How closely can a personal computer clock track the UTC timescale via the Internet?

Abstract: Nowadays many software packages allow you to keep the clock of your personal computer synchronized to time servers spread over the internet. We present how a didactic laboratory can evaluate, in a statistical sense, the minimum synch error of this process (the other extreme, the maximum, is guaranteed by the code itself). The measurement set-up utilizes the global positioning system satellite constellation in 'common view' between two similar timing stations: one acts as a time server for the other, so the final timing difference at the second station represents the total synch error through the internet. Data recorded over batches of 10000 samples show a typical RMS value of 35 ms. This measurement configuration allows students to obtain a much better understanding of the synch task and pushes them, at all times, to look for an experimental verification of data results, even when they come from the most sophisticated 'black boxes' now readily available off the shelf


Knowledge acquisition for expert systems in accounting and financial problem domains

Abstract: Since the mid-1980s, expert systems have been developed for a variety of problems in accounting and finance. The most commonly cited problems in developing these systems are the unavailability of the experts and knowledge engineers and difficulties with the rule extraction process. Within the field of artificial intelligence, this has been called the 'knowledge acquisition' (KA) problem and has been identified as a major bottleneck in the expert system development process. Recent empirical research reveals that certain KA techniques are significantly more efficient than others in helping to extract certain types of knowledge within specific problem domains. This paper presents a mapping between these empirical studies and a generic taxonomy of expert system problem domains. To accomplish this, we first examine the range of problem domains and suggest a mapping of accounting and finance tasks to a generic problem domain taxonomy. We then identify and describe the most prominent KA techniques employed in developing expert systems in accounting and finance. After examining and summarizing the existing empirical KA work, we conclude by showing how the empirical KA research in the various problem domains can be used to provide guidance to developers of expert systems in the fields of accounting and finance

knowledge acquisition
expert systems
accounting
finance
rule extraction process
artificial intelligence
problem domain taxonomy


A component-based software configuration management model and its supporting system

Abstract: Software configuration management (SCM) is an important key technology in software development. Component-based software development (CBSD) is an emerging paradigm in software development. However, to apply CBSD effectively in real world practice, supporting SCM in CBSD needs to be further investigated. In this paper, the objects that need to be managed in CBSD is analyzed and a component-based SCM model is presented. In this model, components, as the integral logical constituents in a system, are managed as the basic configuration items in SCM, and the relationships between/among components are defined and maintained. Based on this model, a configuration management system is implemented


Games machines play

Abstract: Individual rationality, or doing what is best for oneself, is a standard model used to explain and predict human behavior, and von Neumann-Morgenstern game theory is the classical mathematical formalization of this theory in multiple-agent settings. Individual rationality, however, is an inadequate model for the synthesis of artificial social systems where cooperation is essential, since it does not permit the accommodation of group interests other than as aggregations of individual interests. Satisficing game theory is based upon a well-defined notion of being good enough, and does accommodate group as well as individual interests through the use of conditional preference relationships, whereby a decision maker is able to adjust its preferences as a function of the preferences, and not just the options, of others. This new theory is offered as an alternative paradigm to construct artificial societies that are capable of complex behavior that goes beyond exclusive self interest

individual rationality
human behavior
game theory
multiple-agent
artificial social systems
cooperation
conditional preference relationships
artificial societies
self interest
decision theory
group rationality


Fractional differentiation in passive vibration control

Abstract: From a single-degree-of-freedom model used to illustrate the concept of vibration isolation, a method to transform the design for a suspension into a design for a robust controller is presented. Fractional differentiation is used to model the viscoelastic behaviour of the suspension. The use of fractional differentiation not only permits optimisation of just four suspension parameters, showing the 'compactness' of the fractional derivative operator, but also leads to robustness of the suspension's performance to uncertainty of the sprung mass. As an example, an engine suspension is studied

fractional differentiation
passive vibration control
vibration isolation
suspension
robust controller
viscoelastic behaviour
sprung mass
engine suspension


