Estimating functions for jump–diffusions

Asymptotic theory for approximate martingale estimating functions is generalised to diffusions with finite-activity jumps, when the sampling frequency and terminal sampling time go to infinity. Rate-optimality and efficiency are of particular concern. Under mild assumptions, it is shown that estimators of drift, diffusion, and jump parameters are consistent and asymptotically normal, as well as rate-optimal for the drift and jump parameters. Additional conditions are derived, which ensure rate-optimality for the diffusion parameter as well as efficiency for all parameters. The findings indicate a potentially fruitful direction for the further development of estimation for jump–diffusions.     

那些年,北洋水利那些事儿 1)

本文基于部分历史史实,对北洋大学(今天津大学)水利系的发展进行了简要的梳理,并扼要地回顾了那些年,北洋大学水利那些事儿、那些人。重点从北洋大学-天津大学水利学科、水利系的历史延续及其在中国水利高等教育中的地位、中国第一水工试验所及 其发展过程、天津大学水利馆及知名教授和杰出校友的相关故事出发,以期较为全面地展示北洋大学-天津大学水利系125年的历 史传承和现代化发展成就,激励新一代天大水利人,续写北洋雄风,并深刻缅怀余元君等已故校友。     

南昌市昌东地区鸟类多样性初步调查

2006年7月至2007年9月,对南昌市昌东地区鸟类多样性进行了初步调查,共记录鸟类48种。其中。留鸟26种,冬候鸟11种,夏候鸟8种,旅鸟3种。在鸟类区系类型上,东洋界鸟类22种,古北界鸟类12种。广布种13种,不确定种1种,结果表明区系类型有东洋界和古北界混杂的现象。校园鸟类仅18种,农田最多。为31种,村庄和湿地分别为25和14种。这种差异主要根源于不同生境的微生境多样性的差异。     

群体多目标规划联合加权解的稳定性

对于群体多目标规划问题,得到了在决策变量扰动下联合加权解的稳定性结果,证明了当扰动变量形成了Baire空间时,群体多目标联合加权解是稳定的。     

Excess enthalpies and excess volumes of 1-nitropropane +, and 2-nitro-propane +, each of several non-polar liquids

Excess molar enthalpies H_m^E and excess molar volumes V_m^E have been measured for xC₃H₇NO₂ + (1 ? x)c-C₆H₁₂ at 298.15 and 318.15 K; +(1 ? x)CCl₄ at 298.15 and 318.15 K; +(1 ? x)C₆H₆ at 298.15 and 318.15 K; +(1 ? x)C₆H₁₄ (V_m^E only) at 298.15 K; +(1 ? x)p-C₆H₄(CH₃)₂ at 298.15 K; and for xCH₃CH(NO₂)CH₃ + (1 ? x)c-C₆H₁₂ at 298.15 and 318.15 K; +(1 ? x)CCl₄ at 298.15 and 318.15 K; +(1 ? x)C₆H₆ at 298.15 K; +(1 ? x)C₆H₁₄ at 298.15 K; +(1 ? x)(CH₃)₂CHCH(CH₃)₂ for H_m^E at 318.15 K and for V_m^E at 298.15 K; and +(1 ? x)C₁₆H₃₄ at 298.15 K. The H_m^E′s were determined with an isothermal dilution calorimeter and the V_m^E′s with a continuous-dilution dilatometer. Particular attention was paid to the region dilute in nitroalkane. In general H_m^E is large and positive for (a nitropropane + an alkane), less positive for (a nitropropane + tetrachloromethane), and small for (a nitropropane + benzene) and for (a nitropropane + 1,4-dimethylbenzene). The mixture with hexadecane shows phase separation. V_m^E is large and positive for (1-nitropropane + cyclohexane), less positive for (1-nitropropane + hexane), and S-shaped for (1-nitropropane + tetrachloromethane) with negative values in the 1-nitropropane-rich region. For (1-nitropropane + benzene) and for (1-nitropropane + 1,4-dimethylbenzene) V_m^E is negative. For mixtures with 2-nitropropane the results are similar except that for benzene V_m^E is S-shaped with positive values in the 2-nitropropane-rich region.     

