Bush
Published: July 2002

The principles of address calculation and merging are combined to yield an efficient sorting technique. Detailed flowcharts of the most important program steps are included. The characteristics of the proposed sort are discussed.
The stable marriage problem
Authors: McVitie D. G. , Wilson L. B.
Published: July 2002

The original work of Gale and Shapley on an assignment method using the stable marriage criterion has been extended to find all the stable marriage assignments. The algorithm derived for finding all the stable marriage assignments is proved to satisfy all the conditions of the problem. Algorithm 411 applies to this paper.
Automated complexity analysis based on ordered resolution
Authors: Basin David , Ganzinger Harald
Published: July 2002

We define order locality to be a property of clauses relative to a term ordering. This property generalizes the subformula property for proofs where the terms appearing in proofs can be bounded, under the given ordering, by terms appearing in the goal clause. We show that when a clause set is order local, then the complexity of its ground entailment problem is a function of its structure (e.g., full versus Horn clauses), and the ordering used. We prove that, in many cases, order locality is equivalent to a clause set being saturated under ordered resolution. This provides a means of using standard resolution theorem provers for testing order locality and transforming non-local clause sets into local ones. We have used the Saturate system to automatically establish complexity bounds for a number of nontrival entailment problems relative to complexity classes which include polynomial and exponential time and co-NP.
Numerical Analysis: A fast fourier transform algorithm for real-valued series
Authors: Bergland Glenn D.
Published: July 2002

A new procedure is presented for calculating the complex, discrete Fourier transform of real-valued time series. This procedure is described for an example where the number of points in the series is an integral power of two. This algorithm preserves the order and symmetry of the Cooley-Tukey fast Fourier transform algorithm while effecting the two-to-one reduction in computation and storage which can be achieved when the series is real. Also discussed are hardware and software implementations of the algorithm which perform only (
N
/4) log
2
(
N
/2) complex multiply and add operations, and which require only
N
real storage locations in analyzing each
N
-point record.
Computer experiments in finite algebra
Authors: Maurer Ward Douglas
Published: July 2002

A medium-scale programming system is written in MAD and FAP on the IBM 7094 to manipulate some of the objects of modern algebra: finite groups, maps and sets of maps, subsets and sets of subsets, constant integers and truth-values. Designed to operate in a time-sharing environment, the system can serve as a teacher's aid to the undergraduate student of modern algebra, as well as for the working scientist or engineer wishing to familiarize himself with the subject.
Techniques for automatic tolerance control in linear programming
Authors: Clasen R. J.
Published: July 2002

In this technical note, the numerical steps for the simplex method of linear programming are reviewed and the tolerances needed in the numerical procedure are defined. Objective criteria are given for accomplishing the numerical steps of the method and the calculation of necessary tolerances.
A proposal for character code compatability
Authors: Bemer R. W.
Published: July 2002

The emergence of a single standard from a welter of conflicting precedents depends upon two solutions:

selection or development of an adequate and logical standard,

phasing out (or peaceful coexistence with) the old varieties.

This paper deals with the latter problem and proposes the mechanics for a solution in the area of character codes, as represented by bit combinations.
Parametric temporal logic for “model measuring”
Authors: Alur Rajeev , Etessami Kousha , La Torre Salvatore , Peled Doron
Published: July 2002

We extend the standard model checking paradigm of linear temporal logic, LTL, to a “model measuring” paradigm where one can obtain more quantitative information beyond a “Yes/No” answer. For this purpose, we define a
parametric temporal logic
, PLTL, which allows statements such as “a request
p
is followed in at most
x
steps by a response
q
,” where
x
is a free variable. We show how one can, given a formula ***(

x
1
...,x
k

) of PLTL and a system model
K
satisfies the property ***, but if so find valuations which satisfy various optimality criteria. In particular, we present algorithms for finding valuations which minimize (or maximize) the maximum (or minimum) of all parameters. Theses algorithms exhibit the same PSPACE complexity as LTL model checking. We show that our choice of syntax for PLTL lies at the threshold of decidability for parametric temporal logics, in that several natural extensions have undecidable “model measuring” problems.
Adding range restriction capability to dynamic data structures
Authors: Willard Dan E. , Lueker George S.
Published: July 2002