A fractional-flow model of serial manufacturing systems with rework and its reachability and controllability properties

Abstract: A dynamic fractional-flow model of a serial manufacturing system incorporating rework is considered. Using some results on reachability and controllability of positive linear systems the ability of serial manufacturing systems with rework to "move in space", that is their reachability and controllability properties, are studied. These properties are important not only for optimising the performance of the manufacturing system, possibly off-line, but also to improve its functioning by using feedback control online

serial manufacturing systems
rework
reachability
controllability
dynamic fractional-flow model
positive linear systems
performance optimisation
feedback control


Syndicators turn to the enterprise

Abstract: Syndicators have started reshaping offerings, products, and services towards the marketplace that was looking for enterprise-wide content syndication technology and service. Syndication companies are turning themselves into infrastructure companies. Many syndication companies are now focusing their efforts on enterprise clients instead of the risky dot coms


Learning nonregular languages: a comparison of simple recurrent networks and LSTM

Abstract: Rodriguez (2001) examined the learning ability of simple recurrent nets (SRNs) (Elman, 1990) on simple context-sensitive and context-free languages. In response to Rodriguez's (2001) article, we compare the performance of simple recurrent nets and long short-term memory recurrent nets on context-free and context-sensitive languages

nonregular language learning
recurrent neural networks
LSTM
context-sensitive languages
context-free languages
performance
short-term memory recurrent nets


Orthogonal decompositions of complete digraphs

Abstract: A family G of isomorphic copies of a given digraph G is said to be an orthogonal decomposition of the complete digraph D/sub n/ by G, if every arc of D/sub n/ belongs to exactly one member of G and the union of any two different elements from G contains precisely one pair of reverse arcs. Given a digraph h, an h family mh is the vertex-disjoint union of m copies of h . In this paper, we consider orthogonal decompositions by h-families. Our objective is to prove the existence of such an orthogonal decomposition whenever certain necessary conditions hold and m is sufficiently large

orthogonal decompositions
complete digraphs
isomorphic copies
vertex-disjoint union
necessary conditions


The quadratic 0-1 knapsack problem with series-parallel support

Abstract: We consider various special cases of the quadratic 0-1 knapsack problem (QKP) for which the underlying graph structure is fairly simple. For the variant with edge series-parallel graphs, we give a dynamic programming algorithm with pseudo-polynomial time complexity, and a fully polynomial time approximation scheme. In strong contrast to this, the variant with vertex series-parallel graphs is shown to be strongly NP-complete


Automated cerebrum segmentation from three-dimensional sagittal brain MR images

Abstract: We present a fully automated cerebrum segmentation algorithm for full three-dimensional sagittal brain MR images. First, cerebrum segmentation from a midsagittal brain MR image is performed utilizing landmarks, anatomical information, and a connectivity-based threshold segmentation algorithm as previously reported. Recognizing that the cerebrum in laterally adjacent slices tends to have similar size and shape, we use the cerebrum segmentation result from the midsagittal brain MR image as a mask to guide cerebrum segmentation in adjacent lateral slices in an iterative fashion. This masking operation yields a masked image (preliminary cerebrum segmentation) for the next lateral slice, which may truncate brain region(s). Truncated regions are restored by first finding end points of their boundaries, by comparing the mask image and masked image boundaries, and then applying a connectivity-based algorithm. The resulting final extracted cerebrum image for this slice is then used as a mask for the next lateral slice. The algorithm yielded satisfactory fully automated cerebrum segmentations in three-dimensional sagittal brain MR images, and had performance superior to conventional edge detection algorithms for segmentation of cerebrum from 3D sagittal brain MR images


Female computer science doctorates: what does the survey of earned doctorates reveal?