Reactions of hydroxyl radicals with polystyrene

The reaction of polystyrene with hydroxyl radicals, generated by the photolysis (λ > 300 nm) of H₂O₂, has been studied at 25° in dichloromethane solution, both under vacuum conditions and in presence of O₂. Spectroscopic analyses suggest the presence of phenols and hydroxymucondialdehydes (when O₂ is present) among the reaction products, indicating that OH addition occurs at the phenyl groups of the polymer. By comparison with initiated oxidation reactions under the same conditions, it is concluded that the OH radicals undergo mainly addition reactions. A mechanism has been produced to account for the products. The significance of OH addition reactions in the oxidation of polystyrene is considered, the OH radicals being produced by hydroperoxide decomposition during oxidation, and the products having been previously identified as containing mucondialdehydes.     

The 9-barbaralyl cation, 1,4-bishomotropylium ion and some related C9H9 carbocations : Electronic structures, stability and reactivity

The electronic structures of the 9-barbaralyl cation(1), the 1,4-bishomotropylium ion (5) and some related C₉H₉⁺ isomers have been studied byab initio STO-3G calculations. The stability of the cyclopropylcarbinyl cation 1 and the homoaromatic ion 5 as compared with their allylic counterparts is explained in terms of delocalization and MO interactions between molecular fragments. Both the symmetry of, and the distance between, molecular fragments are of importance for the electronic structure, and even symmetry-allowed interactions are negligible in the absence of favourable geometrical distortions. The non-classical ion 3 with D_3h symmetry presents special problems where other factors, such as strain, are important for the total energy. A choice between proposed mechanisms for the degenerate rearrangements of 1 can now be made with confidence.     

A new class of flavonoids bearing macrocyclic polyethers by stereoselective photochemical cycloaddition reaction

A new class of flavonoids bearing cyclic polyethers involving a phenyl ring was conveniently provided by the intramolecular photochemical dimerization of 2-chromonecarboxylic esters. Irradiation of 2-chromonecarboxylate with a polyether tethered at both ends promoted intramolecular [2 + 2] cyclobutane formation leading to 14- to 27-membered cyclic polyethers. The efficiency depended on the substituted position of the phenyl ring, with ortho- and meta-substituted derivatives giving cycloadducts in good chemical yields and quantum efficiencies, whereas the para-derivatives were inert toward photolysis. X-ray crystallographic analysis revealed that the stereochemistry of the macrocyclic cycloadducts exhibited C₂-symmetry.     

Multicomponent reaction of conjugated enynones with malononitrile and sodium alkoxides: Complex reaction mechanism of the formation of pyridine derivatives

Reaction of conjugated enynones,1,5-diarylpent-2-en-4-yn-1-ones, with malononitrile and sodium alkoxides in the corresponding alcohols at room temperature for 3–23 h results in the formation of two types of compounds (E)-/(Z)-6-aryl-4-(2-arylethenyl)-2-alkoxypyridine-3-carbonitriles (substituted nicotinonitriles), as the major reaction products in yields up to ca. 40–80%, and 6-aryl-4-arylethynyl-2-alkoxypyridines, as the minor reaction products in yields of 5–17%. Plausible mechanism of this complex and multistep reaction is discussed. The obtained pyridines possess fluorescent properties.     

Calculation of the spectral distribution of absorption coefficients in vibrational spectra of complicated molecules,polymers and molecular crystals

The interpretation of vibrational spectra of complicated systems is necessary for the subsequent use of these spectra in the analysis of the structure and physical properties of complicated molecules, polymers and molecular crystals.This interpretation is accomplished with the aid of various methods including calculations of frequencies and in certain cases use of the intensities of absorption bands.