• The Korean Journal of Applied Statistics
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• v.5 no.1
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• pp.9-17
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• 1992

In this paper we give a Bayesian approach to problems of estimation for the ratio in finite populations. Adopting the Ericson's superpopulatin approach in which the finite population of size N is viewed as arising form a random sample of N units from some superpopulation. We derive the exact posterior of the ratio under the noninformative prior on superpopulation parameters. Based on our results we compute an exact Bayesian confidence interval and compare this with the existing methods.

• The Journal of Korea Robotics Society
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• v.9 no.1
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• pp.20-27
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• 2014

In this paper, an exact reshaping method for the motor dynamics of a flexible-joint robot is proposed using an integral manifold approach. Obtaining the exact model for both motor-side and link-side dynamics of a flexible-joint robot is difficult due to its under-actuated nature and complex dynamics. Despite the simple structure of the motor-side dynamics, they are difficult to model accurately for a flexible-joint robot due to motor disturbances, especially when speed reducers such as harmonic drives are installed. An integral manifold feedback control (IMFC) is proposed to reshape the motor dynamics. Based on the integral manifold approach, it is theoretically proved that the IMFC reshapes motor dynamics exactly even with bounded disturbances such as motor friction. The performance of the proposed IMFC is verified experimentally using a single degree-of-freedom flexible-joint robot under gravity conditions.

• Coupled systems mechanics
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• v.11 no.6
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• pp.525-542
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• 2022

In this work we present an advanced approach to the design of small wind turbine support steel structures. To this end we use an improved version of previously developed geometrically exact beam models. Namely, three different geometrically exact beam models are used, the first two are the Reissner and the Kirchhoff beam models implementing bi-linear hardening response and the third is the Reissner beam capable of also representing connections response. All models were validated in our previous research for a static response, and in this work they are extended to dynamic response. With these advanced models, we can perform analysis of four practical solutions for the installation of small wind turbines in new or existing buildings including effects of elastoplastic response to vibration problems. The numerical simulations confirm the robustness of numerical models in analyzing vibration problems and the crucial effects of elastoplastic response in avoiding resonance phenomena.

• Journal of applied mathematics & informatics
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• v.28 no.5_6
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• pp.1477-1487
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• 2010

In this paper, we give a solving approach based on a logarithmic-exponential multiplier penalty function for the constrained minimization problem. It is proved exact in the sense that the local optimizers of a nonlinear problem are precisely the local optimizers of the logarithmic-exponential multiplier penalty problem.

• International Journal of Highway Engineering
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• v.18 no.2
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• pp.51-60
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• 2016

PURPOSES : The applicability of the mechanics-based similarity concept (suggested by Feng et al.) for determining scaled variables, including length and load, via laboratory-scale tests and discrete element analysis, was evaluated. METHODS: Several studies on the similarity concept were reviewed. The exact scaling approach, a similarity concept described by Feng, was applied in order to determine an analytical solution of a free-falling ball. This solution can be considered one of the simplest conditions for discrete element analysis. RESULTS : The results revealed that 1) the exact scaling approach can be used to determine the scale of variables in laboratory tests and numerical analysis, 2) applying only a scale factor, via the exact scaling approach, is inadequate for the error-free replacement of small particles by large ones during discrete element analysis, 3) the level of continuity of flowable materials such as SCC and cement mortar seems to be an important criterion for evaluating the applicability of the similarity concept, and 4) additional conditions, such as the kinetics of particle, contact model, and geometry, must be taken into consideration to achieve the maximum radius of replacement particles during discrete element analysis. CONCLUSIONS : The concept of similarity is a convenient tool to evaluate the correspondence of scaled laboratory test or numerical analysis to physical condition. However, to achieve excellent correspondence, additional factors, such as the kinetics of particles, contact model, and geometry, must be taken into consideration.

• Structural Engineering and Mechanics
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• v.43 no.3
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• pp.273-285
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• 2012

Structural reanalysis is frequently used to reduce the computational cost during the process of design or optimization. The supports can be regarded as the design variables in various types of structural optimization problems. The location, number, and type of supports may be varied in order to yield a more effective design. The paper is focused on structural static reanalysis problem with added supports where some node displacements along axes of the global coordinate system are specified. A new approach is proposed and exact solutions can be provided by the approach. Thus, it belongs to the direct reanalysis methods. The information from the initial analysis has been fully exploited. Numerical examples show that the exact results can be achieved and the computational time can be significantly reduced by the proposed method.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.6
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• pp.41-50
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• 2012

This paper presents a new sequence alignment method using the divide approach, which solves the problem by decomposing sequence alignment into several sub-alignments with respect to exact matching subsequences. Exact matching subsequences in the proposed method are bounded on the generalized suffix tree of two sequences, such as protein domain length more than 7 and less than 7. Experiment results show that protein sequence pairs chosen in PFAM database can be aligned using this method. In addition, this method reduces the time about 15% and space of the conventional dynamic programming approach. And the sequences were classified with 94% of accuracy.

• Advances in nano research
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• v.17 no.1
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• pp.19-32
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• 2024

Functionally graded-carbon nanotube (FG-CNT) is expected to be a new generation of materials with a wide range of potential applications in technological fields such as aerospace, defense, energy, and structural industries. In this paper, an exact finite strip method for functionally graded-carbon nanotube sandwich plates is developed using first-order shear deformation theory to get the exact natural frequencies of the plates. The face sheets of the plates are made of FG-CNT with continuous and smooth grading based on the power law index. The equations of motion have been generated based on the Hamilton principle. By extracting the exact stiffness matrix for any strip of the sandwich plate as a non-algebraic function of natural frequencies, it is possible to calculate the exact free vibration frequencies. The accuracy and efficiency of the current method is established by comparing its findings to the results of the literature works. Examples are presented to prove the efficiency of the generated method to deal with various problems, such as the influence of the length-to-height ratio, the power law index, and a core-to-face sheet thickness of the single and multi-span sandwich plates with various boundary conditions on the natural frequencies. The exact results obtained from this analysis can check the validity and accuracy of other numerical methods.

• The Pure and Applied Mathematics
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• v.22 no.2
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• pp.179-184
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• 2015

In this paper we discuss a functional approach to obtain a lattice-like structure in d-algebras, and obtain an exact analog of De Morgan law and some other properties.

• ETRI Journal
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• v.15 no.3
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• pp.35-45
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• 1994

In this paper we develop an approximation formalism on the queue length distribution for general queueing models. Our formalism is based on two steps of approximation; the first step is to find a lower bound on the exact formula, and subsequently the Chernoff upper bound technique is applied to this lower bound. We demonstrate that for the M/M/1 model our formula is equivalent to the exact solution. For the D/M/1 queue, we find an extremely tight lower bound below the exact formula. On the other hand, our approach shows a tight upper bound on the exact distribution for both the ND/D/1 and M/D/1 queues. We also consider the $M+{\Sigma}N_jD/D/1$ queue and compare our formula with other formalisms for the $M+{\Sigma}N_jD/D/1$ and M+D/D/1 queues.