Abstract: Based on the National Center for Education Statistics (2000), in the 1997-1998 academic year 26.7% of earned bachelors' degrees, 29.0% of earned masters' degrees and 16.3% of earned doctorates' degrees in computer science were awarded to women. As these percentages suggest, women are underrepresented at all academic levels in computer science (Camp, 1997). The most severe shortage occurs at the top level-the doctorate in computer science. We know very little about the women who persist to the top level of academic achievement in computer science. This paper examines a subset of data collected through the Survey of Earned Doctorates (SED). The specific focus of this paper is to identify trends that have emerged from the SED with respect to females completing doctorates in computer science between the academic years 1990-1991 and 1999-2000. Although computer science doctorates include doctorates in information science, prior research (Camp, 1997) suggests that the percentage of women completing doctorates in information science as compared to computer science is low. The specific research questions are: 1. How does the percentage of women who complete doctorates in computer science compare to those that complete doctorates in other fields? 2. How does the length of time in school and the sources of funding differ for females as compared to males who complete doctorates in computer science? 3. Where do women go after completing doctorates in computer science and what positions do they acquire? How do these experiences differ from their male peers?

female computer science doctorates
Survey of Earned Doctorates
information science


The mutual effects of grid and wind turbine voltage stability control

Abstract: This note considers the results of wind turbine modelling and power system stability investigations. Voltage stability of the power grid with grid-connected wind turbines will be improved by using blade angle control for a temporary reduction of the wind turbine power during and shortly after a short circuit fault in the grid

grid voltage stability control
wind turbine voltage stability control
wind turbine modelling
power system stability
power grid
grid-connected wind turbines
blade angle control
wind turbine power reduction
short circuit fault
offshore wind turbines


The disconnect continues [digital content providers]

Abstract: The relationships between the people who buy digital content and those who sell it are probably more acrimonious than ever before, says Dick Curtis, a director and lead analyst for the research firm Outsell Inc., where he covers econtent contract and negotiation strategies. Several buyers agree with his observation. They cite aggressive sales tactics, an unwillingness to deliver content in formats buyers need, a reluctance to provide licensing terms that take into account the structure of today's corporations, and inadequate service and support as a few of the factors underlying the acrimony. Still, many buyers remain optimistic that compromises can be reached on some of these issues. But first, they say, sellers must truly understand the econtent needs of today's enterprises

digital content
econtent contract
econtent negotiation
sales tactics
econtent buyers
news databases
Web site


Stability of W-methods with applications to operator splitting and to geometric theory

Abstract: We analyze the stability properties of W-methods applied to the parabolic initial value problem u' + Au = Bu. We work in an abstract Banach space setting, assuming that A is the generator of an analytic semigroup and that B is relatively bounded with respect to A. Since W-methods treat the term with A implicitly, whereas the term involving B is discretized in an explicit way, they can be regarded as splitting methods. As an application of our stability results, convergence for nonsmooth initial data is shown. Moreover, the layout of a geometric theory for discretizations of semilinear parabolic problems u' + Au = f (u) is presented

W-methods stability
operator splitting
geometric theory
parabolic initial value problem
abstract Banach space
analytic semigroup
nonsmooth initial data
linearly implicit Runge-Kutta methods


Networking in the palm of your hand [PDA buyer's guide]

Abstract: As PDAs move beyond the personal space and into the enterprise, you need to get a firm grip on the options available for your users. What operating system do you choose? What features do you and your company need? How will these devices fit into the existing corporate infrastructure? What about developer support?

PDAs
operating system
corporate infrastructure
developer support
buyer's guide


The chromatic spectrum of mixed hypergraphs

Abstract: A mixed hypergraph is a triple H = (X, C, D), where X is the vertex set, and each of C, D is a list of subsets of X. A strict k-coloring of H is a surjection c : X {1,..., k} such that each member of le has two vertices assigned a common value and each member of D has two vertices assigned distinct values. The feasible set of H is {k: H has a strict k-coloring}. Among other results, we prove that a finite set of positive integers is the feasible set of some mixed hypergraph if and only if it omits the number I or is an interval starting with 1. For the set {s, t} with 2 <or= s <or= t - 2, the smallest realization has 2t - s vertices. When every member of C union D is a single interval in an underlying linear order on the vertices, the feasible set is also a single interval of integers

chromatic spectrum
mixed hypergraphs
vertex set
strict k-coloring
positive integers
mixed hypergraph


