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21.
Different ammonium fluoroferrates (NH4)xFeF2x (2≤x≤3) have been investigated. The thermal decomposition of the compounds obtained can be interpreted by their identical crystal structures (cryolite type). The decomposition products of all ammonium fluoroferrates formed in initial stage are isostructural of NH4FeF4. The decomposition is accompanied by the partial reduction of Fe(III) to Fe(II) by ammonium isolated. The end product of the thermal decomposition is FeF2 and FeF3 mixture.  相似文献   
22.
Solid solutions NaCl—CdCl2 were studied in an interval of CdCl2 concentrations of 0.05—3 mol.% by Raman spectroscopy. The molecular form Na2CdCl4 decomposes: Na2CdCl4 2Na+ + Cd2+ + 2Cl2 + 2e; 2Na + 2e 2Na0. Free sodium atoms form color centers of crystal (F centers) in the region of jumpwise changing the partition coefficient of CdCl2 in NaCl (K jump).  相似文献   
23.
Summary 2-Acetoxy- and 2-Hydroxy-2,3-dihydronaphtho[1,8-bc]pyranes were synthesized by decomposition of 1-hydroperoxy-1,2-dihydroacenaphthylene in acetic acid in the presence of perchloric acid.
Synthese von 2-Acetoxy- und 2-Hydroxy-2,3-dihydronaphtho[1,8-bc]pyran
Zusammenfassung 2-Acetoxy- und 2-Hydroxy-2,3-dihydronaphtho[1,8-bc]pyrane konnten durch Zersetzung von 1-Hydroperoxy-1,2-dihydroacenaphthylen in Essigsäure in Anwesenheit von Perchlorsäure synthetisiert werden.
  相似文献   
24.
特征线谱提取是舰船目标识别的一个重要研究环节,常采用传统的DEMON谱分析方法,处理过程中,一般对舰船噪声时域信号未予抑噪,低信噪比情况下,传统DEMON谱分析性能差。对此,提出一种采用遗传算法优化变分模态分解方法,用于分解舰船噪声原时域信号,获得抑制噪声后的舰船噪声重构信号,进而有效提取了舰船目标噪声幅度调制特征线谱。该方法首先采用遗传算法优化变分模态分解的两个关键输入参数(分解所取模态个数和惩罚因子),对变分模态分解得到的各阶固有模态分量加以判别,去除噪声主导分量,保留信号主导分量,使重构舰船噪声信号显著抑制了干扰噪声,然后对降噪后的重构信号进行频谱分析,获得目标噪声调制特征线谱。理论分析、仿真和实验数据处理结果表明,相比传统DEMON谱分析法,基于遗传算法优化变分模态分解的舰船噪声特征线谱提取方法具有更好的噪声抑制能力,所获取的舰船噪声幅度调制特征线谱信噪比明显高于传统DEMON方法,具有一定优势,前景良好。  相似文献   
25.
Nowadays, the use of hybrid structures and multi-component materials is gaining ground in the fields of environmental protection, water treatment and removal of organic pollutants. This study describes promising, cheap and photoactive self-supported hybrid membranes as a possible solution for wastewater treatment applications. In the course of this research work, the photocatalytic performance of titania nanowire (TiO2 NW)-based hybrid membranes in the adsorption and degradation of methylene blue (MB) under UV irradiation was investigated. Characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffractometry (XRD) were used to study the morphology and surface of the as-prepared hybrid membranes. We tested the photocatalytic efficiency of the as-prepared membranes in decomposing methylene blue (MB) under UV light irradiation. The hybrid membranes achieved the removal of MB with a degradation efficiency of 90% in 60 min. The high efficiency can be attributed to the presence of binary components in the membrane that enhanced both the adsorption capability and the photocatalytic ability of the membranes. The results obtained suggest that multicomponent hybrid membranes could be promising candidates for future photocatalysis-based water treatment technologies that also take into account the principles of circular economy.  相似文献   
26.
张林进  叶旭初 《应用化学》2009,26(6):697-701
以氯化锶和硼酸氢铵为原料,采用液相沉淀法制备了片状水合硼酸锶(SrB6O10•5H2O)粉体,并用XRD、FT-IR及SEM进行了表征。利用热重分析法对片状纳米硼酸锶粉体的脱水热分解动力学进行了研究,分别采用 Coats- Redfern 方程和 Flynn-Wall-Ozawa(FWO)法对热重分析数据进行了处理和拟合,初步确定了水合硼酸锶的四步脱水过程及相应的热分解反应机理,得到各步反应的表观活化能和指前因子。  相似文献   
27.
On the convergence of cross decomposition   总被引:2,自引:0,他引:2  
Cross decomposition is a recent method for mixed integer programming problems, exploiting simultaneously both the primal and the dual structure of the problem, thus combining the advantages of Dantzig—Wolfe decomposition and Benders decomposition. Finite convergence of the algorithm equipped with some simple convergence tests has been proved. Stronger convergence tests have been proposed, but not shown to yield finite convergence.In this paper cross decomposition is generalized and applied to linear programming problems, mixed integer programming problems and nonlinear programming problems (with and without linear parts). Using the stronger convergence tests finite exact convergence is shown in the first cases. Unbounded cases are discussed and also included in the convergence tests. The behaviour of the algorithm when parts of the constraint matrix are zero is also discussed. The cross decomposition procedure is generalized (by using generalized Benders decomposition) in order to enable the solution of nonlinear programming problems.  相似文献   
28.
Let X1, …, Xn be independent random variables and define for each finite subset I {1, …, n} the σ-algebra = σ{Xi : i ε I}. In this paper -measurable random variables WI are considered, subject to the centering condition E(WI ) = 0 a.s. unless I J. A central limit theorem is proven for d-homogeneous sums W(n) = ΣI = dWI, with var W(n) = 1, where the summation extends over all (nd) subsets I {1, …, n} of size I = d, under the condition that the normed fourth moment of W(n) tends to 3. Under some extra conditions the condition is also necessary.  相似文献   
29.
Let M be a n-dimensional simply connected, complete Riemannian manifold with constant negative curvature. The heat kernel on M is denoted by H^M_t(x, y) = H^M_t(r(x, y)), where r(x, y) = dist(x, y). We have the explicit formula of H^M_t(x, y) for n=2, 3, and the induction formula of H^M_t(x, y) for n ≥ 4^{[-1]}. But the explicit formula is very complicated for n ≥ 4. ln this paper we give some simple and useful global estimates of H^M_t(x, y), and apply these estimates to the problem of eigenvalue.  相似文献   
30.
I. Atencia  P. Moreno 《TOP》2003,11(2):285-310
We analyse a single-server retrial queueing system with infinite buffer, Poisson arrivals, general distribution of service time and linear retrial policy. If an arriving customer finds the server occupied, he joins with probabilityp a retrial group (called orbit) and with complementary probabilityq a priority queue in order to be served. After the customer is served completely, he will decide either to return to the priority queue for another service with probability ϑ or to leave the system forever with probability =1−ϑ, where 0≤ϑ<1. We study the ergodicity of the embedded Markov chain, its stationary distribution function and the joint generating function of the number of customers in both groups in the steady-state regime. Moreover, we obtain the generating function of system size distribution, which generalizes the well-knownPollaczek-Khinchin formula. Also we obtain a stochastic decomposition law for our queueing system and as an application we study the asymptotic behaviour under high rate of retrials. The results agree with known special cases. Finally, we give numerical examples to illustrate the effect of the parameters on several performance characteristics.  相似文献   
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