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排序方式: 共有172条查询结果,搜索用时 15 毫秒
21.
Murat Taş Seval Çamur Yalçın Kılıç 《Journal of Thermal Analysis and Calorimetry》2011,103(3):995-1000
The complexes were synthesized by the reaction between sodium salt of p-aminosalicylic acid (PAS) and Cu(II) for 1 and corresponding ethylenediamine (en) or its derivatives for 2–6. The complexes were characterized by using elemental analyses, FT-IR, UV–Vis, magnetic moment measurements, and thermal analyses
techniques. In complex 1[Cu2(PA)4(H2O)2], two Cu(II) ions were found as bridged by four μ-O:O′ p-aminosalicylato (PA) ligands, forming a cage structure, and two aqua ligands to form dinuclear square-pyramidal geometry
around Cu(II) ions. In the complexes 2–6, the PA (anionic form of p-aminosalicylic acid) coordinated to Cu(II) ions as monodentate manner by using its oxygen atom of deprotonated carboxylic
acid and ethylenediamine derivatives coordinated to the Cu(II) ions in bidentate manner to form mononuclear octahedral complexes
[Cu(PA)2(L)2] (L = ethylendiamine, N,N-dimethylethylendiamine, N,N′-dimethylethylendiamine, N,N,N′,N′-tetramethylethylendiamine, and 1,3-propanediamine, for complexes 2, 3, 4, 5, and 6, respectively). In all the complexes OH and NH2 groups of PA ligands were not coordinated to metals. 相似文献
22.
Robert Leon Jerrard Halil Mete Soner 《Archive for Rational Mechanics and Analysis》1998,142(2):99-125
(Accepted August 19, 1996) 相似文献
23.
Let R be a ring with identity. A module \(M_R\) is called an r-semisimple module if for any right ideal I of R, MI is a direct summand of \(M_R\) which is a generalization of semisimple and second modules. We investigate when an r-semisimple ring is semisimple and prove that a ring R with the number of nonzero proper ideals \(\le \)4 and \(J(R)=0\) is r-semisimple. Moreover, we prove that R is an r-semisimple ring if and only if it is a direct sum of simple rings and we investigate the structure of module whenever R is an r-semisimple ring. 相似文献
24.
We study a Merton type optimization problem under a reallocation constraint. Under this restriction, the stock holdings can
not be liquidated faster than a certain rate. This is a common restriction in certain type of investment firms. Our main objective
is to study the large time optimal growth rate of the expected value of the utility from wealth. We also consider a discounted
infinite horizon problem as a step towards understanding the first problem. A numerical study is done by solving the dynamic
programming equations. Under the assumption of a power utility function, an appropriate dimension reduction argument is used
to reduce the original problem to a two dimensional one in a bounded domain with convenient boundary conditions. Computation
of the optimal growth rate introduces additional numerical difficulties as the straightforward approach is unstable. In this
direction, new analytical results characterizing the growth rate as the limit of a sequence of finite horizon problems with
continuously derived utility are proved. 相似文献
25.
We consider the combined hubbing and routing problem in postal delivery systems and develop an iterative two-stage solution
procedure for the problem. In the first stage, hub locations are determined and postal offices are multiply allocated to the
hubs. The second stage gives the routes in hub regions that alter the distances between points used in the hub-location problem.
The procedure then iterates between two stages by updating the distances used in hubbing in order to produce a route-compatible
hub configuration. Computational experience is reported for the test problems taken from the literature. For a case study
Turkish postal delivery system data are utilized. As the case study is applied on a road network, a final stage, seeking improvements
based on special structures in the routed network, is appended to the two-stage solution procedure. 相似文献
26.
Alain Bensoussan Lama Moussawi-Haidar Metin Çakanyıldırım 《Annals of Operations Research》2010,181(1):603-640
This paper analyzes a stochastic inventory problem with an order-time constraint that restricts the times at which a manufacturer
places new orders to a supplier. This constraint stems from the limited upstream capacity in a supply chain, such as production
capacity at a supplier or transportation capacity between a supplier and a manufacturer. Consideration of limited upstream
capacity extends the classical inventory literature that unrealistically assumes infinite supplier/transporter capacity. But
this consideration increases the complexity of the problem. We study the constraint under a Poisson demand process and allow
for a fixed ordering cost. In presence of the constraint, we establish the optimality of an (s,S) policy under both the discounted and average cost objectives. Under the average cost objective, we show the uniqueness of
the order-up-to level S. We numerically compare our model with the classical unconstrained model. We report significant savings in costs that can
be achieved by using our model when the order time is constrained. 相似文献
27.
