600MeV ~(18)O+~(nat)Pb(厚靶)系统生成Hg同位素独立产额测量(Ⅱ)结果与分析

报道了600MeV（18）O轰击（nat）Ph（厚靶）生成的质量数在180—209之间的Hg同位素产物独立截面的测量结果．通过与600MeV质子轰击天然铅靶生成Hg同位素产额分布的比较，讨论了几个质量区段Hg同位素的生成机制．测量结果也与相对论重离子碎裂反应双质子移出道的产额分布进行了比较．结果表明，中能重离子与中子较富集靶核组成的反应系统对生成丰中子类靶余核具有较明显的优势．     

矩阵在几何光学中的应用

本文中介绍了适用于几何光学中近轴光线的矩阵方法     

Invariant Subspaces for Semigroups of Algebraic Operators

T. Laffey showed (Linear and Multilinear Algebra6(1978), 269–305) that a semigroup of matrices is triangularizable if the ranks of all the commutators of elements of the semigroup are at most 1. Our main theorem is an extension of Hthis result to semigroups of algebraic operators on a Banach space. We also obtain a related theorem for a pair {A, B} of arbitrary bounded operators satisfying rank (AB−BA)=1 and several related conditions. In addition, it is shown that a semigroup of algebraically unipotent operators of bounded degree is triangularizable.     

Medium-range structural order in liquid Ni20Al80 alloy: Experimental and molecular dynamics studies

In this Letter, structural properties of liquid Ni₂₀Al₈₀ have been studied through molecular dynamics (MD) simulations, and results agree well with X-ray experiments. The prepeak in the structure factor manifests the existence of medium-range structural order (MRSO) in liquid Ni₂₀Al₈₀. Analyses in MRSO reveal the dominance of ideal icosahedra and defective icosahedra which, furthermore, form clusters and share common atoms.     

Principal components and spatial patterns of rain over Northern Italy, in relation to wind and geopotential fields

Summary A statistical study of precipitation over the Po Valley and the Alps during four winters, based on the application of a principal component (p.c.) method, exhibited a good correlation between the first three rotated eigenvectors of the cross-product matrix (between time series of data recorded at 70 stations) and three typical atmospheric circulation schemes over Northern Italy. The study is here continued, by relating these results to meteorological fields evaluated over a region wider than the area previously considered. Our attention mainly concentrated on the fields of time trend of geopotential height at 850 hPa over Europe, between latitude 34.5 and 51 degrees North and longitudes 0 and 21 degrees East. This was suggested by some peculiar relationships shown by the statistical distributions of geopotential height and wind direction and speed with respect to the first three p.c.’s. These relationships made us think of the possibility to use those trends as predictors of precipitation fields. Our analysis puts into evidence that three spatial patterns of geopotential, height time trend can be safely associated to the first three p.c.’s and, as a consequence, to the three precipitation modes corresponding to the spatial distributions of the eigenvectors, previously identified by us. They can therefore be considered meaningful precursors of precipitation field patterns over Northern Italy and Alpine regions.

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Riassunto Uno studio statistico della precipitazione sulla pianura padana e sulle Alpi durante quattro inverni, basato sull’applicazione del metodo delle componenti principali (c.p.), ha mostrato una buona correlazione fra i primi tre autovettori rotati della matrice dei prodotti incrociati (fra le serie temporali dei dati registrati in 70 stazioni) e tre tipici schemi di circolazione atmosferica sull’Italia del Nord. Lo studio viene qui prosequito, mettendo in relazione tali risultati con campi meteorologici valutati su una zona piú ampia di quella precedentemente considerata. La nostra attenzione si è prevalentemente concentrata sui campi di tendenza temporale dell’altezza di geopotenziale a 850 hPa sull’Europa, a latitudini comprese tra 34.5 e 51 gradi Nord e longitudini fra 0 e 21 gradi Est. Ciò è stato suggerito da alcune relazioni peculiari mostrate dalle distribuzioni statistiche di altezza di geopotenziale e di direzione ed intensità del vento rispetto alle prime tre c.p., che ci hanno fatto pensare alla possibilità di usare tali tendenze come predittori del campo di precipitazione. La nostra analisi ha messo in evidenza il fatto che tre distribuzioni spaziali di tendenza temporale del campo di altezza di geopotenziale possono essere con sicurezza associate alle prime tre c.p. e., quindi, ai tre modi di precipitazione corrispondenti alle distribuzioni spaziali degli autovettori precedentemente da noi identificati. Essi possono pertanto essere considerati significativi precursori del campo di precipitazione sull’Italia del Nord e sulle regioni alpine.

