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排序方式: 共有100条查询结果,搜索用时 890 毫秒
51.
In this paper, an adaptive observer for robust control of robotic manipulators is proposed.The lumped uncertainty is estimated using Chebyshev polynomials. Usually, the uncertainty upper bound is required in designing observer-controller structures. However, obtaining this bound is a challenging task. To solve this problem, many uncertainty estimation techniques have been proposed in the literature based on neuro-fuzzy systems. As an alternative, in this paper, Chebyshev polynomials have been applied to uncertainty estimation due to their simpler structure and less computational load.Based on strictly-positive-real(SPR) Lyapunov theory, the stability of the closed-loop system can be verified. The Chebyshev coefficients are tuned based on the adaptation rules obtained in the stability analysis. Also, to compensate the truncation error of the Chebyshev polynomials, a continuous robust control term is designed while in previous related works, usually a discontinuous term is used. An SCARA manipulator actuated by permanent magnet DC motors is used for computer simulations.Simulation results reveal the superiority of the designed method. 相似文献
52.
Andreas Houben Ali Mohammad Banaei-Moghaddam Sonja Klemme Jeremy N. Timmis 《Cellular and molecular life sciences : CMLS》2014,71(3):467-478
B chromosomes (Bs) are dispensable components of the genome exhibiting non-Mendelian inheritance and have been widely reported on over several thousand eukaryotes, but still remain an evolutionary mystery ever since their first discovery over a century ago [1]. Recent advances in genome analysis have significantly improved our knowledge on the origin and composition of Bs in the last few years. In contrast to the prevalent view that Bs do not harbor genes, recent analysis revealed that Bs of sequenced species are rich in gene-derived sequences. We summarize the latest findings on supernumerary chromosomes with a special focus on the origin, DNA composition, and the non-Mendelian accumulation mechanism of Bs. 相似文献
53.
Rami I. Aqeilan Muhannad Abu-Remaileh Mohammad Abu-Odeh 《Cellular and molecular life sciences : CMLS》2014,71(23):4589-4599
The fragile WWOX gene, encompassing the chromosomal fragile site FRA16D, is frequently altered in human cancers. While vulnerable to DNA damage itself, recent evidence has shown that the WWOX protein is essential for proper DNA damage response (DDR). Furthermore, the gene product, WWOX, has been associated with multiple protein networks, highlighting its critical functions in normal cell homeostasis. Targeted deletion of Wwox in murine models suggests its in vivo requirement for proper growth, metabolism, and survival. Recent molecular and biochemical analyses of WWOX functions highlighted its role in modulating aerobic glycolysis and genomic stability. Cumulatively, we propose that the gene product of FRA16D, WWOX, is a functionally essential protein that is required for cell homeostasis and that its deletion has important consequences that contribute to the neoplastic process. This review discusses the essential role of WWOX in tumor suppression and genomic stability and how its alteration contributes to cancer transformation. 相似文献
54.
55.
Mohammad Sadegh Shakeri 《矿物冶金与材料学报》2014,21(4):401-407
In the present research, the effect of CeO2 dopant on the fabrication of transparent lithium aluminosilicate titanate (LAST) glass ceramics was investigated. Nanocrystallineβ-quartz solid solution (s.s.) was observed to be the main phase crystallized in this system. Com-parable refractive indices of the glassy matrix andβ-quartz s.s., as well as the incorporation of very fine grains size were determined as the main reasons for retaining the transparency of the glass ceramics. CeO2 was introduced as a suitable optical agent, playing a role as a network modifier in the glass ceramics, because it does not accelerate the growth process and retards the extended growth of crystals. Optical investi-gations indicate that the Fermi energy level, direct and indirect band gaps, and Urbach energy decrease with increasing nanocrystal content in the glassy matrix of specimens, which can be related to the expansion of conduction band, the enhancement of ionic bonds in the crystal lat-tice, and the enhancement of structural arrangement degree, respectively. 相似文献
56.