Questioning the RFP process [telecom]

Abstract: In the current climate, the most serious concern about the purchasing habits of telecom carriers is obviously the lack of spending. Even against a backdrop of economic constraints and financial struggles, however, genuine concerns about the purchasing process itself are being raised by some of those closest to it

telecom carriers
purchasing process
sales cycle
request for information
request for proposal


Data assimilation of local model error forecasts in a deterministic model

Abstract: One of the most popular data assimilation techniques in use today are of the Kalman filter type, which provide an improved estimate of the state of a system up to the current time level, based on actual measurements. From a forecasting viewpoint, this corresponds to an updating of the initial conditions. The standard forecasting procedure is to then run the model uncorrected into the future, driven by predicted boundary and forcing conditions. The problem with this methodology is that the updated initial conditions quickly 'wash-out', thus, after a certain forecast horizon the model predictions are no better than from an initially uncorrected model. This study demonstrates that through the assimilation of error forecasts (in the present case made using so-called local models) entire model domains can be corrected for extended forecast horizons (i.e. long after updated initial conditions have become washed-out), thus demonstrating significant improvements over the conventional methodology. Some alternate uses of local models are also explored for the re-distribution of error forecasts over the entire model domain, which are then compared with more conventional Kalman filter type schemes

data assimilation
local model error forecasts
deterministic model
Kalman filter
forcing conditions
forecast horizon
error prediction
hydrodynamic modelling


A feature-preserving volumetric technique to merge surface triangulations

Abstract: Several extensions and improvements to surface merging procedures based on the extraction of isosurfaces from a distance map defined on an adaptive background grid are presented. The main objective is to extend the application of these algorithms to surfaces with sharp edges and comers. In order to deal with objects of different length scales, the initial background grids are created using a Delaunay triangulation method and local voxelizations. A point enrichment technique that introduces points into the background grid along detected surface features such as ridges is used to ensure that these features are preserved in the final merged surface. The surface merging methodology is extended to include other Boolean operations between surface triangulations. The iso-surface extraction algorithms are modified to obtain the correct iso-surface for multi-component objects. The procedures are demonstrated with various examples, ranging from simple geometrical entities to complex engineering applications. The present algorithms allow realistic modelling of a large number of complex engineering geometries using overlapping components defined discretely, i.e. via surface triangulations. This capability is very useful for grid generation starting from data originated in measurements or images

point enrichment technique background grid

P P P P P P P P P M M R M R P P R P P R P P P M U


Design of an adaptive vibration absorber to reduce electrical transformer structural vibration

Abstract: This paper considers the design of a vibration absorber to reduce structural vibration at multiple frequencies, with an enlarged bandwidth control at these target frequencies. While the basic absorber is a passive device a control system has been added to facilitate tuning, effectively giving the combination of a passive and active device, which leads to far greater stability and robustness. Experimental results demonstrating the effectiveness of the absorber are also described

adaptive vibration absorber
electrical transformer
structural vibration
bandwidth control


Control of transient thermal response during sequential open-die forging: a trajectory optimization approach

Abstract: A trajectory optimization approach is applied to the design of a sequence of open-die forging operations in order to control the transient thermal response of a large titanium alloy billet. The amount of time the billet is soaked in furnace prior to each successive forging operation is optimized to minimize the total process time while simultaneously satisfying constraints on the maximum and minimum values of the billet temperature distribution to avoid microstructural defects during forging. The results indicate that a "differential" heating profile is the most effective at meeting these design goals

transient thermal response control
trajectory optimization
open-die forging
titanium alloy billet
temperature distribution
microstructural defects
heating profile


