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991.
Hee-Byoung Choi Atsushi Konno Masaru Uchiyama 《International Journal of Control, Automation and Systems》2009,7(5):858-864
It is well known that the forward kinematics of parallel robots is a very difficult problem. Closed-form forward kinematics
solutions have been reported only to a few special classes of parallel robots. This paper presents closed-form forward kinematics
solutions of a 4-DOF parallel robot H4. A 16th order polynomial in a single variable is derived to solve the forward kinematics
of the H4. The 16 roots of the polynomial lead to at most 16 different forward kinematics solutions. A numerical verification
is also presented. 相似文献
992.
Classification of semantic relations between nominals 总被引:1,自引:0,他引:1
Roxana Girju Preslav Nakov Vivi Nastase Stan Szpakowicz Peter Turney Deniz Yuret 《Language Resources and Evaluation》2009,43(2):105-121
The NLP community has shown a renewed interest in deeper semantic analyses, among them automatic recognition of semantic relations
in text. We present the development and evaluation of a semantic analysis task: automatic recognition of relations between
pairs of nominals in a sentence. The task was part of SemEval-2007, the fourth edition of the semantic evaluation event previously
known as SensEval. Apart from the observations we have made, the long-lasting effect of this task may be a framework for comparing
approaches to the task. We introduce the problem of recognizing relations between nominals, and in particular the process
of drafting and refining the definitions of the semantic relations. We show how we created the training and test data, list
and briefly describe the 15 participating systems, discuss the results, and conclude with the lessons learned in the course
of this exercise. 相似文献
993.
Jimmy Lin G. Craig Murray Bonnie J. Dorr Jan Hajič Pavel Pecina 《Language Resources and Evaluation》2009,43(1):27-40
Thesauri and controlled vocabularies facilitate access to digital collections by explicitly representing the underlying principles
of organization. Translation of such resources into multiple languages is an important component for providing multilingual
access. However, the specificity of vocabulary terms in most thesauri precludes fully-automatic translation using general-domain
lexical resources. In this paper, we present an efficient process for leveraging human translations to construct domain-specific
lexical resources. This process is illustrated on a thesaurus of 56,000 concepts used to catalog a large archive of oral histories.
We elicited human translations on a small subset of concepts, induced a probabilistic phrase dictionary from these translations,
and used the resulting resource to automatically translate the rest of the thesaurus. Two separate evaluations demonstrate
the acceptability of the automatic translations and the cost-effectiveness of our approach.
相似文献
Jimmy LinEmail: |
994.
Bolette Sandford Pedersen Sanni Nimb Jørg Asmussen Nicolai Hartvig Sørensen Lars Trap-Jensen Henrik Lorentzen 《Language Resources and Evaluation》2009,43(3):269-299
This paper is a contribution to the discussion on compiling computational lexical resources from conventional dictionaries.
It describes the theoretical as well as practical problems that are encountered when reusing a conventional dictionary for
compiling a lexical-semantic resource in terms of a wordnet. More specifically, it describes the methodological issues of
compiling a wordnet for Danish, DanNet, from a monolingual basis, and not—as is often seen—by applying the translational expansion method with Princeton WordNet as the English source.
Thus, we apply as our basis a large, corpus-based printed dictionary of modern Danish. Using this approach, we discuss the
issues of readjusting inconsistent and/or underspecified hyponymy hierarchies taken from the conventional dictionary, sense
distinctions as opposed to the synonym sets of wordnets, generating semantic wordnet relations on the basis of sense definitions,
and finally, supplementing missing or implicit information. 相似文献
995.
Wilhelm Dolle 《Datenschutz und Datensicherheit - DuD》2009,33(3):183-188
Zusammenfassung Im Zeitalter der Informationstechnologie und der umfassenden Vernetzung vieler Systeme ben?tigt ein Dieb weder eine Brechstange
noch muss er im Schutze der Dunkelheit vorgehen. Vielmehr kann er über das Internet, oder lokale Netzwerke, kommen und gehen
wann er will, ohne sich der Gefahr einer Entdeckung und Verhaftung auszusetzen. In vielen F?llen ist ein solcher Einbrecher
l?ngst über alle Berge, bevor seine Tat überhaupt bemerkt wird. Trotzdem hinterl?sst er Spuren — deren Aufspürung und Analyse
die Aufgabe des Computer-Forensikers ist. Zur Unterstützung dieser Arbeit existiert eine Vielzahl an Open-Source-Werkzeugen,
die es durchaus mit ihrer kommerziellen Konkurrenz aufnehmen k?nnen. 相似文献
996.
