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71.
Ivan Gutman Milan Randić Alexandru T. Balaban Boris Furtula Veselin Vuĉković 《Polycyclic Aromatic Compounds》2013,33(3):215-226
Abstract Recently three methods for calculating the π-electron content of rings of benzenoid hydrocarbons were put forward: one based on the consideration of Kekuléstructural formulas, and the other two based on an analogous treatment of the Clar aromatic sextet formulas. These three methods are applied to the homologous series consisting of two condensed acene chains (whose first members are pyrene, anthanthrene, peri-naphthacenonaphthacene, …), leading to basically identical results. In contrast to acenes (in which the partition of π-electrons into rings is uniform), in the double-hexagonal-chain species the partition of π-electrons is highly non-uniform. The electron content monotonically decreases, in opposite directions, along the two acene chains, being maximal in the least annelated rings. Some other generally valid regularities in the π-electron properties of the double–hexagonal–chain benzenoids are also pointed out. 相似文献
72.
Bernard Piechal Milan MrozowiczRoland Bohdan Filip Dyba?aWitold Trzeciakowski 《Optical Materials》2012,34(4):711-715
The changes of the optical power of Gradient Index (GRIN) lenses occurring in hydrostatic pressures of the range of 0-2 GPa are investigated. The measurements of the position of the waist of the semiconductor laser beam revealed the increase of the optical power of the lenses with increasing pressure. The use of the special plano-concave lenses insensitive to the changes of the refractive index of the pressure medium allowed to attribute the changes to the increasing index gradient in GRIN material. The effect has been explained within the frame of Mueller’s theory of photoelasticity. The findings have been then confirmed in experiments with the plano-planar and plano-convex lenses of the same materials. 相似文献
73.
Ivan Ostrovský Eva Pavlíková Jaroslav Blaško Renáta Górová Róbert Kubinec Milan Margetín Ladislav Soják 《International Dairy Journal》2009,19(9):545-549
The profile variations of approximately 70 fatty acids (FAs) in milk of ewes consuming total mixed rations (TMR) and grazing natural pasture were determined. Milk of ewes grazing pasture in May and September in the Slovak Republic contained 3-times more conjugated linoleic acid (CLA) (P < 0.001) and trans-vaccenic acid (TVA) (P < 0.001), and 2-times more α-linolenic acid (ALA) (P < 0.001) than that of ewes fed TMR. A doubling of the CLA and TVA contents of milk of ewes fed with TMR was achieved by changing to meadow hay containing a higher ALA content. Less availability of vegetation and lower ALA pasture content in summer (P < 0.001) caused a 2-fold decrease (P < 0.001) of CLA and TVA contents when compared with data obtained in May. With grass re-growth and an increase in pasture ALA content in September, the CLA and TVA contents rose to values similar to those obtained in May (P > 0.05). No significant differences in the FA composition in milk of ewes grazing on summer pasture at higher altitude were observed. 相似文献
74.
Milan R. Rapaić Tomislav B. Šekara 《Electrical Engineering (Archiv fur Elektrotechnik)》2011,93(2):91-102
This paper addresses the problem of discretization of fractional differintegrators and fractional systems in general. Two
new discretization schemes are proposed—optimal direct method, and computationally inexpensive indirect method. The proposed
methods are highly flexible and suitable for obtaining both general purpose and specialized, application-specific approximations.
Both proposed methods outperform recently proposed approximations, as it is shown in several illustrative examples. 相似文献
75.
Milan K. Jermář 《Water Resources Management》1989,3(4):299-313
This paper attempts to discover the real bottleneck of many irrigation projects: the complex of technical and nontechnical constraints which oppose the integrated and stable utilization of available soil and water resources. The efficiency of irrigation water use is the basic problem of intensive agriculture. Irrigation projects are, in the initial stage of operation, required to serve short-term objectives, such as to reach local self-sufficiency in food production. Their operation should, in the long run, nevertheless be based on a water-use concept and should reflect the desirable development of agriculture resulting from the need for further intensification and diversification of production. The establishment of the Water Management Strategy Plan for the Kirindi Oya Irrigation and Settlement Project in Sri Lanka is an example of the integrated approach to water resources development and management. This plan has been established on the basis of a multidisciplinary system analysis and simulation/optimization of the hydraulic and agricultural performance of the irrigation system. 相似文献
76.
Milan Vatovec Paul L. Kelley Tarek Alkhrdaji Antonio Nanni 《Canadian Metallurgical Quarterly》2002,6(3):184-193
The concrete-repair fiber reinforced polymer technology emerged in the United States during the past 10 years. Since 1995, carbon fiber reinforced polymer (CFRP) has been applied to strengthen concrete decks of a troubled posttensioned garage in Atlanta. During the construction of the garage, design deficiencies were found. A remedial repair, involving heavily?reinforced, 7.6 cm (3 in.) thick Gunite (Shotcrete) beams, applied to the underside of the slab between drop panels in the east-west (E-W) direction, was developed in 1984. Since then, delamination of Gunite beams and other structural problems repeatedly occurred. Epoxy injection and other limited repairs were done over the years in an attempt to remediate the problems. In 2000, due to the growing delamination concerns, backed up with nondestructive impact-echo testing results, and due to the newest set of structural analyses that showed additional design deficiencies, Simpson Gumpertz & Heger developed a new and comprehensive remedial program. The first phase of this program included an in-depth mechanical in?situ load test program to study the strength and stiffness performance of the existing typical slab spans, including the effects of Gunite beams, the loss of Gunite beams due to delamination, and the CFRP?strengthing of spans. The tests showed that the CFRP repair of E-W spans with delaminated Gunite beams is warranted and that it performs well. The performance of the existing typical spans in the north-south direction was found to be acceptable without any repairs. Further monitoring of the performance of Gunite beams is required, and additional CFRP strengthening will be done periodically. In addition, structural deficiencies of the typical second-level end bays were repaired using additional steel framing supports. 相似文献
77.
Overheating is a major problem in many modern buildings due to the utilization of lightweight constructions with low heat storing capacity. A possible answer to this problem is the emplacement of phase change materials (PCM), thereby increasing the thermal mass of a building. These materials change their state of aggregation within a defined temperature range. Useful PCM for buildings show a phase transition from solid to liquid and vice versa. The thermal mass of the materials is increased by the latent heat. A modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction. For realistic investigations, test rooms were erected where measurements were carried out under different conditions such as temporary air change, alternate internal heat gains or clouding. The experimental data was finally reproduced by dint of a mathematical model. 相似文献
78.
The joint effect of hydrogenation and preliminary plastic deformation (PPD) by tension and combined tension at 623 K on the
fracture stress of heat-resistant 15Kh2MFA steel is studied. Hydrogenation was performed both before and after the PPD. Using
transmission electron microscopy it was established that, independently of the type of loading and hydrogenation scheme, the
PPD decreases the distance between low-angle boundaries and increases the dislocation density in them and the disorientation
of the bainitic structure. The hydrogenation after the PPD does not influence the fracture stress of the steel. The PPD by
tension and combined tension of the preliminarily hydrogenated steel reduces its fracture stress proportionally to the increase
in the dislocation density in low-angle boundaries.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 118–121, May–June, 2008. 相似文献
79.
In this paper, we investigate the effect of employing a parametrized covariance function in a regression experiment on corresponding
optimum designs. We demonstrate these effects in the framework of a real example for measuring the lung’s retention of radioactive
particles. Also, two different covariance functions are considered, and it is shown that this choice can play a crucial role.
相似文献
80.