A database is said to allow range restrictions if one may request that only records with some specified field in a specified range be considered when answering a given query. A transformation is presented that enables range restrictions to be added to an arbitrary dynamic data structure on
n
elements, provided that the problem satisfies a certain decomposability condition and that one is willing to allow increases by a factor of
O
(log
n
) in the worst-case time for an operation and in the space used. This is a generalization of a known transformation that works for static structures. This transformation is then used to produce a data structure for range queries in
k
dimensions with worst-case times of
O
(log

k
n

) for each insertion, deletion, or query operation.
A simplex algorithm whose average number of steps is bounded between two quadratic functions of the smaller dimension
Authors: Adler Ilan , Megiddo Nimrod
Published: July 2002

It has been a challenge for mathematicians to confirm theoretically the extremely good performance of simplex-type algorithms for linear programming. In this paper the average number of steps performed by a simplex algorithm, the so-called
self-dual method
, is analyzed. The algorithm is not started at the traditional point (1, … , l)
T
, but points of the form (1, ϵ, ϵ
2
, …)
T
, with ϵ sufficiently small, are used. The result is better, in two respects, than those of the previous analyses. First, it is shown that the expected number of steps is bounded between two quadratic functions
c
1
(min(
m
,
n
))
2
and
c
2(min(
m
,
n
))
2
of the
smaller
dimension of the problem. This should be compared with the previous two major results in the field. Borgwardt proves an upper bound of
O
(
n
4
m

1/(
n
-1)

) under a model that implies that the zero vector satisfies all the constraints, and also the algorithm under his consideration solves only problems from that particular subclass. Smale analyzes the self-dual algorithm starting at (1, … , 1)
T
. He shows that for any fixed
m
there is a constant
c
(
m
) such the expected number of steps is less than
c
(
m
)(ln
n
)

m
(
m
+1)

; Megiddo has shown that, under Smale's model, an upper bound
C
(
m
) exists. Thus, for the first time, a polynomial upper bound with no restrictions (except for nondegeneracy) on the problem is proved, and, for the first time, a nontrivial lower bound of precisely the same order of magnitude is established. Both Borgwardt and Smale require the input vectors to be drawn from spherically symmetric distributions. In the model in this paper, invariance is required only under certain
Global Virtual Teams
Authors: Dubé Line , Paré Guy
Published: July 2002

Recent interviews with GVT leaders and members offer critical
advice from the trenches regarding the challenges and coping
strategies for collaborating on a global scale.
Behavior-consistent specialization of object life cycles
Authors: Schrefl Michael , Stumptner Markus
Published: July 2002

Object-oriented design methodologies represent the behavior of instances of an object type not merely by a set of operations, but also by providing an overall description on how instances evolve over time. Such a description is often referred to as "object life cycle."Object-oriented systems organize object types in hierarchies in which subtypes inherit and specialize the structure and behavior of their supertypes. Past experience has shown that unrestricted use of inheritance mechanisms leads to system architectures that are hard to understand and to maintain, since arbitrary differences between supertype and subtype are possible. Evidently, this is not a desirable state of affairs and the behavior of a subtype should specialize the behavior of its supertype according to some clearly defined consistency criteria. Such criteria have been formulated in terms of type systems for semantic data models and object-oriented programming languages. But corresponding criteria for the specialization of object life cycles have so far not been thoroughly investigated.This paper defines such criteria in the realm of Object Behavior Diagrams, which have been originally developed for the design of object-oriented databases. Its main contributions are necessary and sufficient rules for checking behavior consistency between object life cycles of object types in specialization hierarchies with multiple inheritance.
Constructing and exploiting linear schedules with prescribed parallelism
Authors: Darte Alain , Schreiber Robert , Rau B. Ramakrishna , Vivien Frédéric
Published: July 2002

We present two new results of importance in code generation for and synthesis of synchronously scheduled parallel processor arrays and multicluster VLIWs. The first is a new practical method for constructing a linear schedule for the iterations of a loop nest that schedules precisely one iteration per cycle on each of a prescribed set of processors. While this problem goes back to the era in which systolic computation was in vogue, it has defied practical solution until now. We provide a closed form solution that enables the enumeration of all such schedules. The second result is a new technique that reduces the cost of code or hardware whose function is to control the flow of data and predicate operations, and to generate memory addresses. The key idea is that by using the mathematical structure of any of the conflict-free schedules we construct, a very shallow recurrence can be developed to inexpensively update these quantities.
Data quality and due process in large interorganizational record systems
Authors: Laudon Kenneth C.
Published: July 2002

