提高微波功率源性能的一种新型控制系统

本控制系统用于抑制大功率速调管输出微波功率宏脉冲平顶波纹,改善电子直线加速器输出束流的品质.控制方法采用微分线性逼近和矩阵算法对系统的输入和输出进行分析,求出代表系统响应的传输矩阵,从而将复杂的激励一响应计算转化为简单的代数运算.实验结果显示出宏脉冲平项波纹得到了有效抑制,说明采用自适应前馈控制来获得平坦的宏脉冲平顶是切实可行的.     

o-quinone methides 2. Stereoselectivity in cycloaddition reactions of o-quinone methides with vinyl ethers

Cycloaddition reactions between vinyl ethers 3 and $\text{o}$-quinone methides 2, thermally generated from 2-hydroxybenzyl alcohols 1, have been studied. The structure and conformational preferences of the 4-substituted 2-ethoxy-(2,3)-dihydro-2$\text{H}$-benzopyrans 4–9 obtained, which show new interesting features, are discussed together with competitive kinetic data. The cycloaddition process is concerted and involves $\text{o}$-quinone methides in the $\text{E}$-configuration. The OEt-$\text{endo}$ transition state seems to be preferred with ethyl vinyl ether and $\text{Z}$-1-propenyl ethyl ether, whereas with $\text{E}$-1-propenyl ethyl ether the stereoselectivity of the cycloaddition process depends on substituents on the methylene group of the starting alcohol 1. These results are discussed in terms of $\text{endo}$ and $\text{exo}$ preference of the propenyl ether methyl group.     

Behaviour of silicon ointment for power-cable insulation under external heating

Journal of Thermal Analysis and Calorimetry - The burning process and typical fire parameters of power-cable silicon ointment were explored experimentally using a cone calorimeter, and the effects...     

Numerical Representations of Interval Orders

In the framework of the analysis of orderings whose associated indifference relation is not necessarily transitive, we study the structure of an interval order and its representability through a pair of real-valued functions. We obtain a list of characterizations of the existence of a representation, showing that the three main techniques that have been used in the literature to achieve numerical representations of interval orders are indeed equivalent.     

Electron Transport in Ga-Rich InxGa1-xN Alloys

Resistivity and Hall effect measurements on n-type undoped Ga-rich InxGa1-xN （0.06 ≤ x ≤ 0.135） alloys grown by metal-organic vapour phase epitaxy （MOVPE） technique are carried out as a function of temperature （15-350 K）. Within the experimental error, the electron concentration in Inx Ga1-x N alloys is independent of temperature while the resistivity decreases as the temperature increases. Therefore, Inx Ga1-xN （0.06 ≤ x ≤0.135） alloys are considered in the metallic phase near the Mort transition. It has been shown that the temperaturedependent metallic conductivity can be well explained by the Mort model that takes into account electron-electron interactions and weak localization effects.     

Novel versatile fullerene synthons.

We report the synthesis of three novel, versatile fullerene intermediates whose main feature is the presence of an amino end group. Simple condensation reactions of these intermediates under standard conditions produce new derivatives that are useful for applications in materials science and medicinal chemistry.     

Phonon anomalies in Co−Ni alloys

Summary A detailed experimental analysis of the inelastic crosssection along the [111]-direction in Co−Ni alloys is presented. Using a simple model and studying the cross-section as a function of both composition and temperature, it is shown that interesting information about the h.c.p.-f.c.c. transition can be gained in these alloys.

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Riassunto Nel presente lavoro si describe un’analisi sperimentale dettagliata della sezione d’urto anelastica dei neutroni lungo la direzione [111] in leghe Co−Ni. Impiegando un modello relativamente semplice e studiando la sezione d’urto in funzione di temperatura e concentrazione, si mostra che si possono ottenere utili informazioni riguardanti la transizione h.c.p.-f.c.c.

     

Continuous Utility Representation Theorems in Arbitrary Concrete Categories

In this paper the continuous utility representation problem will be discussed in arbitrary concrete categories. In particular, generalizations of the utility representation theorems of Eilenberg, Debreu and Estévez and Hervés will be presented that also hold if the codomain of a utility function is an arbitrary totally ordered set and not just the real line. In addition, we shall prove and apply a general result on the characterization of structures that have the property that every continuous total preorder has a continuous utility representation. Finally, generalizations of the utility representation theorems of Debreu and Eilenberg will be discussed that are valid if we consider arbitrary binary relations and allow a utility function to have values in an arbitrary totally ordered set.      

A wavelet-based methodology for monitoring thermoelastic structures

A wavelet-based methodology for detecting critical events in displacement and temperature histories, obtained by monitoring in-situ thermoelastic structures, is proposed. It is based on the wavelet analysis of thermoelastic potentials furnishing also the possibility to detect separately cases in which sudden jumps occur in the displacement history from those in which they occur on temperature history.