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991.
To analyze the isotonic regression problem for normal means, it is usual to assume that all variances are known or unknown but equal. This paper then studies this problem in the case that there are no conditions imposed on the variances. Suppose that we have data drawn fromkindependent normal populations with unknown meansμi's and unknown variancesσ2i's, in which the means are restricted by a given partial ordering. This paper discusses some properties of the maximum likelihood estimates ofμi's andσ2i's under the restriction and proposes an algorithm for obtaining the estimates. 相似文献
992.
师同顺 《光谱学与光谱分析》1998,18(3):293-297
研究了香兰素对甲苯胺希夫碱及其金属配合物在3800-200 cm^-1范围的傅里叶变换红外光谱光谱,对主要谱带进行了经验归属。 相似文献
993.
Shi Yingguang 《数学年刊B辑(英文版)》1983,4(2):227-230
In this paper the author discusses a problem of Chebyshev approximation by linear alternating families with fixed values at nodes and gives the analogues of all results for the classical Chebyshev approximation, which include the theorems on existence, alternation, uniqueness, strong uniqueness and the continuty of the best approximation operator, etc. 相似文献
994.
995.
Shi W Shafaei-Fallah M Anson CE Rothenberger A 《Dalton transactions (Cambridge, England : 2003)》2005,(24):3909-3912
The investigation presents new synthetic methods for the generation of tripodal P/S ligands by reactions of metal alkoxides and carboxylates with the organoperthiophosphinic acid anhydride Lawesson's reagent. Four new transition-metal complexes containing various tripodal ligand sets were synthesised and characterised. 相似文献
996.
In situ self-assemblies of new biodegradable triblock PLLA-b-PBS-b-PLLA and PDLA-b-PBS-b-PDLA have been investigated in acetonitrile solution. At first, two series of PLLA-b-PBS-b-PLLA and PDLA-b-PBS-b-PDLA, respectively denoted as the P and Q triblock copolyester series, were prepared with fixed PBS block ((overline) M(n,NMR) = 6.9 kDa) and diverse enantiomeric PLLA/PDLA blocks. Further, their chemical structures and thermal properties were characterized by means of titration, nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), polarimeter, wide-angle X-ray diffraction (WAXD) and thermal analytical instruments. When mixing the synthesized enantiomeric copolyester pairs denoted as P(1)/Q(1) - P(8)/Q(8) in acetonitrile solution at 60 degrees C, in situ self-assemblies were found to happen for the P(4)/Q(4) to P(8)/Q(8) pairs, bearing longer enantiomeric PLA block lengths. DSC and WAXD analysis of the self-assembled microparticles demonstrated that PLLA/PDLA racemic crystals were formed for the P(5)/Q(5) - P(8)/Q(8) systems, as evidenced by their melting points over 200 degrees C, and a new X-ray diffraction peak detected at 2theta = 11.8 degrees . Moreover, morphological studies by scanning electron microscopy (SEM) indicated the formation of disk- or platelet-like microparticles. It was noted that the diameters of the microparticles self-assembled in situ decreased from 1.28-1.50 mum down to 480-660 nm, through tailoring the enantiomeric PLA block length. Other factors, such as a central PBS block, the enantiomeric block length and the preparation conditions were suggested to play important roles in the in situ self-assembly of these enantiomeric triblock copolyesters. These results provide a facile way to self-assemble hydrophobic, biodegradable microparticles, through tuning the important van der Waals stereocomplexation interactions between two enantiomeric blocks in solution. 相似文献
997.
Tian CS Qian D Wu D He RH Wu YZ Tang WX Yin LF Shi YS Dong GS Jin XF Jiang XM Liu FQ Qian HJ Sun K Wang LM Rossi G Qiu ZQ Shi J 《Physical review letters》2005,94(13):137210
The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation. 相似文献
998.
A new structural phase transition has been observed at low temperature for the one-third of a monolayer (alpha phase) of Pb on Ge(111) using a variable-temperature scanning tunneling microscope. The well-known (sqrt[3] x sqrt[3])R30 degrees to (3 x 3) transition is accompanied by a new structural phase transition from (3 x 3) to a disordered phase at approximately 76 K. The formation of this "glasslike" phase is a consequence of competing interactions on different length scales. 相似文献
999.
The structure of K-doped fullerene peapods has been investigated by means of high-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS). It is proven that the potassium atoms can be doped at the intermolecular sites within C60 peapods. The EELS spectrum of potassium (K) L edge clearly exhibits the feature of K+ in the doped peapod and consequently suggests n-type doping. These results encourage the realization of a one-dimensional superconducting wire based on the nanotube peapods. 相似文献
1000.
A three-dimensional optical data storage system that combines a new recording material with a microholographic data format in which data are stored as single-bit microholograms is presented. This format offers less sensitivity to environmental conditions than the page-based holographic approach in addition to an increased compatibility with current storage technologies. The new recording material is based on a thermoplastic material. The results presented indicate that the dimensions of the microholograms are larger than those calculated by use of simple laser beam waist approximations and that multiple layers of microholograms would significantly affect signal levels. Data densities achievable with the microholographic format will likely be limited by those effects. 相似文献