Mathematical modelling of hysteresis

Summary This paper presents a formal mathematical treatment of the general properties of scalar hysteretic systems. A generalization of the Preisach representation including both irreversible and reversible components of magnetization is given. It is shown that the Mayergoyz's theorem has a more general validity in this new representation. The effect of a linear feedback transformation on the existence of the generalized Preisach representation is considered, and the necessary and sufficient conditions for the invariance of such an existence are given. Finally the effect of the shape demagnetizing field on the relative weight of reversible and irreversible components of magnetization is discussed. The reversible component is found to be enhanced by the shape demagnetizing field. The results obtained in this paper are relevant not only for magnetic systems, but also for the mathematical modelling of any kind of hysteretic system.

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Riassunto In questo lavoro si presenta una trattazione matematica formale delle proprietà generali dei sistemi isteretici scalari. Si dà una generalizzazione del modello di Preisach che include entrambe le componenti irreversibile e reversibile della magnetizzazione. Si mostra come il teorema di Mayergoyz abbia una piú generale validità nella nuova rappresentazione. Si considera l'effetto di una trasformazione lineare di retroazione sull'esistenza del modello di Preisach generalizzato, e si danno le condizioni necessarie e sufficienti per l'invarianza di tale esistenza. Si esamina infine l'effetto del campo smagnetizzante sul peso relativo delle componenti reversibili e irreversibili della magnetizzazione. Si trova che il peso della componente reversibile cresce al crescere del fattore di smagnetizzazione. I risultati ottenuti sono di interesse non solo per i sistemi magnetici, ma anche per la modellizzazione matematica di qualsiasi sistema isteretico.

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Резюме В этой статье предлагается формалвное математическое рассмотрение общих свойств скалярных гистерезисных систем. Приводится обобщение представления Прейсака, включая необратимые и обратимые компоненты намагничивания. Показывается, что теория Майергойза имеет более широкую применимость в этом новом представлении. Приводятся необходимые и достаточные условия для инвариантности существования обобщенного представления Прейсака. В заключение, обсуждается влияние формы размагничивающего поля на относительный вес обратимых и необратимых компонент намагничивания. Получено, что обратимая компонента увеличивается благодаря форме размагничивающего поля. Полученные результаты в этой статье относятся не только к магнитным системам, но также для математического моделирования произвольных гистерезисных систем.

     

Polaronic correction to the exciton effective mass

Summary A significant correction to the value of the total exciton mass in polar materials results from the interaction of the electron and the hole with the longitudinal optical phonons. A procedure is given for computing this mass renormalization by means of the excitonic-polaron theory; numerical results are obtained for many substances. Evidence for this effect is found from a detailed analysis of experimental polariton dispersion data.

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Riassunto Una correzione significativa al valore della massa totale dell'eccitone si produce nei cristalli polari a causa dell'interazione dell'elettrone e della buca con i fononi ottici longitudinali. Si fornisce un procedimento per calcolare la rinormalizzazione della massa totale dell'eccitone estendendo la teoria dell'eccitone polaronico al caso d'impulso diverso da zero; si ottengono risultati numerici per un gran numero di sostanze polari. L'evidenza sperimentale di questo effetto è trovata mediante un'analisi dettagliata di dati sperimentali sulla dispersione spaziale dei polaritoni.

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Резюме В полярных кристаллах взаимодействе злектрона и дыры с продольными оптическими фононами производит значительное изменение значения полной массы экситона. Предлогается метод для вычисления перенормализации полной массы экситона при помощи распространеия теории поляритоного экситона на случай ненулевого импулса. Численные результаты получены для болыщого числа вещества. Экспериментальное выявление этого эффекта получено при помощи детального анализа экспериментальных данных п простраственной дисперсии поляритонов.

     

Calculation of the external quality factor of the high power input coupler for the BEPC Ⅱ superconducting cavity

It is very important to predict the coupling between the cavity and the high power input source in the coupler design. In this paper, a time domain method is used to calculate the external quality factor Qext for the BEPC Ⅱ superconducting cavity. A comparison between simulation results and experimental results is presented. The results of simulation and measurement of Qext have a good agreement within an error of 10%.The geometry parameters related with Qext are also studied.     

