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51.
D. Bjørner 《Cybernetics and Systems Analysis》2010,46(4):609-623
In this paper, we wish to advocate that departments of computer science put emphasis on teaching programming and software
engineering based on formal methods; and more emphasis on research into formal methods for the trustworthy development of
software. We also wish to advocate that the concepts of domain science and domain engineering become an indispensable part
of the science of informatics and of software engineering. 相似文献
52.
J. Bjelland M. Burgess G. Canright K. Engø-Monsen 《Data mining and knowledge discovery》2010,20(1):98-151
We study the properties of the principal eigenvector for the adjacency matrix (and related matrices) for a general directed
graph. In particular—motivated by the use of the eigenvector for estimating the “importance” of the nodes in the graph—we
focus on the distribution of positive weight in this eigenvector, and give a coherent picture which builds upon and unites
earlier results. We also propose a simple method—“T-Rank”—for generating importance scores. T-Rank generates authority scores
via a one-level, non-normalized matrix, and is thus distinct from known methods such as PageRank (normalized), HITS (two-level),
and SALSA (two-level and normalized). We show, using our understanding of the principal eigenvector, that T-Rank has a much
less severe “sink problem” than does PageRank. Also, we offer numerical results which quantify the “tightly-knit community”
or TKC effect. We find that T-Rank has a stronger TKC effect than PageRank, and we offer a novel interpolation method which
allows for continuous tuning of the strength of this TKC effect. Finally, we propose two new “sink remedies”, i.e., methods
for ensuring that the principal eigenvector is positive everywhere. One of our sink remedies (source pumping) is unique among
sink remedies, in that it gives a positive eigenvector without rendering the graph strongly connected. We offer a preliminary
evaluation of the effects and possible applications of these new sink remedies. 相似文献
53.
Michael A. Bender Gerth Stølting Brodal Rolf Fagerberg Riko Jacob Elias Vicari 《Theory of Computing Systems》2010,47(4):934-962
We study the problem of sparse-matrix dense-vector multiplication (SpMV) in external memory. The task of SpMV is to compute
y:=Ax, where A is a sparse N×N matrix and x is a vector. We express sparsity by a parameter k, and for each choice of k consider the class of matrices where the number of nonzero entries is kN, i.e., where the average number of nonzero entries per column is k. 相似文献
54.
We present a probabilistic interpretation of inverse kinematics and extend it to sequential data. The resulting model is used
to estimate articulated human motion in visual data. The approach allows us to express the prior temporal models in spatial
limb coordinates, which is in contrast to most recent work where prior models are derived in terms of joint angles. This approach
has several advantages. First of all, it allows us to construct motion models in low dimensional spaces, which makes motion
estimation more robust. Secondly, as many types of motion are easily expressed in spatial coordinates, the approach allows
us to construct high quality application specific motion models with little effort. Thirdly, the state space is a real vector
space, which allows us to use off-the-shelf stochastic processes as motion models, which is rarely possible when working with joint angles. Fourthly, we avoid the problem
of accumulated variance, where noise in one joint affects all joints further down the kinematic chains. All this combined
allows us to more easily construct high quality motion models. In the evaluation, we show that an activity independent version
of our model is superior to the corresponding state-of-the-art model. We also give examples of activity dependent models that
would be hard to phrase directly in terms of joint angles. 相似文献
55.
56.
Christos Doulkeridis Akrivi Vlachou Kjetil Nørvåg Yannis Kotidis Michalis Vazirgiannis 《Peer-to-Peer Networking and Applications》2010,3(1):67-79
The advent of the World Wide Web has made an enormous amount of information available to everyone and the widespread use of
digital equipment enables end-users (peers) to produce their own digital content. This vast amount of information requires scalable data management systems. Peer-to-peer
(P2P) systems have so far been well established in several application areas, with file-sharing being the most prominent.
The next challenge that needs to be addressed is (more complex) data sharing, management and query processing, thus facilitating
the delivery of a wide spectrum of novel data-centric applications to the end-user, while providing high Quality-of-Service.
In this paper, we propose a self-organizing P2P system that is capable to identify peers with similar content and intentionally
assign them to the same super-peer. During content retrieval, fewer super-peers need to be contacted and therefore efficient
similarity search is supported, in terms of reduced network traffic and contacted peers. Our approach increases the responsiveness
and reliability of a P2P system and we demonstrate the advantages of our approach using large-scale simulations. 相似文献
57.
