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排序方式: 共有142条查询结果,搜索用时 15 毫秒
61.
62.
A comparison of bloat control methods for genetic programming 总被引:2,自引:0,他引:2
Genetic programming has highlighted the problem of bloat, the uncontrolled growth of the average size of an individual in the population. The most common approach to dealing with bloat in tree-based genetic programming individuals is to limit their maximal allowed depth. An alternative to depth limiting is to punish individuals in some way based on excess size, and our experiments have shown that the combination of depth limiting with such a punitive method is generally more effective than either alone. Which such combinations are most effective at reducing bloat? In this article we augment depth limiting with nine bloat control methods and compare them with one another. These methods are chosen from past literature and from techniques of our own devising. esting with four genetic programming problems, we identify where each bloat control method performs well on a per-problem basis, and under what settings various methods are effective independent of problem. We report on the results of these tests, and discover an unexpected winner in the cross-platform category. 相似文献
63.
Arrays of Au nanowells (NWs) were fabricated by electron-beam lithography (EBL) and characterized by surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS). It is revealed that these Au NW arrays exhibit multiple SP resonances that can be tuned by adjusting the geometrical characteristics of the NWs. SERS activity of Au NWs was confirmed for a range of excitation wavelengths and a number of model compounds including rhodamine 6G (R6G), phthalazine, and single-stranded oligonucleotides. According to numerical simulations based on the discrete dipole approximation (DDA), SERS enhancement originates from high electromagnetic fields (hot spots) localized both inside and outside individual NWs. In addition, far-field intercoupling effects between NWs have been observed experimentally in arrays with subwavelength pitch sizes. We show that the SERS enhancement factors can also be tuned and optimized by adjusting the geometry of NWs. 相似文献
64.
Tanasescu S Maxim F Teodorescu F Giurgiu L 《Journal of nanoscience and nanotechnology》2008,8(2):914-923
The thermodynamic behavior and spin dynamics of the colossal magnetoresistive (CMR) perovskites of general formula La(1-x)(A)xMn(1-y)(B)yO3 (where A is an alkaline earth, and B = Al, In) have been studied in order to evidence the effect of composition and the influence of nanocrystallinity on the thermodynamic and magnetic characteristics. By using electron paramagnetic resonance (EPR) spectroscopy, the behavior of the exchange coupling integral (J) between Mn spins and the polaron activation energy (Ea) have been investigated. The thermodynamic properties represented by the relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressures of oxygen have been obtained by using solid electrolyte electrochemical cells method. The influence of the oxygen stoichiometry change on the thermodynamic properties was examined using the data obtained by a coulometric titration technique coupled with measurements of the electromotive force (EMF). The results were correlated with the average Mn valence values as determined by redox titration. The properties of the rare-earth manganites are strongly affected by the A- and B-site substitution and by the oxygen nonstoichiometry. New features related to the modifications in properties connected with the nanocrystalline state were evidenced. The correlation existing between the magnetic and thermodynamic characteristics were discussed in relation to significant changes in the overall concentration of defects. 相似文献
65.
Edward Furimsky J.Anthony MacPhee Liviu Vancea Lynn A. Ciavaglia Biswanath N. Nandi 《Fuel》1983,62(4):395-400
Two bituminous coals, a high volatile Eastern Canadian and a medium volatile Western Canadian, were used to investigate the effect of oxidation on yields and chemical composition of gases, liquids and chars produced during coal pyrolysis. Pyrolysis experiments were performed at 500 °C using the Fischer assay method. Mild oxidation of coals resulted in a decrease of liquid hydrocarbon yields. Further coal oxidation increased the proportion of aromatic carbon in liquid products as determined by n.m.r., and also increased the content of oxygen in liquid products. The content of oxygen in chars was markedly lower than in corresponding coals. An attempt is made to explain reactions occurring during oxidation and subsequent pyrolysis of coal on the basis of differences in chemical composition of gases, liquids and chars. 相似文献
66.
Maria Ignat Petrisor Samoila Corneliu Cojocaru Liviu Sacarescu Valeria Harabagiu 《Chemical Engineering Communications》2016,203(12):1591-1599
Magnetic chitosan–zinc ferrite (ChZnF) composites were proposed as potential adsorbents due to their appropriate physical characteristics and facile separation under external magnetic fields. The magnetic component (ZnFe2O4) was prepared by the sol–gel autocombustion method that yields nanometric spinel compounds with narrow size distribution and with low energy consumption. A certain amount of magnetic powder was dispersed consecutively by ultrasonication in a chitosan-PEG (polyethylene glycol) mixture, in order to obtain the desired nanocomposite. The as-obtained materials were characterized by FT-IR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), TEM (transmission electron microscopy), small-angle X-ray scattering, and Brunauer–Emmett–Teller test measurements. Finally, the chitosan-ferrite nanomaterial was successfully tested in simulated wastewater treatments. Different kinetic and equilibrium models have been fitted by nonlinear regression to analyze the adsorption data. 相似文献
67.