Analysis of the positive or negative lateral shift of the reflected beam in Otto configuration under grazing incidence

We investigate the lateral shift of a TM-polarized light beam reflected from Otto configuration under grazing incidence. It is found that the lateral shift is strongly dependent on the thickness of the air-gap layer. By employing the pole-null representation, we demonstrate that the lateral shift is closely related to the null of the reflection function. The numerical simulations for a Gaussian beam are performed to demonstrate the validity of our theoretical analysis.     

Short and long consecutive pairs model in the interpretation of MFE and F-ODMR experiments in molecular crystals

We have presented a model of two consecutive pairs of triplet excitons, which consists of a succession of two pairs known as short pair and long pair with reference to their respective lifetimes. We have applied this model to the modulation of prompt fluorescence (PF) in crystalline tetracene by a static magnetic field (MFE) and a microwave field (F-ODMR). The two types of experiments have been enough perfectly reproduced by using the same set of kinetics constants. Thus, we have arrived to rise the inconsistencies which one reproached the Seventies kinetic model.     

Polaron effects on excitons in parabolic quantum wells: fractional-dimension variational approach

Polaron effects on excitons in parabolic quantum wells are studied theoretically by using a variational approach with the so-called fractional dimension model. The numerical results for the exciton binding energies and longitudinal-optical phonon contributions in GaAs/Al_0.3Ga_0.7As parabolic quantum well structures are obtained as functions of the well width. It is shown that the exciton binding energies are obviously reduced by the electron (hole)-phonon interaction and the polaron effects are un-negligible. The results demonstrate that the fractional-dimension variational theory is effectual in the investigations of excitonic polaron problems in parabolic quantum wells.     

Investigation of surface entropy for liquid less simple metals

We have derived an efficient expression in closed form for the surface entropy of liquid metals from the statistical mechanical theory of zeroth order involving hard sphere model interaction. Using this expression we have investigated the surface entropy for liquid less simple metals namely Zn, Cd, In, Sn, Pb, Sb, Tl and Bi selfconsistently. The effective hard sphere diameters are obtained from the thermodynamic perturbation theory called the LWCA. The prediction of the selfconsistent calculation improves significantly for all concerned systems except for Zn and Cd. The underlying cause of discrepancy for Zn and Cd is also discussed.     

VP-16诱导的鼻咽癌细胞亚系多药耐受表型的研究

经VP-16 大剂量短暂冲击加递增低浓度诱导方法建立了鼻咽癌耐药细胞亚系LCE/VP.用RT-PCR和FCM 免疫荧光法检测了耐药基因MRP和m dr1 在m RNA 水平和蛋白质水平的表达,并用MTT 法测定了LCE/VP对9 种化疗药物的敏感试验. 结果发现LCE/VP细胞MRP和m dr1 在m RNA水平均有表达,且前者明显高于后者,蛋白质水平的表达情况与m RNA 水平相一致;LCE/VP对9 种化疗药物中的6 种药物敏感程度均有不同倍数的增加. 这表明LCE/VP呈典型的MDR表型,并有耐药基因MRP和m dr1 的共表达,其中MRP起主要作用     

Dn Basic Hypergeometric Series

We study multiple series extensions of basic hypergeometric series related to the root system D_n. We make a small change in the notation used for C_n and D_n series to bring them closer to A_n series. This allows us to combine the three types of series, and get D_n extensions of the following classical summation and transformation theorems: The q-Pfaff-Saalschütz summation, Rogers' _{6 5} sum, the q-Gauss summation, q-Chu-Vandermonde summations, Watson's q-analogue of Whipple's transformation, and the q-Dougall summation theorem. We also define A_n and C_n extensions of the Rogers-Selberg function, and prove a reduction formula for both of them. This generalizes some work of Andrews. We use some techniques originally developed to study multiple basic hypergeometric series related to the root system A_n (U(n + 1) basic hypergeometric series).