The maximum entropy principle (MEP) is used to generate a natural probability distribution among the many possible that have
the same moment conditions. The MEP can accommodate higher order moment information and therefore facilitate a higher quality
PDF model. The performance of the MEP for PDF estimation is studied by using more than four moments. For the case with four
moments, the results are compared with those by the Pearson system. It is observed that as accommodating higher order moment,
the estimated PDF converges to the original one. A sensitivity analysis formulation of the failure probability based on the
MEP is derived for reliability-based design optimization (RBDO) and the accuracy is compared with that by finite difference
method (FDM). Two RBDO examples including a realistic three-dimensional wing design are solved by using the derived sensitivity
formula and the MEP-based moment method. The results are compared with other methods such as TR-SQP, FAMM + Pearson system,
FFMM + Pearson system in terms of accuracy and efficiency. It is also shown that an improvement in the accuracy by including
more moment terms can increase numerical efficiency of optimization for the three-dimensional wing design. The moment method
equipped with the MEP is found flexible and well adoptable for reliability analysis and design. 相似文献
997.
Solving engineering design and resources optimization via multiobjective evolutionary algorithms (MOEAs) has attracted much
attention in the last few years. In this paper, an efficient multiobjective differential evolution algorithm is presented
for engineering design. Our proposed approach adopts the orthogonal design method with quantization technique to generate
the initial archive and evolutionary population. An archive (or secondary population) is employed to keep the nondominated
solutions found and it is updated by a new relaxed form of Pareto dominance, called Pareto-adaptive ϵ-dominance (paϵ-dominance), at each generation. In addition, in order to guarantee to be the best performance produced, we propose a new
hybrid selection mechanism to allow the archive solutions to take part in the generating process. To handle the constraints,
a new constraint-handling method is employed, which does not need any parameters to be tuned for constraint handling. The
proposed approach is tested on seven benchmark constrained problems to illustrate the capabilities of the algorithm in handling
mathematically complex problems. Furthermore, four well-studied engineering design optimization problems are solved to illustrate
the efficiency and applicability of the algorithm for multiobjective design optimization. Compared with Nondominated Sorting
Genetic Algorithm II, one of the best MOEAs available at present, the results demonstrate that our approach is found to be
statistically competitive. Moreover, the proposed approach is very efficient and is capable of yielding a wide spread of solutions
with good coverage and convergence to true Pareto-optimal fronts. 相似文献
998.
Reliability-based design optimization of problems with correlated input variables using a Gaussian Copula 总被引:4,自引:2,他引:2
The reliability-based design optimization (RBDO) using performance measure approach for problems with correlated input variables
requires a transformation from the correlated input random variables into independent standard normal variables. For the transformation
with correlated input variables, the two most representative transformations, the Rosenblatt and Nataf transformations, are
investigated. The Rosenblatt transformation requires a joint cumulative distribution function (CDF). Thus, the Rosenblatt
transformation can be used only if the joint CDF is given or input variables are independent. In the Nataf transformation,
the joint CDF is approximated using the Gaussian copula, marginal CDFs, and covariance of the input correlated variables.
Using the generated CDF, the correlated input variables are transformed into correlated normal variables and then the correlated
normal variables are transformed into independent standard normal variables through a linear transformation. Thus, the Nataf
transformation can accurately estimates joint normal and some lognormal CDFs of the input variable that cover broad engineering
applications. This paper develops a PMA-based RBDO method for problems with correlated random input variables using the Gaussian
copula. Several numerical examples show that the correlated random input variables significantly affect RBDO results. 相似文献
999.
Atsushi Kawamoto 《Structural and Multidisciplinary Optimization》2009,37(4):429-433
This paper deals with the design of compliant mechanisms in a continuum-based finite-element representation. Because the displacements
of mechanisms are intrinsically large, the geometric nonlinearity is essential for designing such mechanisms. However, the
consideration of the geometric nonlinearity may cause some instability in topology optimization. The problem is in the analysis
part but not in the optimization part. To alleviate the analysis problem and eventually stabilize the optimization process,
this paper proposes to apply the Levenberg–Marquardt method to the nonlinear analysis of compliant mechanisms. 相似文献
1000.
The design of systems for dynamic response may involve constraints that need to be satisfied over an entire time interval
or objective functions evaluated over the interval. Efficiently performing the constrained optimization is challenging, since
the typical response is implicitly linked to the design variables through a numerical integration of the governing differential
equations. Evaluating constraints is costly, as is the determination of sensitivities to variations in the design variables.
In this paper, we investigate the application of a temporal spectral element method to the optimization of transient and time-periodic
responses of fundamental engineering systems. Through the spectral discretization, the response is computed globally, thereby
enabling a more explicit connection between the response and design variables and facilitating the efficient computation of
response sensitivities. Furthermore, the response is captured in a higher order manner to increase analysis accuracy. Two
applications of the coupling of dynamic response optimization with the temporal spectral element method are demonstrated.
The first application, a one-degree-of-freedom, linear, impact absorber, is selected from the auto industry, and tests the
ability of the method to treat transient constraints over a large-time interval. The second application, a related mass-spring-damper
system, shows how the method can be used to obtain work and amplitude optimal time-periodic control force subject to constraints
over a periodic time interval.
This research was performed while the first author held a National Research Council Research Associateship Award at the Air
Force Research Laboratory.
An early version of this paper was presented at the 46th AIAA Aerospace Sciences Meeting and Exhibit, Jan 7–10, 2008, Reno,
Nevada. 相似文献