[en] We report the photophysical and electroluminescence (EL) properties of two fluorene-based copolymers, poly{[9,9-bis(2-ethylhexyl)fluorene-2,7-diyl]-alt-[6,6'- bis(3-phenylquinoxaline)-2,2'-diyl]} (Qx-PF) and poly{[9,9-bis(2- ethylhexyl)fluorene-2,7-diyl]-alt-[N,N'-diphenyl-N,N'-bis(4-phenyl)-1, 1'-biphenyl-4,4'-diamine]} (TPD-PF). The two copolymers in thin films show blue emission approximately 429-452 nm with relatively narrow bandwidth upon photoexcitation. Electroluminescence has been demonstrated using TPD-PF as the active polymer in the light-emitting electrochemical cell (LEC) with a turn-on voltage at 2.8 V and an EL efficiency of 0.002 cd/A. Due to the improved electron-transporting property, the Qx-PF-based LEC achieves the EL efficiency of 0.07 cd/A, 35 times higher than that of the TPD-PF-based device. Compared to the photoluminescence spectra, EL spectra show enhanced excimer emission, which is primarily related to self-heating of the devices during operation. The main process involved in the decrease of the light intensity during device operation is the electrochemical degradation of the polymer blend

[en] [Objective] The aim was to provide strategies for development of rare earth and control of environmental pollution. [Method] Responses of membrane lipid peroxidation and endogenous hormones of soybean seedlings to UV-B radiation and rare earth were studied through hydroponics in laboratory. [Result] The results showed that under irradiation of UV-B(T1-0.15 W/m2 and T2-0.45 W/m2), chlorophyll and indole-3-acetic acid(IAA) contents firstly decreased during the stress phase (1-5d) and then increased during the restoration phase (6-9d) while contents of malonadialdehyde(MDA) and abscisic acid(ABA) gradually increased during the imposition of UV-B radiation (1-5d) and subsequently decreased during recovery from UV-B stress (6-9d) . With adding of La (Ⅲ) with the concentration of 20mg•L-1, the decline/rise trend of chlorophyll, IAA, MDA and ABA contents was slowed down during the stress period while the rise/decline speed was accelerated during the recovery period. [Conclusion] It suggests that the regulation of La (Ⅲ) on membrane lipid peroxidation and endogenous hormones could increase chlorophyll and IAA contents, improve the metabolism of reactive oxygen species (ROS), inhibit membrane lipid peroxidation, decrease the accumulation amount of ABA and alleviate injury of UV-B radiation to soybean seedlings. Further, the protective potential of La (Ⅲ) was better under low UV-B radiation than under high one

[en] Jiji sub-area is one of the candidates in Beishan area, Gansu province-the preselected area for Chinese high-level radioactive waste repository. 13012 joints data is obtained by comprehensive joint survey method in Jiji quarry. According to the two faults, Jiji quarry is roughly divided into three statistical homogeneities and two region which is influenced by the two faults. Based on the theory of circular sampling window, a computer program is developed and it is used to analyze the diversity of the mean trace length and trace midpoint density in the both side of the faults. So the boundary of the statistical homogeneities is determined and the mean trace length and trace midpoint density of each statistical homogeneity is obtained. The predominant joint cluster of each statistical homogeneity is obtained by rose diagram and equal-area upper hemisphere projection method. The distribution of joint's orientation can be effectively fitted by normal function and the joint dip angles are mostly steep. The joint space of each joint set is calculated and it can be effectively fitted by negative exponential function. According to Suggested Methods for Quantitative Description of Discontinuities in Rock Mass (ISRM,1980), the joint space of each statistical homogeneity is wide spacing. The quantitative parameter of rock mass joint characteristic is obtained and it is essential for further studying the mechanics and seepage characteristics of rock mass. (authors)

