LEONARDO DA VINCI AND FLUID MECHANICS 1)

旷世全才列奥纳多·达·芬奇(Leonardo da Vinci),被世人誉为画家、雕刻家、天文学家、发明家、音乐家、数学家、解剖学家、生理学家、地质学家、植物学家、作家、军事、建筑工程和制图师,是意大利文艺复兴时期人文主义的代表人物。本文对其流体力学相关思想及湍流、飞行、波浪和风暴等几个方面的研究贡献进行梳理,认为他是流体力学科学研究的先驱和奠基人,也是一位“流体力学家”。     

追念钱临照先生--《钱临照文集》读后感

文章叙述了钱临照教授的科学生涯，展示了他对物理学所作的主要贡献和对现代中国科学和教育事业的发展所起的重要作用。文中也包含了作者的一些个人回忆。     

Point-source spark shadowgraphy at the historic birthplace of supersonic transportation

About a decade after its foundation, the most advanced ballistics laboratory in Germany at the time, the Kruppsche Schiessplatz, was utilized by Ernst Mach in 1888. His intent was to validate his pioneering shock wave research using military shells as supersonic vehicles. The 125th anniversary of the Schiessplatz was celebrated in 2002. Along with Machs research, it served to initiate the field of supersonic transportation technology. The specific subject of this paper is the application of point-source spark shadowgraphy at the same laboratory in the 1970s to visualize gas flow over aeroballistic projectiles. However, different from Machs original interest, the new purpose of spark photography at that time in the ballistic ranges of the German Bundeswehr was to find technical solutions to aeroballistic problems when field-testing gave incomplete answers. Both a qualitative and a quantitative understanding of the principles of aeroballistics were sought in this research.Received: 3 February 2003, Accepted: 30 June 2003, Published online: 2 September 2003An abridged version of this paper was presented at the 13th American Physical Society Topical Conference on Shock Compression of Condensed Matter at Portland, Oregon, from July 20 to 25, 2003     

Moduli of convexity and smoothness of reflexive subspaces of L

We show that for any probability measure μ there exists an equivalent norm on the space L¹(μ) whose restriction to each reflexive subspace is uniformly smooth and uniformly convex, with modulus of convexity of power type 2. This renorming provides also an estimate for the corresponding modulus of smoothness of such subspaces.     

Condensed Cramer rule for some restricted quaternion linear equations

In this paper, we derive an alternative more condensed Cramer rule for the unique solution of some restricted left and right systems of quaternion linear equations. The findings of this paper extend some known results in the literature.     

On the modulus of -convexity

In this paper, we prove that the moduli of W^*-convexity, introduced by Ji Gao [J. Gao, The W^*-convexity and normal structure in Banach spaces, Appl. Math. Lett. 17 (2004) 1381–1386], of a Banach space X and of the ultrapower of X itself coincide whenever X is super-reflexive. Moreover, we improve a sufficient condition for uniform normal structure of the space and its dual. This generalizes and strengthens the main results of [J. Gao, The W^*-convexity and normal structure in Banach spaces, Appl. Math. Lett. 17 (2004) 1381–1386].     

On k-networks and weak bases for spaces

In this paper, we answer some problems on k-networks and weak bases posed by Liu and Tanaka (2007) [19].     

Charge dynamics and optical properties of layered cobaltates

We study the charge dynamics and electronic structure by optical spectroscopy technique. Here we focus on the following four issues: (1) the evolution of optical spectra with Na content; (2) the spectral features specific to different regions in the phase diagram; (3) the c-axis optical response for crystal at the A-type antiferromagnetic region; (4) the optical response of misfit-layered Bi₂M₂Co₂O_y (M=Ba, Sr, Ca) and Ca₃Co₄O_y single crystals.     

The poset structures admitting the extended binary Golay code to be a perfect code

Brualdi et al. [Codes with a poset metric, Discrete Math. 147 (1995) 57-72] introduced the concept of poset codes, and gave an example of poset structure which admits the extended binary Golay code to be a 4-error-correcting perfect P-code. In this paper we classify all of the poset structures which admit the extended binary Golay code to be a 4-error-correcting perfect P-code, and show that there are no posets which admit the extended binary Golay code to be a 5-error-correcting perfect P-code.