Kinetic modeling of copper bioleaching from low-grade ore from the Shahrbabak Copper Complex 下载免费PDF全文
Saman Beikzadeh Noei Saeed Sheibani Fereshteh Rashchi Seyed Mohammad Javad Mirazimi 《矿物冶金与材料学报》2017,24(6):611-620
The copper recovery from low-grade copper sulfide ore was investigated using microbial leaching. Several parameters substantially affect the bioleaching of copper; among them, pulp density and nutrient media were selected for investigation. The optimum conditions for copper recovery were a pulp density of 5 g/mL, a mixed-mineral salt medium of Acidithiobacillus thiooxidans (70vol%) and Acidithiobacillus ferrooxidans (30vol%), and 10vol% of inoculum. Under these conditions, the maximum bioleaching capacity of the medium for copper recovery was determined to be approximately 99%. The effect of pulp density on the kinetics of the bioleaching process was surveyed using both da Silva's method and constrained multilinear regression analysis. The kinetics of copper dissolution followed the shrinking core model, and the process was diffusion controlled at a pulp density of 5 g/mL. Nevertheless, at higher pulp densities, the process was controlled by chemical reaction. 相似文献
57.
Poulikakos PI Persaud Y Janakiraman M Kong X Ng C Moriceau G Shi H Atefi M Titz B Gabay MT Salton M Dahlman KB Tadi M Wargo JA Flaherty KT Kelley MC Misteli T Chapman PB Sosman JA Graeber TG Ribas A Lo RS Rosen N Solit DB 《Nature》2011,480(7377):387-390
Activated RAS promotes dimerization of members of the RAF kinase family. ATP-competitive RAF inhibitors activate ERK signalling by transactivating RAF dimers. In melanomas with mutant BRAF(V600E), levels of RAS activation are low and these drugs bind to BRAF(V600E) monomers and inhibit their activity. This tumour-specific inhibition of ERK signalling results in a broad therapeutic index and RAF inhibitors have remarkable clinical activity in patients with melanomas that harbour mutant BRAF(V600E). However, resistance invariably develops. Here, we identify a new resistance mechanism. We find that a subset of cells resistant to vemurafenib (PLX4032, RG7204) express a 61-kDa variant form of BRAF(V600E), p61BRAF(V600E), which lacks exons 4-8, a region that encompasses the RAS-binding domain. p61BRAF(V600E) shows enhanced dimerization in cells with low levels of RAS activation, as compared to full-length BRAF(V600E). In cells in which p61BRAF(V600E) is expressed endogenously or ectopically, ERK signalling is resistant to the RAF inhibitor. Moreover, a mutation that abolishes the dimerization of p61BRAF(V600E) restores its sensitivity to vemurafenib. Finally, we identified BRAF(V600E) splicing variants lacking the RAS-binding domain in the tumours of six of nineteen patients with acquired resistance to vemurafenib. These data support the model that inhibition of ERK signalling by RAF inhibitors is dependent on levels of RAS-GTP too low to support RAF dimerization and identify a novel mechanism of acquired resistance in patients: expression of splicing isoforms of BRAF(V600E) that dimerize in a RAS-independent manner. 相似文献
58.
59.
1IntroductionTiledesigllalldof)erati()lloftilt.egratedmultiplewatersuppliesandhydroelectricfacilitiestol>ostutilizea1'egi()llalt-c'aterresourcecallcollstituteacolllplexanddifficultoptimizationprohleln.involvingill('tilt(-'r;\('tiollofI)oliti('alalldlegalprocesses,institutiollalregulat,ionsalldengilleerillgecollolllics.Tllolastqllart('rofa(}elltur}'11aswitllessedasigllificantdevelopmelltofoptimizatiollalgol'itllllls.Tillsif('ti\.it}'ilasI>een1llotivatedbytwomajorfactorsftherapidevolutiollofcom… 相似文献
60.
TONG Hau-Lee Mohammad Faizal Ahmad Fauzi Ryoichi Komiya HAW Su-Cheng 《东华大学学报(英文版)》2010,27(2):246-249
In order to develop an automated segmentation system for Computed Tomography (CT) brain images, a new approach which consists of several unsupervised segmentation techniques was introduced. The system segments the CT brain images into three partitions, i. e., abnormalities, cerebrospinal fluid (CSF), and brain matter. Our approach consists of two phase-segmentation methods. In the first phase segmentation, k-means and fuzzy c-means (FCM) methods were implemented to segment and transform the images into the binary images. Based on the connected component in binary images, a decision tree was employed for the annotation of normal or abnormal regions, In the second phase segmentation, the modified FCM with population-diameter independent (PDI) segmentation was applied to segment the images into CSF and brain matter. The experimental results have shown that our proposed system is feasible and yield satisfactory results. 相似文献