[en] Joints are the most ubiquitous and, at the same time, most confusing features of crystalline rocks. Joints and joint network is critical and essential for mechanical and permeability property of rock masses; it may provide the preferential route for groundwater. flow and high-level radioactive nuclide migration. The effect of rock mass joints is paid more and more attention by researchers of rock mechanics, groundwater flow and nuclide migration in recent years. A detailed review is done for the research of rock mass joint simulation and the joint in Beishan area, Gansu province, the preselected area for China's HLW disposal. The theory, method and results for the research of every feature of joint, joint system model and joint in Beishan area, Gansu province are summarized and commented briefly. Finally, some key problem is pointed out which need to be studied emphatically in the research for joint of Beishan area, Gansu province. (authors)

[en] Highlights: • The effect of high temperature on the properties of Beishan granite was studied. • Two types of stress-permeability curve were found for samples after heat treatment. • Thresholds of temperature and heating rate were recognized by multiple tests. • The relationship between AE hits induced by heating and permeability was studied. • Volumetric strain of cracks was applied to analyze the evolution of permeability. - Abstract: Thermal damage in Beishan granite subjected to high temperature treatment (from 100 °C to 800 °C at different heating rates, ranging from 1 to 15 °C/min) is studied in order to assess the thermal effect on physical and mechanical properties. Laboratory tests including acoustic emission (AE) monitoring, ultrasonic velocity and porosity measurements, scanning electron microscope (SEM), tri-axial compression tests with permeability measurement were applied in this study. Two temperature thresholds, 300 °C and 573 °C, are recognized. Physical and mechanical properties of heated granite weaken with the increase of temperature. Especially when the temperature exceeds 573 °C, the weakening becomes more pronounced. Thermally induced cracks in granite are mainly intergranular cracks from 100 °C to 573 °C. However, once the temperature exceeds 573 °C, intra-granular cracks begin to develop due to the phase transition of quartz. Two typical stress-permeability curves of heated granite are observed and their mechanism is analyzed. In addition, the relationship between the number AE hits and initial permeability is discussed. The volumetric strain of cracks is applied to study the permeability evolution during the compressive loading process.

[en] Highlights: • A porosity prediction method is established for calculating the porosity of AIS. • The fractal dimension and compaction index are introduced into porosity calculation. • The graduation equation is recommended to characterize the PSD of AIS. • A device is designed to measure the porosity of insoluble sediment samples. Many insoluble sediments accumulate at cavern bottoms during the construction of salt caverns located in highly insoluble salt formations. Before using the void space for gas storage, knowing the porosity is essential for predicting void volume of insoluble sediments. However, most previous studies have focused on construction and operation of salt caverns, and insoluble sediments have been largely ignored. In this study, a series of laboratory tests, including screening and porosity tests, are conducted to obtain the particle size distribution and porosity of samples obtained by dissolving the nonsalt interlayers of target cavern. The results show that the porosity values of the samples decreases with increasing of fractal dimensions and have no relation to the maximum particle size when the fractal dimension is constant. Based on these results, a porosity prediction method is proposed to calculate the porosity of insoluble sediments combined with fractal and packing theories. In this method, the fractal dimension and the compaction index should be controlled within a reasonable range. The accuracy and reliability of this model was studied by calculating the porosity of insoluble sediments in an actual salt cavern. This study can provide a reference for evaluating the void volume in insoluble sediments.

[en] Highlights: • Operation safety and peak-shaving performance varies with gas production rates. • Selecting gas production rates in terms of safety in cavern, tubing and wellhead. • Thermodynamic parameters during production are modeled mathematically and solved. • Proposed method to design maximum gas production rate and compiled into software. • Verified design method using case application and field data. The maximum gas production rate from salt cavern gas storages is a key parameter affecting its operating safety and peak-shaving performance. However, there is no mature and reliable method for design in it. In this study, the components of a salt cavern gas storage were separated, and many factors affecting the gas production rate are studied in terms of the safety of cavern, tubing and wellhead. These include mechanical stability and volume shrinkage of the cavern, erosion and corrosion of the tubing, generation of hydrate and condensate at the wellhead. Methods are provided for determining the gas production rate to avoid adverse effects, and the thermodynamic parameters during production are modeled mathematically and solved. Finally, an evaluation system for selecting maximum gas production rate from a salt cavern gas storage is proposed and has been compiled into software UGS-GP-design. Applying it to Jintan T5-2 salt cavern gas storage, the feasibility of the proposed method was verified. The study is mostly applicable to natural gas storage, as well as offering theoretical basis and methodological support for salt cavern air and hydrogen storage.