As societies have become more dependent on information systems to conduct and record transactions between organizations and individuals, interorganizational computer systems have become a widely used method of coordinating the actions of independent organizations. This article examines the quality of data in one important interorganizational system—the criminal-record system of the United States.
A continuum of disk scheduling algorithms
Authors: Geist Robert , Daniel Stephen
Published: July 2002

A continuum of disk scheduling algorithms, V(
R
), having endpoints V(0) = SSTF and V(1) = SCAN, is defined. V(
R
) maintains a current SCAN direction (in or out) and services next the request with the smallest
effective
distance. The effective distance of a request that lies in the current direction is its physical distance (in cylinders) from the read/write head. The effective distance of a request in the opposite direction is its physical distance plus
R
x (total number of cylinders on the disk). By use of simulation methods, it is shown that this definitional continuum also provides a continuum in performance, both with respect to the mean and with respect to the standard deviation of request waiting time. For objective functions that are linear combinations of the two measures,

μ
w

+

ko
w

, intermediate points of the continuum are seen to provide performance uniformly superior to both SSTF and SCAN. A method of implementing V(
R
) and the results of its experimental use in a real system are presented.
The art of navigating through hypertext
Authors: Nielsen Jakob
Published: July 2002

Hypertext (3), (19), (25) is becoming a popular approach to many computer applications, especially those dealing with the on-line presentation of large amounts of loosely structured information such as on-line documentation or computer-aided learning. There are still many issues concerning hypertext that remain to be resolved, however, many of which are in the user interface area. One of the major usability problems with hypertext is the user's risk of disorientation while navigating the information space. For example, our studies [23] showed that 56 percent of the readers of a document written in one of the most popular commercial hypertext systems agreed fully or partly with the statement I was often confused about ‘where I was. ’

To investigate a number of user interface options in hypertext systems we designed a prototype system in the form of a hypertext report on events at the 1987 hypertext workshop. This system was implemented on an Apple Macintosh with Hypercard as the programming system. (To get a feel for our hypertext system, the reader is encouraged to review Figures 1 to 10 which contain screen dumps of a session with the system and thus constitute a kind of printed demonstration or guided tour.) Hypertext is a very dynamic form of human-computer interaction and can only be fully appreciated in an interactive environment. However, even these figures give a much better understanding of the system than a traditional textual description could give.
Concepts and effectiveness of the cover-coefficient-based clustering methodology for text databases
Authors: Can Fazli , Ozkarahan Esen A.
Published: July 2002

A new algorithm for document clustering is introduced. The base concept of the algorithm, the cover coefficient (CC) concept, provides a means of estimating the number of clusters within a document database and related indexing and clustering analytically. The CC concept is used also to identify the cluster seeds and to form clusters with these seeds. It is shown that the complexity of the clustering process is very low. The retrieval experiments show that the information-retrieval effectiveness of the algorithm is compatible with a very demanding complete linkage clustering method that is known to have good retrieval performance. The experiments also show that the algorithm is 15.1 to 63.5 (with an average of 47.5) percent better than four other clustering algorithms in cluster-based information retrieval. The experiments have validated the indexing-clustering relationships and the complexity of the algorithm and have shown improvements in retrieval effectiveness. In the experiments two document databases are used: TODS214 and INSPEC. The latter is a common database with 12,684 documents.
Introducing Optimality Theory
Authors: Archangeli D. B.
Published: July 2002

▪ Abstract  Optimality theory was introduced in the early 1990s as an alternative model of the organization of natural human language sound systems. This article provides an introduction to the model for the nonlinguist. The basic principles of optimality theory are introduced and explained (GEN, CON, and EVAL). Three important constraint families are explored (Faithfulness, Alignment, and Markedness). Illustrations are provided involving syllabification and vowel harmony in Tibetan and prosodic phonotactics in Tonkawa. The article closes with two general discussions. The first addresses recurring issues in phonological and linguistic analysis and sketches how optimality theory might account for these. The second points out how the explanations arrived at through optimality theory are providing new answers to familiar questions, as well as raising new questions for study.
TRANSPORT OF PROTEINS AND NUCLEIC ACIDS THROUGH PLASMODESMATA
Authors: Ghoshroy Soumitra , Lartey Robert , Sheng Jinsong , Citovsky Vitaly
Published: July 2002

