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61.
The parameterized feedback vertex (arc) set problem is to find whether there are k vertices (arcs) in a given graph whose removal makes the graph acyclic. The parameterized complexity of this problem in general directed graphs is a long standing open problem. We investigate the problems on tournaments, a well studied class of directed graphs. We consider both weighted and unweighted versions. 相似文献
62.
Vishnu Awasthi Sushil K. Pandey Saurabh K. Pandey Shruti Verma Mukul Gupta Shaibal Mukherjee 《Journal of Materials Science: Materials in Electronics》2014,25(7):3069-3076
The growth of CIGS thin films on soda-lime glass substrates at different substrate temperatures by dual ion beam sputtering system in a single-step route from a single quaternary sputtering target with the composition of Cu (In0.70 Ga0.30) Se2 was reported. The effects of the substrate temperature on structural, optical, morphological and electrical properties of CIGS films were investigated. Stoichiometry of one such film was investigated by X-ray photoelectron spectroscopy. All CIGS films had demonstrated a strong (112) orientation located at 2θ ~26.70o, which indicated the chalcopyrite structure of films. The value of full-width at half-maximum of (112) peak was reduced from 0.58° to 0.19° and crystallite size was enlarged from 14.98 to 43.05 nm as growth temperature was increased from 100 to 400 °C. However, atomic force microscope results showed a smooth and uniform surface at lower growth temperature and the surface roughness was observed to increase with increasing growth temperature. Hall measurements exhibited the minimum film resistivity of 0.09 Ω cm with a hole concentration of 2.42 × 1018 cm?3 and mobility of 28.60 cm2 V?1 s?1 for CIGS film grown at 100 °C. Film absorption coefficient was found to enhance nominally from 1 × 105 to 2.3 × 105 cm?1 with increasing growth temperature from 100 to 400 °C. 相似文献
63.
Martensitic Phase Transformation and Deformation Behavior of Fe–Mn–C–Al Twinning‐Induced Plasticity Steel during High‐Pressure Torsion 下载免费PDF全文
64.
Saurabh Das Nicholas Cadirov Sathya Chary Yair Kaufman Jack Hogan Kimberly L. Turner Jacob N. Israelachvili 《Journal of the Royal Society Interface》2015,12(104)
The discovery and understanding of gecko ‘frictional-adhesion’ adhering and climbing mechanism has allowed researchers to mimic and create gecko-inspired adhesives. A few experimental and theoretical approaches have been taken to understand the effect of surface roughness on synthetic adhesive performance, and the implications of stick–slip friction during shearing. This work extends previous studies by using a modified surface forces apparatus to quantitatively measure and model frictional forces between arrays of polydimethylsiloxane gecko footpad-mimetic tilted microflaps against smooth and rough glass surfaces. Constant attachments and detachments occur between the surfaces during shearing, as described by an avalanche model. These detachments ultimately result in failure of the adhesion interface and have been characterized in this study. Stick–slip friction disappears with increasing velocity when the flaps are sheared against a smooth silica surface; however, stick–slip was always present at all velocities and loads tested when shearing the flaps against rough glass surfaces. These results demonstrate the significance of pre-load, shearing velocity, shearing distances, commensurability and shearing direction of gecko-mimetic adhesives and provide us a simple model for analysing and/or designing such systems. 相似文献
65.
Jugal Kishor I. C. Goyal R. L. Sawhney S. P. Singh M. S. Sodha M. Dayal 《国际能源研究杂志》1988,12(4):711-737
This paper presents a thermal model of a fixed dome biogas plant, with or without hot charging and having the ground surface above the plant, blackened and glazed. The rate of energy transfer, between the ground and the plant has been determined by electrical simulation experiments, using a small scale model of the plant (made of copper), suspended in copper sulphate solution. For hot charging a shallow solar pond, built on the ground has been considered. The monthly variation of the slurry temperature, corresponding to 1, 4, 8, 15 and 30 m3 plants have been evaluated for Madras, New Delhi and Srinagar, which correspond to typical hot, composite and cold climates; the following cases have been considered:
- 1 Bare plant, without hot charging and blackening/glazing of the ground, above the plant.