Model theory for hereditarily finite superstructures

Abstract: We study model-theoretic properties of hereditarily finite superstructures over models of not more than countable signatures. A question is answered in the negative inquiring whether theories of hereditarily finite superstructures which have a unique (up to isomorphism) hereditarily finite superstructure can be described via definable functions. Yet theories for such superstructures admit a description in terms of iterated families TF and SF. These are constructed using a definable union taken over countable ordinals in the subsets which are unions of finitely many complete subsets and of finite subsets, respectively. Simultaneously, we describe theories that share a unique (up to isomorphism) countable hereditarily finite superstructure


Data extraction from the Web based on pre-defined schema

Abstract: With the development of the Internet, the World Wide Web has become an invaluable information source for most organizations. However, most documents available from the Web are in HTML form which is originally designed for document formatting with little consideration of its contents. Effectively extracting data from such documents remains a nontrivial task. In this paper, we present a schema-guided approach to extracting data from HTML pages. Under the approach, the user defines a schema specifying what to be extracted and provides sample mappings between the schema and the HTML page. The system will induce the mapping rules and generate a wrapper that takes the HTML page as input and produces the required data in the form of XML conforming to the user-defined schema. A prototype system implementing the approach has been developed. The preliminary experiments indicate that the proposed semi-automatic approach is not only easy to use but also able to produce a wrapper that extracts required data from inputted pages with high accuracy

data extraction
wrapper generation
data integration
Internet
information source
schema
HTML
distributed database
queries


Sensorless control of induction motor drives

Abstract: Controlled induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor the information on the rotor speed is extracted from measured stator voltages and currents at the motor terminals. Vector-controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open-loop estimators or closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. Dynamic performance and steady-state speed accuracy in the low-speed range can be achieved by exploiting parasitic effects of the machine. The overview in this paper uses signal flow graphs of complex space vector quantities to provide an insightful description of the systems used in sensorless control of induction motors

sensorless control
induction motor drives
reliability
stator voltages
stator currents
vector-controlled drives
magnitude
spatial orientation
fundamental magnetic flux waves
open-loop estimators
closed-loop observers
robustness
sensitivity
model parameter variations
steady-state speed accuracy
parasitic effects
signal flow graphs
space vector quantities


Detection and estimation of abrupt changes in the variability of a process

Abstract: Detection of change-points in normal means is a well-studied problem. The parallel problem of detecting changes in variance has had less attention. The form of the generalized likelihood ratio test statistic has long been known, but its null distribution resisted exact analysis. In this paper, we formulate the change-point problem for a sequence of chi-square random variables. We describe a procedure that is exact for the distribution of the likelihood ratio statistic for all even degrees of freedom, and gives upper and lower bounds for odd (and also for non-integer) degrees of freedom. Both the liberal and conservative bounds for chi /sub 1//sup 2/ degrees of freedom are shown through simulation to be reasonably tight. The important problem of testing for change in the normal variance of individual observations corresponds to the chi /sub 1//sup 2/ case. The non-null case is also covered, and confidence intervals for the true change point are derived. The methodology is illustrated with an application to quality control in a deep level gold mine. Other applications include ambulatory monitoring of medical data and econometrics

R R R P P P P P R P R M R P P P M P P P P P P


A dataflow computer which accelerates execution of sequential programs by precedent firing instructions

Abstract: In the dataflow machine, it is important to avoid degradation of performance in sequential processing, and it is important from the viewpoint of hardware scale to reduce the number of waiting operands. This paper demonstrates that processing performance is degraded by sequential processing in the switching process, and presents a method of remedy. Precedent firing control is proposed as a means of remedy, and it is shown by a simulation that the execution time and the total number of waiting operands can be reduced by the precedent firing control. Then the hardware scale is examined as an evaluation of precedent firing control

dataflow computer
execution acceleration
sequential programs
precedent firing instructions
precedent firing control
execution time
waiting operands
hardware scale
parallel processing
computer architecture
processing performance
switching process


BT voices its support for IP

Abstract: BTexact's chief technology officer, Mick Reeve, gives his views on the future for voice over DSL services and virtual private networks, and defends the slow rollout of public access WLANs

BTexact
voice over DSL
virtual private networks
public access WLANs