▪ Abstract  Despite a potentially key role in cell-to-cell communication, plant intercellular connections—the plasmodesmata—have long been a biological “black box.” Little is known about their protein composition, regulatory mechanisms, or transport pathways. However, recent studies have shed some light on plasmodesmal function. These connections have been shown to actively traffic proteins and protein–nucleic acid complexes between plant cells. This review describes these transport processes—specifically, cell-to-cell movement of plant viruses as well as endogenous cellular proteins—and discusses their possible mechanism(s). For comparison and to provide a broader perspective on the plasmodesmal transport process, the current model for nuclear import, the only other known example of transport of large proteins and protein–nucleic acid complexes through a membrane pore, is summarized. Finally, the function of plasmodesmata as communication boundaries within plant tissue is discussed.
CYANOBACTERIAL CIRCADIAN RHYTHMS
Authors: Golden Susan S. , Ishiura Masahiro , Johnson Carl Hirschie , Kondo Takao
Published: July 2002

▪ Abstract  Evidence from a number of laboratories over the past 12 years has established that cyanobacteria, a group of photosynthetic eubacteria, possess a circadian pacemaker that controls metabolic and genetic functions. The cyanobacterial circadian clock exhibits the three intrinsic properties that have come to define the clocks of eukaryotes: The timekeeping mechanism controls rhythms that show a period of about 24 h in the absence of external signals, the phase of the rhythms can be reset by light/dark cues, and the period is relatively insensitive to temperature. The promise of cyanobacteria as simple models for elucidating the biological clock mechanism is being fulfilled, as mutants affected in period, rhythm generation, and rhythm amplitude, isolated through the use of real time reporters of gene expression, have implicated genes involved in these aspects of the clock.
Reference Frames in Astronomy
Authors: Johnston K. J. , de Vegt Chr.
Published: July 2002

▪ Abstract  Advances in wide-angle astrometric measurements of three to four orders of magnitude in the last thirty years have resulted in a redefinition of the fundamental astronomical reference frame. This new frame, the International Celestial Reference Frame (ICRF), is based on the radio positions of 212 compact extragalactic radio sources. The ICRF defines the direction of the axes of the International Celestial Reference System (ICRS) with a precision of approximately 20 μas. At optical wavelengths, the Hipparcos catalog is the realization of this frame. The precision with which the ICRF is now determined requires that the ICRS models for precession, nutation, and others, be revised. Increases in the precision of measurements from astrometric space missions will further improve the celestial reference frame and may require its redefinition within the next ten years. These improvements will again challenge the models for the celestial reference system.
Charting the Fate of the “Good Cholesterol”: Identification and Characterization of the High-Density Lipoprotein Receptor SR-BI
Authors: Krieger Monty
Published: July 2002

▪ Abstract  Risk for cardiovascular disease due to atherosclerosis increases with increasing concentrations of low-density lipoprotein (LDL) cholesterol and is inversely proportional to the levels of high-density lipoprotein (HDL) cholesterol. The receptor-mediated control of plasma LDL levels has been well understood for over two decades and has been a focus for the pharmacologic treatment of hypercholesterolemia. In contrast, the first identification and characterization of a receptor that mediates cellular metabolism of HDL was only recently reported. This receptor, called scavenger receptor class B type I (SR-BI), is a fatty acylated glycoprotein that can cluster in caveolae-like domains on the surfaces of cultured cells. SR-BI mediates selective lipid uptake from HDL to cells. The mechanism of selective lipid uptake is fundamentally different from that of classic receptor-mediated endocytic uptake via coated pits and vesicles (e.g. the LDL receptor pathway) in that it involves efficient receptor-mediated transfer of the lipids, but not the outer shell proteins, from HDL to cells. In mice, SR-BI plays a key role in determining the levels of plasma HDL cholesterol and in mediating the regulated, selective delivery of HDL-cholesterol to steroidogenic tissues and the liver. Significant alterations in SR-BI expression can result in cardiovascular and reproductive disorders. SR-BI may play a similar role in humans; thus, modulation of its activity may provide the basis of future approaches to the treatment and prevention of atherosclerotic disease.
Molecular Bases of Circadian Rhythms
Authors: Harmer Stacey L. , Panda Satchidananda , Kay Steve A.
Published: July 2002

