排序方式: 共有74条查询结果,搜索用时 15 毫秒
51.
3-Cyano-7-diethylamino-N-ethoxycarbonyl-iminocoumarin reacted with different hydrazines as N-nucleophiles to afford, in one step, a new series of 2-N-substituted 3-triazolonyl-iminocoumarins in good yields. In two cases, N-unsubstituted derivatives were also obtained. The structures of all the products obtained were confirmed by infrared, 1H NMR, 13C NMR, and elemental analysis. The optical properties of three of these compounds in dichloromethane and ethanol were reported. 相似文献
52.
In the present paper, a method is proposed for topology optimization of continuum structures subject to static and plastic admissibility conditions relative to a prescribed load. A key feature of the method is that, using a finite-element discretization, the form of the resulting topology optimization problem is similar to that of the direct static approach of the limit analysis problem. The proposed method is formulated in plane strain using Tresca materials and is illustrated on example problems taken from the literature. 相似文献
53.
Aris A Syntetos Mohamed Zied Babai Shuxin Luo 《The Journal of the Operational Research Society》2015,66(12):2061-2074
Intermittent demand items dominate service and repair inventories in many industries and they are known to be the source of dramatic inefficiencies in the defence sector. However, research in forecasting such items has been limited. Previous work in this area has been developed upon the assumption of a Bernoulli or a Poisson demand arrival process. Nevertheless, intermittent demand patterns may often deviate from the memory-less assumption. In this work we extend analytically previous important results to model intermittent demand based on a compound Erlang process, and we provide a comprehensive categorisation scheme to be used for forecasting purposes. In a numerical investigation we assess the benefit of departing from the memory-less assumption and we provide insights into how the degree of determinism inherent in the process affects forecast accuracy. Operationalised suggestions are offered to managers and software manufacturers dealing with intermittent demand items. 相似文献
54.
This article proposes the construction of Wigner measures in the infinite dimensional bosonic quantum field theory, with applications
to the derivation of the mean field dynamics. Once these asymptotic objects are well defined, it is shown how they can be
used to make connections between different kinds of results or to prove new ones.
Submitted: January 1, 2008., Accepted: July 1, 2008. 相似文献
55.
Zied Cheheb Fethi Albouchi Sassi Ben Nasrallah 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(4):620-635
This paper deals with a theoretical and an experimental study allowing the measurement of the radiative and the conductive properties of semitransparent materials. The method consists of applying a crenel heat flux on the front face of a semitransparent sample and recording the temperature at the rear face using an open thermocouple junction.Parameter identification is performed by the minimization of the ordinary least-squares function comparing the measured and the calculated temperatures. This later is obtained from the thermal model describing the heat transfer by conduction and radiation in the medium. This model is built by the thermal quadrupole formalism.Measurements are reported on commercial glasses and plexiglass samples, and the used iterative algorithm is based on the Gauss-Newton method. 相似文献
56.
Zied Bahroun Jean-Pierre Campagne 《Journal of Mathematical Modelling and Algorithms》2010,9(4):311-342
The growing quality and delay requirements have catalyzed the emergence of new commercial paradigms, which have strongly modified
the customer–supplier relationship. Customers and suppliers become more and more linked with contracts or global orders spanned
over a relatively important period. This paper, examines a type of contract which specifies a fixed and cyclic delivery dates
with delivery quantities varying between a min and a max values. The exact delivery quantities are usually known only few
days before the delivery. A company which produces n items on a bottleneck facility is considered; each item is confronted
to a cyclic demand and has an important holding cost in comparison to set-up costs. We propose heuristic approaches, to build,
in a medium term level, cyclic production schedules. These schedules face the demand and minimize a total cost function composed
of holding and set-up costs. An experiment is proposed in order to prove the effectiveness of our approaches. 相似文献
57.
Lithuanian Mathematical Journal - Abstract. This research paper stands for the estimation of the precision matrix of the normal matrix with monotone missing data. We explicitly provide maximum and... 相似文献
58.
Furano-Aliphatic copolyesters, such as poly(propylene furanic)-co-(polycaprolactone) (PPF-co-PCL), Poly(propylene furanic)-co-(polylactide) (PPF-co-PLA) and Poly(propylene furanic)-co-(polyglycolide) (PPF-co-PGA) were prepared by ring opening polymerization (R.O.P.) using monomers derived from renewable resources. These copolyesters were characterized by 1H-NMR, DSC and TGA. The degree of randomness determined by 1H-NMR is close to 1, reflecting a random distribution, sometimes less than one. This indicates that these polyesters have a character to block. The hydrolytic degradation of polymers was performed at pH 4.35 at 37°C over a period of four weeks. The oxidative degradation proved a mass loss of about 50%. 相似文献
59.
Scattering theory for the Nelson model is studied. We show Rosen estimates and we prove the existence of a ground state for the Nelson Hamiltonian. Also we prove that it has a locally finite pure point spectrum outside its thresholds. We study the asymptotic fields and the existence of the wave operators. Finally we show asymptotic completeness for the Nelson Hamiltonian. 相似文献
60.
Synthesis of benzopyrano[2,3-c]pyrazoles and 3-triazolonyliminocoumarins was successfully performed using heterocyclization of 3-cyano iminocoumarin or their N-ethoxycarbonylated derivatives with semicarbazide reagents. Elemental analysis, infrared, and 1H NMR spectral data confirmed the molecular structure of the newly synthesized compounds. 相似文献