Ce1?xErxO2 and Ce1?2xErxGdxO2 co-doped ceria electrolyte nanopowder materials were successfully prepared by sol–gel method. Depending on the temperature, the crystal structure changes were analyzed by X-ray diffraction. It was observed that the crystal size of the electrolytes decreased depending on the temperature and the time. X-ray diffraction results confirmed cubic fluorite structure in the samples. The microstructural properties of the samples were analyzed by scanning electron microscopy, and thermal stability measurement was performed by thermogravimetric and differential thermal analyses. The total electrical conductivity of the nanopowder electrolytes was determined by the dc four-point probe technique in air at temperatures ranging from room temperature to 1373 K. The four-probe conductivity results revealed that Ce0.8Er0.1Gd0.1O2 has a higher ionic conductivity compared to Ce0.83Er0.17O2 at 1123 K. The four-probe conductivity results show that both Ce1?xErxO2 and Ce1?2xErxGdxO2 solid electrolytes have potential application to oxide ionic conductor for solid oxide fuel cells. 相似文献
28.
Natural diatomaceous earth (DE) is modified by flux calcination and refluxing with acid. To characterize natural DE, modified DE's [flux calcinated (FC)DE and FCDE-I] and silica gel 60GF(254) (Si-60GF(254)) are analyzed microscopically, physically, and chemically by various techniques. FCDE-I and Si-60GF(254) are investigated for their usefulness in the stationary phase of thin layer chromatography (TLC) both individually and in composition. Sodium diethyldithiocarbamate (DEDTC) and ammonium pyrrolidinedithiocarbamate (PyDTC) are prepared as Co or Cu (M) complexes [M(DEDTC)(2) and M(PyDTC)(2), respectively]. These complexes and their mixtures are run on thin layers of Si-60GF(254) and FCDE-I individually, and on various FCDE-I and Si-60GF(254) mixtures. Pure toluene and various toluene-cyclohexane mixtures (3:1, 1:1, 1:2, 1:3, v/v) are used as mobile phases for the running the complexes. The best analytical separations of both M(DEDTC)(2) and M(PyDTC)(2) complexes are obtained when using pure toluene and toluene-cyclohexane (3:1, 1:1, v/v) as mobile phases on FCDE-I-Si-60GF(254) (1:3, 1:1, w/w) layers as stationary phases. This study shows that it is possible to qualitatively analyze and to satisfactorily separate a mixture Cu(2+) and Co(2+) cations on cited chromatographic systems. 相似文献
29.
Mahmut Ulusoy Hasan Karabıyık Rafet Kılınçarslan Muhittin Aygün Bekir Çetinkaya Santiago García-Granda 《Structural chemistry》2008,19(5):749-755
Copper(II) and cobalt(II) complexes of salicylaldimine obtained by the condensation of N,N-diethyl-2-methyl-1,4-phenylenediamine with 3,5-di-tert-butyl-2-hydroxybenzaldehyde have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements,
cyclic voltammetry, and FT-IR and UV–Vis spectroscopy. The molecular structure of the title copper(II) complex was determined
by the single crystal X-ray diffraction technique. The Cu(II) center is coordinated by four atoms of the donor set in a compressed
tetrahedral trans-[N2O2] environment, which can be essentially ascribed to the presence of bulky fragments of the ligand. The computed bond valences
of the copper verify +2 oxidation state and indicate that the copper bonds, in particular Cu–N bonds, are elongated due to
steric effects from bulky substituents in the ligands, N-(4-diethylamino-2-methylphenyl). Intermolecular C–H···π interactions leading to centrosymmetric synthons serve to stabilize
periodic organization of the molecules. 相似文献
30.
Detection of Variation in Long-Term Micropropagated Mature Pistachio via DNA-Based Molecular Markers
Hülya Akdemir Veysel Suzerer Engin Tilkat Ahmet Onay Yelda Ozden Çiftçi 《Applied biochemistry and biotechnology》2016,180(7):1301-1312
Determination of genetic stability of in vitro-grown plantlets is needed for safe and large-scale production of mature trees. In this study, genetic variation of long-term micropropagated mature pistachio developed through direct shoot bud regeneration using apical buds (protocol A) and in vitro-derived leaves (protocol B) was assessed via DNA-based molecular markers. Randomly amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR), and amplified fragment length polymorphism (AFLP) were employed, and the obtained PIC values from RAPD (0.226), ISSR (0.220), and AFLP (0.241) showed that micropropagation of pistachio for different periods of time resulted in “reasonable polymorphism” among donor plant and its 18 clones. Mantel’s test showed a consistence polymorphism level between marker systems based on similarity matrices. In conclusion, this is the first study on occurrence of genetic variability in long-term micropropagated mature pistachio plantlets. The obtained results clearly indicated that different marker approaches used in this study are reliable for assessing tissue culture-induced variations in long-term cultured pistachio plantlets. 相似文献