1,721,030 research outputs found
Multicriteria fuzzy control using evolutionary programming
No full textIn this paper, we propose a multicriteria fuzzy control (MFC) using evolutionary programming (EP) by which its lambda-fuzzy measure is optimized. Basically the MFC is an extended version of the existing fuzzy logic controller to obtain the proper weights of the fuzzy rules for the fine tuning control. The MFC is designed by three steps: first, the attributes of the system output response are selected, second, the partial evaluations from the viewpoints of the attributes are assigned to the fuzzy rules, and third, the fuzzy integral is employed to aggregate the partial evaluation and the user's fuzzy measure about the consideration degree of each attribute for the proper weight value. EP is used to optimize the lambda-fuzzy measure for the linear tuning property of the MFC. Computer simulations indicate that the proposed scheme has excellent performance. (C) Elsevier Science Inc. 1997
Reducing tilt errors in moire linear encoders using phase-modulated grating
No full textA new hardware compensation method reducing displacement measurement errors, caused by tilt of the index scale in a moire linear encoder, has been developed. In conventional moire linear encoders, the detectors are aligned perpendicular to the line of the moire fringes and this structure is very sensitive to an unwanted tilt of the gratings. In this article, a newly designed grating, called a phase-modulated grating, is developed to compensate for nonorthogonal errors. By using the phase-modulated grating instead of a conventional index, it is possible to reduce nonorthogonal errors of the moire linear encoder. (C) 2000 American Institute of Physics. [S0034-6748(00)04506-8]
DNA methylation, an epigenetic mechanism connecting folate to healthy embryonic development and aging.
No full textExperimental studies demonstrated that maternal exposure to certain environmental and dietary factors during early embryonic development can influence the phenotype of offspring as well as the risk of disease development at the later life. DNA methylation, an epigenetic phenomenon, has been suggested as a mechanism by which maternal nutrients affect the phenotype of their offspring in both honeybee and agouti mouse models. Phenotypic changes through DNA methylation can be linked to folate metabolism by the knowledge that folate, a coenzyme of one-carbon metabolism, is directly involved in methyl group transfer for DNA methylation. During the fetal period, organ-specific DNA methylation patterns are established through epigenetic reprogramming. However, established DNA methylation patterns are not immutable and can be modified during our lifetime by the environment. Aberrant changes in DNA methylation with diet may lead to the development of age-associated diseases including cancer. It is also known that the aging process by itself is accompanied by alterations in DNA methylation. Diminished activity of DNA methyltransferases (Dnmts) can be a potential mechanism for the decreased genomic DNA methylation during aging, along with reduced folate intake and altered folate metabolism. Progressive hypermethylation in promoter regions of certain genes is observed throughout aging, and repression of tumor suppressors induced by this epigenetic mechanism appears to be associated with cancer development. In this review, we address the effect of folate on early development and aging through an epigenetic mechanism, DNA methylation
An averaging method for optical triangulation displacement sensors using diffraction grating
No full textOptical triangulation displacement sensors are widely used in many applications due to the advantages of noncontact measurement, simple structure, good resolution, and long operating range. However, they commonly have several errors, such as speckle effects and electronic noises, etc. Among them, reducing electronic noises is very tedious and hard. To reduce the effect of electronic noises, conventional systems use sequential averaging techniques. Since electronic noises are random in nature, their variances can be reduced with an averaging operation. However, the averaging is inherently a time-consuming process which requires many measurements. To reduce the time for averaging and the number of measurements, several sensor modules or faster signal processing hardware are required. Therefore, these alternatives are not cost effective and increase the size of the measurement system. In this article, we propose a simple and cost-effective system structure for optical triangulation displacement sensors, which reduces time for averaging and the number of measurements by using a transmission-type diffraction grating. The diffraction grating helps us to obtain several signals simultaneously. Therefore, it is achievable to reduce time for averaging and the number of measurements. The feasibility of the proposed system was verified through experiments. When only two diffracted orders are used for obtaining signals, the rms of noise is reduced by 1/root2. (C) 2001 American Institute of Physics.This work was supported in part by the Brain Korea 21 Project
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