▪ Abstract  Circadian rhythms are found in most eukaryotes and some prokaryotes. The mechanism by which organisms maintain these roughly 24-h rhythms in the absence of environmental stimuli has long been a mystery and has recently been the subject of intense research. In the past few years, we have seen explosive progress in the understanding of the molecular basis of circadian rhythms in model systems ranging from cyanobacteria to mammals. This review attempts to outline these primarily genetic and biochemical findings and encompasses work done in cyanobacteria, Neurospora, higher plants, Drosophila, and rodents. Although actual clock components do not seem to be conserved between kingdoms, central clock mechanisms are conserved. Somewhat paradoxically, clock components that are conserved between species can be used in diverse ways. The different uses of common components may reflect the important role that the circadian clock plays in adaptation of species to particular environmental niches.
Converging Paths Leading to the Role of the Oceans in Climate Change
Authors: Broecker Wallace S.
Published: July 2002

▪ Abstract  A young man adrift, I was rescued by Paul Gast, a college classmate, and sent off to Columbia's Lamont Geological Observatory as a summer intern. As it turns out, I am still there. During this 47-year sojourn, I have been a participant in the enormous expansion of the field of isotope geochemistry. I experienced the golden age when so many plums awaited picking that we, the pioneers, gorged ourselves with exciting discovery. Being at what is now called Lamont-Doherty Earth Observatory put me at the center of many of the developments that changed forever the Earth Sciences. It also made me part of the great challenge associated with the drive to replace the exploitative mode that characterized the Industrial Revolution with what is often referred to as the sustainable mode. In the following pages I recount my path from confused youth to the globe-encircling oceanic “conveyor belt.”
ECOLOGICAL CONSIDERATIONS FOR THE ENVIRONMENTAL IMPACT EVALUATION OF RECOMBINANT BACULOVIRUS INSECTICIDES
Authors: Richards Andrew , Matthews Marcus , Christian Peter
Published: July 2002

▪ Abstract  The history of baculoviruses in insect control and the current status of recombinant baculovirus (recBV) insecticides in the laboratory and the field are briefly outlined. A conceptual model for impact evaluation is described that distinguishes between scientific impact evaluation and regulatory risk assessment. Its components are identified and reviewed in the light of existing ecological theory and experimental study under the categories of impact identification, exposure identification, and impact evaluation. Impact identification aims to identify species and populations sensitive to direct or indirect impacts by a recBV. Exposure identification examines how susceptible populations may be exposed to a recBV. Impact evaluation combines these data to predict the potential for recBV impacts in the environment.
BIONOMICS OF THE ANTHOCORIDAE
Authors: Lattin John D.
Published: July 2002

▪ Abstract  The family Anthocoridae (Hemiptera:Heteroptera) contains between 400 and 600 species distributed worldwide, chiefly on the continents but also on oceanic islands. They are small (1.4–4.5 mm) and common to a wide variety of habitats. Many are found in cryptic habitats such as galls, several widespread genera are surface feeders on small arthropods (Anthocoris, Orius, and Tetraphleps), and others can be found in ant nests and, especially, under bark. Wing polymorphism is common in this family, often associated with the cryptic habit. Most known species are predaceous, though some take plant food as well (e.g. Orius insidiosus, Orius pallidicornis). A few of these are believed to be entirely phytophagous (Paratriphleps laeviusculus). Their small size and often generalized feeding habits have resulted in about 30 introduced species, mostly accidental. A few have been introduced deliberately as biological control agents (Anthocoris spp., Montandoniola moraguesi, O. insidiosus, Orius tristicolor, and Tetraphleps spp.). Most nonindigenous species seem to have been distributed as a result of human activities, especially commerce. The predaceous habits of many Anthocoridae have attracted the attention of researchers who work in agroecosystems. Integrated pest management programs often include these predators, which has given us greater knowledge about these species than those found in natural ecosystems. Exciting discoveries about the attractiveness to these bugs of certain volatile plant and arthropod compounds are opening new areas of investigation into their chemical ecology. The reactions of these tiny predators will surely become better understood as a result.