[en] Geological disposal of high-level radioactive waste (HLW) is to dispose HLW in a zone of 500 to 1000 m beneath ground surface and isolate HLW from biosphere for a long period. The key issue of safety assessment is the long term capability of a geological disposal repository for isolating nuclides. It is inevitable to induce Excavation Damage Zone (EDZ) for surrounding rocks during underground engineering construction process, and the induced damage in EDZ will change physical and mechanical properties of surrounding rocks and potentially affect long term safety of the repository. Underground Research Laboratories (URLs) have been built in many countries such as Sweden (ASPO), Canada (URL), Finland (ONKALO), etc. Systematic field tests have been conducted to study the EDZ. In this paper, researches about EDZ built in crystalline rock in URLs are summarized, some key issues in EDZ study are discussed, and the prospect of EDZ studies in our URL is proposed. Overall researches in URL regarding EDZ are comprehensive and may be of great reference value for other underground engineering construction projects such as diversion tunnels and highway tunnels. (authors)

[en] High-level radioactive wastes (HLW) repository is a special deep underground engineering, and in the stages of site selection, designing, constructing ,the stability evaluation, lots of important rock mechanics problems need to be resolved. During the decay of nuclear waste, enormous thermal energy was released and temperature variation caused dynamic distribution of stress and deformation field of surrounding rock of repository. BeiShan region of Gansu province was selected to be the repository field in the future, it is of practical significance to do research on granite in this region. Based on the concept model of HLW repository, this thesis calculates temperature field, stress field and deformation field of HLW repository surrounding rock under the condition of TM coupled with applying the finite difference FLAC"3"D. From this study, thermo-mechanical characteristic of granite is obtained primarily under given canister heat source and given decay law function. And these results show that the reasonable space between disposal hole is 8 m-12 m, and the peak temperature of the canister surface is 130 ℃, the centerline temperature between pits is about 40 ℃ which is maintained for about hundreds of years under given heating output at -500 m depth. (authors)

[en] A one-step colloidal process has been adopted to prepare silver (Ag) and silver sulfide (Ag₂S) nanocrystals, thus avoiding presynthesis of an organometallic precursor and the injection of a toxic phosphine agent. During the reaction, a layered intermediate compound is first formed, which then acts as a precursor, decomposing into the nanocrystals. The composition of the as-obtained products can be controlled by selective cleavage of S–C bonds or Ag–S bonds. Pure Ag₂S nanocrystals can be obtained by directly heating silver acetate (Ag(OAc)) and n-dodecanethiol (DDT) at 200 ° C without any surfactant, and pure Ag nanocrystals can be synthesized successfully if the reaction temperature is reduced to 190 ° C and the amount of DDT is decreased to 1 ml in the presence of a non-coordinating organic solvent (1-octadecene, ODE). Otherwise, the mixture of Ag and Ag₂S is obtained by directly heating Ag(OAc) in DDT by increasing the reaction temperature or in a mixture of DDT and ODE at 200 ° C. The formation mechanism has been discussed in detail in terms of selective S–C and Ag–S bond dissociation due to the nucleophilic attack of DDT and the lower bonding energy of Ag–S. Interestingly, some products can easily self-assemble into two- or three-dimensional (2D or 3D) highly ordered superlattice structures on a copper grid without any additional steps. The excess DDT plays a key role in the superlattice structure due to the bundling and interdigitation of the thiolate molecules adsorbed on the as-obtained nanocrystals. (paper)