The aims were to evaluate the inter-method reliability of a registration sheet for patient handling tasks, to study the day-to-day variation of musculoskeletal complaints (MSC) and to examine whether patient handling tasks and psychosocial factors were associated with MSC.Nurses (n = 148) fulfilled logbooks for three consecutive working days followed by a day off. Low back pain (LBP), neck/shoulder pain (NSP), knee pain (KP), psychosocial factors (time pressure, stress, conscience of the quality of work) and patient transfers and care tasks were reported.The logbook was reliable for both transfer and care tasks. The numbers of nurses reporting MSC and the level of pain increased significantly during the three working days (15%-30% and 17%-37%, respectively) and decreased on the day off. Stress and transfer task were associated with LPB and transfer tasks were associated with KP.Our results confirm a relationship between work factors and MSC and indicate that logs could be one way to obtain a better understanding of the complex interaction of various nursing working conditions in relation to MSC. 相似文献
58.
Design and validation of structures against blast loads are important for modern society in order to protect and secure its citizen. Since it is a challenge to validate and optimise protective structures against blast loads using full-scale experimental tests, we have to turn our attention towards advanced numerical tools like the finite element method. Several different finite element techniques can be used to describe the response of structures due to blast loads. Some of these are: (1) a pure Lagrangian formulation, (2) an initial Eulerian simulation (to determine the load) followed by a Lagrangian simulation (for the structural response) and (3) a hybrid technique that combines the advantages of Eulerian and Lagrangian methods to have a full coupling between the blast waves and the deformation of the structure. Ideally, all blast simulations should be carried out using the fully coupled Eulerian–Lagrangian approach, but this may not be practical as the computational time increases considerably when going from a pure Lagrangian to a fully coupled Eulerian–Lagrangian simulation. A major goal in this study is to investigate if a pure Lagrangian formulation can be applied to determine the structural response in a specified blast load problem or if more advanced approaches such as the fully coupled Eulerian–Lagrangian approach is required for reliable results. This is done by conducting numerical simulations of an unprotected 20 ft ISO container exposed to a blast load of 4000 kg TNT at 120 m standoff distance using the three different approaches presented above. To validate and discuss the results, the simulated response of the container is compared to available data from a full-scale blast test under such conditions. 相似文献
59.
Jakob Kjøbsted Huusom Niels Kjølstad Poulsen Sten Bay Jørgensen 《Journal of Process Control》2009,19(4):570-578
Iterative Feedback Tuning constitutes an attractive control loop tuning method for processes in the absence of an accurate process model. It is a purely data driven approach aiming at optimizing the closed loop performance. The standard formulation ensures an unbiased estimate of the loop performance cost function gradient with respect to the control parameters. This gradient is important in a search algorithm. The extension presented in this paper further ensures informative data to improve the convergence properties of the method and hence reduce the total number of required plant experiments especially when tuning for disturbance rejection. Informative data is achieved through application of an external probing signal in the tuning algorithm. The probing signal is designed based on a constrained optimization which utilizes an approximate black box model of the process. This model estimate is further used to guarantee nominal stability and to improve the parameter update using a line search algorithm for determining the iteration step size. The proposed algorithm is compared to the classical formulation in a simulation study of a disturbance rejection problem. This type of problem is notoriously difficult for Iterative Feedback Tuning due to the lack of excitation from the reference. 相似文献
60.
Øystein Vedaa Anette Harris Bjørn Bjorvatn Siri Waage Børge Sivertsen Philip Tucker 《Ergonomics》2016,59(1):1-14
A systematic literature search was carried out to investigate the relationship between quick returns (i.e. 11.0 hours or less between two consecutive shifts) and outcome measures of health, sleep, functional ability and work–life balance. A total of 22 studies published in 21 articles were included. Three types of quick returns were differentiated (from evening to morning/day, night to evening, morning/day to night shifts) where sleep duration and sleepiness appeared to be differently affected depending on which shifts the quick returns occurred between. There were some indications of detrimental effects of quick returns on proximate problems (e.g. sleep, sleepiness and fatigue), although the evidence of associations with more chronic outcome measures (physical and mental health and work–life balance) was inconclusive.
Practitioner Summary: Modern societies are dependent on people working shifts. This study systematically reviews literature on the consequences of quick returns (11.0 hours or less between two shifts). Quick returns have detrimental effects on acute health problems. However, the evidence regarding effects on chronic health is inconclusive. 相似文献