Possibilities of nitric acid preparation of powder cellulose forms

For preparation of various modified forms of microcrystalline cellulose, an optional combination is proposed of hydrolytic activity with other properties of nitric acid such as, adduct forming ability (manifested as Knecht compound formation), oxidizing, bleaching and nitrating. The manifestation of a chosen acid function is reached by variation of the reaction conditions: concentration, temperature, time, etc. The sole-reagent continuous procedure involving several operations made in a predetermined sequence allows the use of a more simple technological scheme and saves energy, time and materials. The features of transformation of fibrous and microcrystalline forms of native cellulose into cellulose-II through the Knecht compound are discussed. Purely acidic transformation schemes of native cellulose into microcrystalline cellulose hydrate and amorphous low-nitrate powder cellulose according to the above scheme are considered. Morphological features as well as distinguishing properties — enhanced hydrophilicity, sorption activity and degree of whiteness — of the prepared materials are pointed out. The possibility of obtaining uniformly oxidized forms of powder cellulose according to this scheme and the outlook for the use of nitrogen(IV) oxide as a multifunctional reagent are discussed.     

Synthesis of glucoside compounds of ferrocenyl phenols and their antianemic activity

Six glucoside compounds have been synthesized by means of phase-transfer catalytic method and deacetylation from the starting material ferrocene. Their structures have been confirmed by elementary analysis, IR,¹HNMR and MS. The antianemic activities of some compounds have also been tested. Results indicate that these glucoside compounds possess the antianemic activities and therefore, the further study is well worth making. Supported by the foundation of Wuhan Metropolis Commission of Science and Technology Liu Huiying: born in 1937, Professor     

数控加工复合循环功能与子程序编程的特点及其应用

零件的数控加工,为了简化数控加工程序,既可以利用复合循环功能编程,又可以应用子程序技术编程.通过对复合循环功能编程与子程序编程的比较得知,应用子程序编程利大于弊,有利于保证零件的加工质量,提高加工效率,降低生产成本.     

Structure comparison between Th2Zn17-type and TbCu7-type Sm–Fe intermetallic compounds and their nitrides by means of 57Fe-Mössbauer spectroscopy

Samarium–iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th₂Zn₁₇-type and a TbCu₇-type structure, respectively. Structure comparison between these types was investigated for Sm–Fe intermetallic compounds and their nitrides by ⁵⁷Fe-Mössbauer spectroscopy.     

Effects of preheating on diaspore: Modifications in colour centres, structure and light emission

The thermal properties and thermal stability of diaspore-corundum (AlOOH-Al₂O₃), from Goian (Pontevedra, Spain) were studied by means of differential thermal analysis (DTA), thermogravimetry (TG), high temperature X-ray diffraction (HTXRD) and thermally stimulated luminescence (TL) techniques. The samples were annealed to link the combined effect of (i) dehydroxylation, (ii) oxidation-reduction of chromophores (Mn 0.5%, Fe₂O₃ 0.12%, TiO₂ 0.021% and Cr 80 ppm) determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and (iii) phase transitions whilst sample heating (i.e. α-AlOOH→α′-Al₂P₃→α-Al₂O₃). The blue colour of diaspore, attributed to the Ti⁴⁺-Fe²⁺ intervalence-charge-transfer mechanism, turns to white (circa 500 °C) in good agreement with the DTA endothermic peak (dehydroxylation). The coexistence of α-AlOOH and α′-Al₂P₃ phases has been detected by in situ HTXRD and could be correlated to the thermoluminescence tests performed on preheated aliquots (up to 500 °C).     

如何通过测量复摆的周期计算转动惯量

本文给出一种简约可行的方法,用来计算不规则物体绕任意轴转动时的转动惯量,同时,亦可定出质心轴位置.本文讨论的内容对教学有意义.     

双向中继网络中基于压缩感知的稀疏信道估计

为提高双向中继网络中稀疏信道估计的精度并减少训练序列的长度, 利用双向中继信道(Two-way Relay Channel, TWRC)的潜在稀疏特性, 研究了基于压缩感知的稀疏TWRC估计问题, 提出了一种改进的正交匹配追踪(Improved Orthogonal Matching Pursuit, IOMP)算法. 新算法运用迭代重加权最小二乘估计代替了正交匹配追踪(Orthogonal Matching Pursuit, OMP)算法中的最小二乘估计过程, 通过对样本进行迭代重加权, 逐步减小了异常样本的影响, 不断地修正了估计值, 在使用相同长度的训练序列时, 提高了估计的精度. 与传统的最小二乘估计算法相比, 新算法能够在获得相同估计效果的情况下, 显著减少所需训练序列的长度. 仿真结果验证了基于新算法的稀疏TWRC估计的有效性.     

Study of compound particle production in 84Kr-emulsion interactions at 1.7 A GeV

The characteristics of compound particle multiplicity distribution and multiplicity correlations between the compound particle and the grey particle, black particle, shower particle and heavily ionized track particle are investigated in this paper. It is found that the average multiplicities of the grey particle, black particle, shower particle and heavily ionized track particle increase with an increase in the number of compound particles, which can be explained by the impact geometrical model. The compound multiplicity distribution is observed to obey a Koba-Nielson-Olesen (KNO) type of scaling law.     

Central limit theorem for quadratic forms for sparse tables

Sufficient conditions for asymptotic normality for quadratic forms in {n_t − np_t} are given, where {n_t} are the observed counts with expected cell means {np_t}. The main result is used to derive asymptotic distributions of many statistics including the Pearson's chi-square.