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Резюме Статистическое исследование выпадения осадков над долиной реки По и Альпами в течение четырех зим, основанное на применении метода главных компонент, обнаруживает хорошую корреляцию между первыми тремя вращающимися собственными векторами матрицы векторного произведения (между временными последовательностями данных, зарегистрированных на 70 станциях) и тремя схемами типичной атмосферной циркуляции над Северной Италией. В этой работе продолжены исследования. Полученные результаты связывайотся с метеорологическими полями, вычисленными над областью, которая шире ранее рассмотренной области. Главное внимание мы обращаем на поля временного хода для геопотенциальной высоты при 850гПа над Европой, между 34.5^щ и 51^щ северной широты и между 0^щ и 21^щ восточной долготы. Это следует из специальных соотношений, полученных с помощью статистических распределений геопотенциальной высоты и направления и скорости ветра относительно первых трех главных компонент. Эти соотношения позволяют нам использовать исследованные тенденции, как предсказатели полей вьшадения осадков. Нам анализ подтверждает, что три пространственным распределения временного хода для геопотенциальной высоты могут быть связаны с первыми тремя главными компонентами и, как следствие, с тремя моделями выцадения осадков, которые соответствуют пространственным распределениям собственных векторов, ранее идентифицированных в работе [Ш]. Следовательно, они могут рассматриватяся как предвестники для распределений полей осадков над Северной Италией и над Альпами.

     

Mössbauer study on LiFePO4 cathode material for lithium ion batteries

Crystalline LiFePO₄ has been synthesized using solid-state, spray pyrolysis, and wet chemical methods. The crystal parameters were obtained from Rietveld’s refinement methods of the X-ray diffraction patterns. A detailed investigation of the Fe valency carried out using Mössbauer spectroscopy at room temperature indicates that Fe is predominantly present in its bivalent state.     

Strongly countable dimensional compacta form the Hurewicz set

The hyperspaces of strongly countable dimensional compacta of positive dimension and of strongly countable dimensional continua of dimension greater than 1 in the Hilbert cube are homeomorphic to the Hurewicz set of all nonempty countable closed subsets of the unit interval [0,1]. These facts hold true, in particular, for covering dimension dim and cohomological dimension dimG, where G is any Abelian group.     

Study on effects of substrate temperature on growth and structure of alignment carbon nanotubes in plasma-enhanced hot filament chemical vapor deposition system

Alignment carbon nanotubes (ACNTs) were synthesized on silicon substrate coated with Ni catalyst film and Ta buffer layer by plasma-enhanced hot filament chemical vapor deposition using CH₄, NH₃, and H₂ as the reaction gas, and they were investigated by scanning electron microscopy and transmission electron microscopy. It is found that the diameter of the bamboo-structured ACNTs is increased from 62 to 177 nm when the substrate temperature was changed from 626 to 756 °C. Their growth rate is enhanced by the substrate temperature in a range of 626-683 °C and it is reversely reduced with the substrate temperature after the substrate temperature is over 683 °C. Beginning with wetting phenomenon, the effects of the substrate temperature on the structure and growth rate of the ACNTs are analyzed.     

An enantioselective Michael addition of malonate to nitroalkenes catalyzed by low loading demethylquinine salts in water

An enantioselective Michael addition of malonate to nitroalkenes is efficiently catalyzed by low loading demethylquinine salts in water; the yield range from 49% to 93% and the ee up to 90%.     

Almost-sure path properties of fractional Brownian sheet

The almost sure sample function behavior of the vector-valued fractional Brownian sheet is investigated. In particular, the global and the local moduli of continuity of the sample functions are studied. These results give precise information about the continuity and the oscillation behavior of the sample functions.