Robert Gorkin Salar Soroori William Southard Liviu Clime Teodor Veres Horacio Kido Lawrence Kulinsky Marc Madou 《Microfluidics and nanofluidics》2012,12(1-4):345-354
In traditional centrifugal microfluidic platforms pumping is restricted to outward fluid flow, resulting in potential real estate issues for embedding complex microsystems. To overcome the limitation, researchers utilize hydrophilic channels to force liquids short distances back toward the disk center. However, most polymers used for CD fabrication are natively hydrophobic, and creating hydrophilic conditions requires surface treatments/specialized materials that pose unique challenges to manufacturing and use. This work describes a novel technology that enjoys the advantages of hydrophilic fluidics on a hydrophobic disk device constructed from untreated polycarbonate plastic. The method, termed suction-enhanced siphoning, is based on exploiting the non-linear hydrostatic pressure profile and related pressure drop created along the length of a rotating microchannel. Theoretical analysis as well as experimental validation of the system is provided. In addition, we demonstrate the use of the hydrostatic pressure pump as a new method for priming hydrophobic-based siphon structures. The development of such techniques for hydrophobic fluidics advances the capabilities of the centrifugal microfluidic platform while remaining true to the goal of creating disposable polymer devices using feasible manufacturing schemes. 相似文献
68.
Liviu S. Enache Elena L. Enache Christophe Ramière Olivier Diaz Ligia Bancu Anca Sin Patrice André 《International journal of molecular sciences》2014,15(10):17644-17666
Liver disease is a major cause of morbidity and mortality worldwide. As in other fields of medicine, there is a stringent need for non-invasive markers to improve patient diagnostics, monitoring and prognostic ability in liver pathology. Cell-free circulating RNA molecules have been recently acknowledged as an important source of potential medical biomarkers. However, many aspects related to the biology of these molecules remain to be elucidated. In this review, we summarize current concepts related to the origin, transportation and possible functions of cell-free RNA. We outline current development of extracellular RNA-based biomarkers in the main forms of non-inherited liver disease: chronic viral hepatitis, hepatocellular carcinoma, non-alcoholic fatty liver, hepato-toxicity, and liver transplantation. Despite recent technological advances, the lack of standardization in the assessment of these markers makes their adoption into clinical practice difficult. We thus finally review the main factors influencing quantification of circulating RNA. These factors should be considered in the reporting and interpretation of current findings, as well as in the proper planning of future studies, to improve reliability and reproducibility of results. 相似文献
69.
The aim of this study is to investigate the migration of heavy metals in meat can under different parameters (varnish, storage time, storage temperature, storage humidity and varnish width and porosity). The physicochemical and organoleptic properties of the meat can have been analyzed. The metal content (Cd, Pb, Cu, Fe, Zn and Sn) were determined by flame and graphite furnace atomic absorption spectrometry after microwave digestion. The organoleptic and physicochemical properties of the samples have not modified significantly during the experiments. The metals migration is not influenced significantly by the varnish type. The highest level of metals in food products was observed at 4 and 50 °C. The porosity influenced significantly (p < 0.05) the migration of metals while the varnish width influence is not a significant one. The migration modeling using 3rd grade polynomial model achieved models with high coefficients of regression (greater than 0.9858). 相似文献
70.
Elena L. Enache Anca Sin Ligia Bancu Christophe Ramière Olivier Diaz Patrice André Liviu S. Enache 《International journal of molecular sciences》2015,16(9):22223-22242
Chronic hepatitis C (CHC) is a major burden for public health worldwide. Although newer direct-acting antivirals show good efficacy, their cost precludes their wide adoption in resource-limited regions. Thus, strategies are being developed to help identify patients with high susceptibility to response to classic PEG-interferon + ribavirin therapy. IL28B polymorphism rs12979860 C/T is an important predictor for an efficient response to interferon-based therapy. A genetic variant in adiponutrin (PNPLA3) gene, rs738409 C/G, is associated with steatosis, severity, and progression of liver fibrosis in CHC patients, and predicts treatment outcome in difficult-to-cure HCV-infected patients with advanced fibrosis. We developed a rapid and inexpensive assay based on duplex high-resolution melting (HRM) for the simultaneous genotyping of these two polymorphisms. The assay validation was performed on synthetic DNA templates and 132 clinical samples from CHC patients. When compared with allele-specific PCR and sequencing, our assay showed 100% (95% CI: 0.9724–1) accuracy, with 100% sensitivity and specificity. Our assay was robust against concentration and quality of DNA samples, melting curve normalization intervals, HRM analysis algorithm, and sequence variations near the targeted SNPs (single nucleotide polymorphism). This duplex assay should provide useful information for patient-oriented management and clinical decision-making in CHC. 相似文献