Retrieving Domain-Specific Collocations by Co-occurrences and Word Order Constraints

In this paper, we describe a method for automatically retrieving collocations from large text corpora. This method comprises the following stages: (1) extracting strings of characters as units of collocations, and (2) extracting recurrent combinations of strings as collocations. Through this method, various types of domain-specific collocations can be retrieved simultaneously. This method is practical because it uses plain text with no specific-language-dependent information, such as lexical knowledge and parts of speech. Experimental results using English and Japanese text corpora show that the method is equally applicable to both languages.     

长沙市房地产管理局网络系统的设计与实现

介绍了长沙市房地产管理局Ｉｎｔｅｒｎｅｔ网络系统的设计与实现,着重探讨了建立Ｉｎｔｒａｎｅｔ网络系统的过程中应考虑的各种因素,对网络的规划设计和系统软,硬件的选择做了比较详细的介绍。     

Boiling heat transfer of subcooled water in a horizontal rectangular channel: observation of mEB and mEB generation

Forced convection boiling of subcooled water was performed in a horizontal rectangular channel with the heated surface on the bottom. The experiment was conducted for heating surfaces, 10, 20, or 40 mm in length. Microbubble emission boiling (MEB) was observed in subcooled transition boiling and was easy to generate for the shorter heating surfaces. In higher flow velocity of subcooled water, MEB was generated at even lower subcooling. Stormy MEB was observed at both the higher subcooling and the higher flow velocity of water. In the stormy MEB, the heat flux rose rapidly above the critical heat flux with larger acoustic noise and vibration. © 2001 Scripta Technica, Heat Trans Asian Res, 30(5): 426–438, 2001     

Multivariate analysis of heavy metal contamination in urban dusts of Xi'an, Central China

Though there are many studies of heavy metal contaminations of urban dusts in developed countries, little attention has been paid to this kind of study in developing countries, including China. Therefore, a series of investigations were performed to provide heavy metal signatures of urban dusts and to evaluate potential sources in Xi'an, Shaanxi Province. Sixty-five samples of urban dusts were collected in Xi'an. Then Ag, Cr, Cu, Mn, Pb and Zn concentrations were determined by using atomic absorption spectrophotometry, and As, Hg and Sb concentrations by atomic fluorescence spectroscopy. The results indicate that, in comparison with Chinese soil, urban dusts in Xi'an have elevated metal concentrations as a whole, except those of arsenic and manganese. These concentration levels are comparable to those in other studies. Correlation coefficient analysis, principal component analysis (PCA) and cluster analysis (CA) were performed and three main sources with corresponding cluster elements were identified: (1) Ag and Hg have commercial and domestic sources; (2) Cr, Cu, Pb, Sb and Zn are mainly derived from industrial sources, combined with traffic sources as well for Pb and Zn; (3) As and Mn come mainly from soil sources, and As also has an industrial source. Based on PCA and CA analyses, manganese was selected as the reference element, and heavy metal enrichment factors (Efs) were calculated, which in turn further confirms the source identification. Also, Efs give an insight of human influence degree of urban dusts.     

An Extremely Active Pt/Carbon Nano-Tube Catalyst for Selective Oxidation of CO in H2 at Room Temperature

Pt catalyst supported on carbon nano-tube (CNT) was extremely active for the selective oxidation of CO in H₂ at room temperature, which was remarked contrast to the Pt supported on an active carbon (Vulcan carbon) and a graphite powder. Complete oxidation of CO was attained on a 5 wt.% Pt/CNT catalyst (0.8 g) at ca. 40 °C when the O₂/CO ratio in a flow of H₂ (20 mL/min) + CO (3.0 mL/min) + O₂ + N₂ was adjusted to be larger than 0.75 at the total flow rate of 100 mL/min. Specific activity of the Pt/CNT catalyst was explained by efficient provision of reactant molecules diffusing on CNT surface to Pt particles.     

Thermotropic cholesteric mesophases in copoly(γ-n-alkyl l-glutamate)s

Summary Thermotropic cholesteric mesophases were found for three types of -helical copoly(-n-alkyl L-glutamate)s; the combination of the n-alkyl groups was methyl-hexyl, methyl-octyl, and propyl-octyl. Cholesteric colors due to the selective reflection were observed in the temperature range from 110 to 190°C for the films with copolymer compositions of about 50/50 in mol%. These thermotropically mesomorphic copolymers had disordered structures in the molecular packing as inferred from the x-ray diffraction patterns. The cholesteric sense was right-handed, since the negative circular dichroism associated with the cholesteric pitch was observed for all the mesomorphic films. The temperature dependence of the pitch was discussed in comparison with that of lyotropic liquid crystals of these polymers.     

Optically active alternating copolymer and Diels-Alder adduct

Summary Asymmetric induction copolymerization and Diels-Alder reaction were investigated between acrylic monomer and olefin or diolefin with use of an optically active aluminum compound as the complexing agent. In the copolymerization, only benzofuran gave an optically active alternating copolymer, while butadiene and indene gave alternating copolymers but with no optical activity. EtAlCl₂-l-menthol was the most effective complexing agent. However, EtAlCl₂-d-neomenthol was ineffective.On the other hand, Diels-Alder reaction was in general more easily stereocontrolled. For instance, both complexing agents were effective for the synthesis of optically active Diels-Alder adducts with butadiene or cyclopentadiene, perhaps due to the rigid cyclic structure in a transition state of the reaction.     

Phase relations in the VxW1−xO2 system (0.2 ≤ x ≤ 0.75)

The phase relations in the V_xW_1?xO₂ system were studied by vacuum seal technique at 900°C. A new phase was found around composition of x=0.5. It has a slightly distorted rutile-type structure with doubling of the $\text{a}$ and $\text{c}$ parameters of rutile. Phase transition from this phase to rutile-type phase was examined by DTA. Transition temperature increased with decreasing x-value. Enthalpy change for the transition and the variation of monoclinic angle of the phase seemed to have maximum values at composition of x=0.5.