- 2 Plant, charged with hot slurry from a shallow solar pond.
- 3 Plant, with ground above blackened and glazed.
- 4 Plant, with ground above blackened and double glazed and also provision for heating the slurry by burning a part of the produced biogas.
66.
Enteric copolymers of acrylic acid and methyl methacrylate (2.5:7.5 and 2:8) were prepared using tetrahydrofuran as solvent
and AIBN as free radical initiator for colon targeting. FTIR and 1H NMR spectra of the copolymers showed absence of vinyl bond/protons present in the monomers suggesting successful polymerization.
Flurbiprofen sodium microspheres (M1 and M2) made with the copolymers, by oil/oil solvent evaporation, were spherical, anionic
(zeta potential –57.8 and –53.7 mV) and contained 5.47 and 5.89% drug. FTIR spectrum of microspheres showed peaks for aromatic
C = C stretching and substituted benzene ring, indicating entrapment of flurbiprofen. PXRD revealed crystalline structure
of flurbiprofen while copolymer and microspheres were amorphous. DSC thermograms showed a sharp melting endotherm of flurbiprofen
sodium at 129.26°C against broad endotherms of copolymers and microspheres. The microspheres released 43 and 36% drug at pH
6.8 in 2 h and 99 and 96% at pH 7.4 in next 3–4 h.The microspheres did not adhere on gastric-mucosa at pH 1.2 but showed mucoadhesion
time of 18 min and 9 min on intestinal mucosa at pH 6.8. Thus, the microspheres on oral administration, would release the
drug in colon, suggesting the potential of the hemocompatible copolymers for pH dependent colon targeted drug delivery system. 相似文献
67.
68.
To survey the frequency of Lyme borreliosis (LB) and to evaluate its clinical presentation in Europe, we performed a questionnaire interview of a sample of physicians involved in the care of patients with LB. Reference laboratories in 15 European countries agreed to participate by distributing questionnaires to those clinicians who most frequently requested LB serology for their patients. The mean number of cases of LB per physician per country showed a longitudinal geographical gradient, with a higher number of patients seen in Eastern and Central Europe than in Western Europe. Skin involvement was seen in 58.9% of the patients, neurological involvement in 34.3%, joint involvement in 15.4% and cardiac involvement in 2%. About 30% of the patients had multisystem involvement. The frequency of the different manifestations varied greatly between countries. The frequency of diagnosis of LB and the number of serological tests requested were inversely correlated. 相似文献
69.
Multi-output process identification 总被引:2,自引:0,他引:2
In model based control of multivariate processes, it has been common practice to identify a multi-input single-output (MISO) model for each output separately and then combine the individual models into a final MIMO model. If models for all outputs are independently parameterized then this approach is optimal. However, if there are common or correlated parameters among models for different output variables and/or correlated noise, then performing identification on all outputs simultaneously can lead to better and more robust models. In this paper, theoretical justifications for using multi-output identification for a multivariate process are presented and the potential benefits from using them are investigated via simulations on two process examples: a quality control example and an extractive distillation column. The identification of both the parsimonious transfer function models using multivariate prediction error methods, and of non-parsimonious finite impulse response (FIR) models using multivariate statistical regression methods such as partial least squares (PLS2), canonical correlation regression (CCR) and reduced rank regression (RRR) are considered. The multi-output identification results are compared to traditional single-output identification from several points of view: best predictions, closeness of the model to the true process, the precision of the identified models in frequency domain, stability robustness of the resulting model based control system, and multivariate control performance. The multi-output identification methods are shown to be superior to the single-output methods on the basis of almost all the criteria. Improvements in the prediction of individual outputs and in the closeness of the model to the true process are only marginal. The major benefits are in the stability and performance robustness of controllers based on the identified models. In this sense the multi-output identification methods are more ‘control relevant’. 相似文献
70.