The electrochemical behavior of a system with a limited number of molecules

In this paper, based on Einstein relationship between diffusion and random walk, the electrochemical behavior of a system with a limited number of molecules was simulated and explored theoretically. The transition of the current vs time responses from discrete to continuous was clearly obtained as the number of redox molecules increased from 10 to 10(6).

Diffusion-limited kinetics modeling of one-step polyimide formation

A diffusion-limited kinetic model was developed to describe the imidization of one-step polythioetherimide formation based on an endgroup diffusion model. The changes of conversion and viscosity during the imidization were monitored with thermogravimetric analysis and dynamic stress rheometry, respectively. It was observed that the imidization rate began to decelerate after a fast early stage, whereas the viscosity in the system increased dramatically after a period of low value. Amic acid and imide formations concurrently take place in the one-step polyimide formation, but the formation of amic acid is much slower than that of imide and is the rate-limiting step of imidization. When a second-order kinetic model was used to describe the imidization, the effect of viscosity on the diffusion resistance of reactive groups needed to be included. In order to predict the change of viscosity during the imidization, the Lipshitz-Macosko model was modified and introduced into the diffusion-limited kinetic model by the Stokes-Einstein equation. The comparison of the modeled results with experimental data indicated that the diffusion-limited kinetic model and the modified Lipshitz-Macosko model were able to efficiently predict the changes of conversion and viscosity with temperature and time during the one-step polythioetherimide formation. (C) 2001 John Wiley & Sons, Inc.

Determination of electron mobility in a blue-emitting alternating block copolymer by space-charge-limited current measurements

In this communication we analyse current versus voltage data obtained using one carrier injection at metal/polymer/metal structures, The used polymer is a soluble blue-emitting alternating block copolymer, Our experimental results demonstrate that the electron current is limited by a large amount of traps with exponential energy distribution in the copolymer. The electron ;mobility of 5.1 x 10(-10) cm(2)/V s is directly determined by space-charge-limited current measurements. The electron mobility is at least three orders of magnitude smaller than that for holes in the copolymer. (C) 1999 Elsevier Science Ltd. All rights reserved.

Typhoon effects on DOC dynamics in a phosphate-limited reservoir

To explore typhoon effects on dissolved organic carbon (DOC) dynamics, field investigations (tributary and dam site) and laboratory experiments (bioassay and DOC consumption) were conducted in a subtropical reservoir. A tributary survey indicated that after typhoon disruption, upstream areas were the sources of phosphate (P) but not DOC for the dam site located downstream. Bioassay experiments verified P-limitation on bacteria and phytoplankton during summer stratification, and bacteria showed a faster response than algae to added P. Experiments indicated that DOC consumption was determined by the availability of P. The 4 yr typhoon period (June-September) data of the dam site denoted that DOC concentration (27 to 270 mu M C) and its rate of change (-13 to 24 mu M C d(-1)) varied more dramatically in the weak (2006 and 2007) than in the strong (2004 and 2005) typhoon years. The negative correlation of DOC with the ratio of bacterial production (BP) to primary production (PP) in the euphotic zone (0 to 10 m) signified the interactive effects of auto- and heterotrophic processes on DOC variation. In the aphotic zone, the variation of DOC could be ascribed to the change of BP, which showed a positive correlation with P concentrations. This study documents that DOC concentration in the studied system varied at multiple time scales. Such variation can be explained by the decoupling between BP and PP, which is believed to be a function of the limiting nutrient's availability. More importantly, this study suggests that the P supply introduced by strong typhoons might have substantiated a tighter coupling between BP and PP, so that the amplitude of DOC oscillation during the summer period was effectively reduced.

冀东油田南堡滩海地区油气层损害机理与油气层保护方法研究及应用

Study and Application of Damage Mechanism and Protection Method of reservoir in Nanpu Shallow Beach Sea Area is one of the key research projects of Jidong Oilfield Company of PetroChina Company Limited from 2007 to 2008. Located at Nanpu Sag in Huanghua Depression of Bohaiwan Basin, Nanpu Shallow Beach Sea Area with 1000km2 exploration area posseses three sets, shallow Minghuazhen Formation and Guantao Formation of Upper Tertiary, middle-deep Dongying Formation of Lower Tertiary, deep Ordovician, of oil bearing series, according to the achievement of the connecting 3D seismic structure interpretation and the structural geological comprehensive research. Its main reservoir types include Upper Tertiary structural reservoir, Lower Tertiary structural and lithological-structural reservoir, and Ordovician ancient buried hill reservoir. How to protect reservoir, complete well and lift high efficiently is the key to realize high and stable yield of the oil wells during drilling, completing well, testing and repairing well. It is important for reservoir protecting during drilling that directly relate to efficient exploration. Therefore, beginning with basic characteristics and sensitive analysis of reservoir, study of reservoir damage machinism and analysis of reservoir damage potential factor are emphasized when prediction analysis about three-pressure profiles is carried out. The study both of physical and chemical properties and of the strata of the technology of borehole stabilization and reservoir protecting are outstanding. As the conclusions follow: （1）Based on the laboratory experiment about basalt cores, prediction of three- pressure profiles about 30 wells on No.1 and No.2 structure is practiced. The laws of plane pressure distribution are analyzed. （2）According to the analyses about reservoir feature data and about sensitivity evaluation to damage factor in Nanpu oil field, the scheme of reservoir protecting to the sand reservoir of Guantao Formation and the first section of Dongying Formation is put forward. （3）On basis of the analyses on lithological characteristics, mineral compositions, clay minerals, electrical behavior features, physical and chemical properties of basalt of Guantao formation in No.1 and No.2 structure, instability mechanism of basalt sidewall and technical countermeasures are obtained. （4）Aiming at the characteristics of Ordovician dissolution-pore fracture type carbonate reservoir, the scheme of the reservoir protecting to Ordovician is put forward. Creative study of the film forming and sealing and low invasion reservoir protection drilling fluid are successful. In summary, through the study of reservoir heterogeneity and sensitivity, a set of technology and schemes of reservoir protecting is put forward, which is adaptive during drilling the target bed in the research area and establishes the base for efficient exploration. Significant effect has showed in its application in Nanpu oil field.

不同行业的企业形象要素体系的共性与个性

In the early part of this century, with the change from the seller's market to the buyer market, the competition between companies changed from product competition, selling competition to corporate image competition, and companies began to consciously build corporate reputation through fast developed mass media. As a result, a series of methods to build corporate image were created, such as advertising, public relations and corporate identify system(CIS), which ,in turn, promoted the development of the research of corporate image. The factors of corporate image have been the central issue of the corporate image research, for the probe of this issue is of great significance to both the development of corporate image theory and the practice of corporate image building. As far as the literature we have gathered is concerned, the exiting research on this topic either remains at the level of qualitative investigating and induction, or is limited in some particular industry. Therefore. There bean no commonly accepted corporate image theory so far. In the recent years, with the introduction of competition mechanism and the establishment of the company. As subject position in the market, the building of corporate image gas been developed quickly in our country, and the development of practice imperatively requires the guide of scientific theory. On the basis of the analysis and summarization of the research of the predecessors, the present dissertation attempts to do some investigation and research work on the common and individual characteristics of corporate image factors of the companies in different industries in our country. The method of questionnaire survey is used in the present research. The subject sample is gathered on the basis of convenience and feasibility, and at the mean time, some consideration is also given to straticulate randomization principles. The subjects are asked to select one of their most familiar companies, and determine the important of even item in the questionnaire to the selected company(i.e. the importance assessment), and then, determine the grades the selected company gains on every item(i.e. the image assessment). The discriminant analysis of corporate image of different industries. The selected sample is grouped and coded according to the standard of industry classification. The discriminant analysis is done with the selected companies as the sample and the grades of image assessment as the variables. The result indicates that industry variable is an important standard of the classification of corporate image, and the companies in the same industry are more similar in corporate image. The analysis of the common and individual characteristics of corporate image of different industries. Firstly, in every industry, the items are sieved according to the grades of importance assessment, and exploratory factor analysis is done with grades of image assessment on the selected items as the variables. Secondly, the factors drawn from every industry in arranged in order according to their importance. The result indicates that the corporate image of different industries shares some common characteristics, for there exist common factors among different industries. In the mean while, the corporate image of different industries has its individual characteristics, that is, there is some difference in the domain of the factors, and in the order of the factors(including the difference of the principle factor).