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BackgroundNuclear power simulation technology has been widely applied in areas such as reactor design, safety analysis, independent safety evaluation, accident mitigation measures, design and optimization of control and protection system, verification of advanced main control room design, and operator training. This technology has effectively improved the safety and economy of nuclear power plants.PurposeThis study aims to develop a real-time modeling and simulation platform for a liquid-fueled molten salt reactor (LF-MSR) based on the open-source and open architecture of the experimental physics and industrial control system (EPICS).MethodsFirst, the real-time interaction function of the LF-MSR system code, RELAP5-TMSR, was improved, and the control and protection system and human-machine interaction interface were extended. Then, the ThorTypography simulation platform was preliminarily developed for LF-MSR by integrating the above three main functional modules. Finally, ThorTypography was validated using the pump start-up experiment, pump coast-down experiment, natural circulation experiment, and reactivity insertion experiment from the Molten Salt Reactor Experiment (MSRE) as the benchmark.ResultsThe test results of ThorTypography are consistent with the calculation results of RELAP5-TMSR and are in good agreement with the MSRE data. Moreover, the total simulation time is consistent with the total physical problem time.ConclusionsThorTypography is suitable for real-time modeling and simulation of LF-MSR systems and can provide effective support for LF-MSR design, operation, and safety analysis.

In order to reduce the failures during cigarette group forming, the cigarette pusher in YB48 hard packer was redesigned. Enlightened by the structural characteristics of plants with hollow stalks, the shape of the spacer plate of the cigarette plunger was optimized and the working surface of the cigarette guide block was modified accordingly. On the basis of ANSYS platform, the simulation analysis of the cigarette plunger before and after modification was conducted with finite element method. The results showed that the static and dynamic specific stiffness efficiencies of the modified cigarette plunger increased by 65.62% and 36.01% respectively, and its comprehensive mechanical property was promoted significantly. The modified cigarette plunger was tested on two YB48 hard packers in Lanzhou Cigarette Factory, the results indicated that the failures of cigarette pusher reduced by 37.17%, and the machine's downtime decreased by 38.34%. This technology provides a support for improving the efficiency of ultra-high speed packaging equipment. [ABSTRACT FROM AUTHOR]

Evapotranspiration is the main way of soil water depletion in field, and soil evaporation is an important part of evapotranspiration, and it may account for 32%-50% of the total evapotranspiration during the whole crop growth period. Soil evaporation does little effect on the formation of crop biomass and yield, so reducing soil evaporation is important for improving water use efficiency and agricultural water saving management. In recent years, straw mulching has been used widely due to its capability of improving soil structure, increasing soil organic matter, reducing soil evaporation and maintaining soil water content. Mulching affects exchange of energy and heat between soil surface and free air, so the mechanism for soil evaporation under mulching condition may be different from that without mulching. Considering the fast development of straw mulching, therefore modeling soil evaporation under straw mulching is of important for making agricultural water management. In this paper, the factors (soil water content and mulching amount) that affect soil evaporation had been analyzed, the values of mulching resistance were calculated, the equations for calculating resistance of mulching and the resistances of soil evaporation and soil evaporation under straw mulching had been established, the parameters for the equation had been determined. The experiment was carried out from late July to middle August in 2010 and from middle July to middle August in 2011, respectively. The undisturbed soil with winter wheat plants was prepared and put into plastic buckets when winter wheat was maturity, two main treatments (stubble and stubble+mulch treatments) were set up, there were five sub-treatments for each of the two main treatments. The stubble heights for stubble treatments were 0, 5, 15, 25, 35cm. Stubble heights were 0, 5, 15, 25, 35 cm with mulching amounts of 0.47, 0.43, 0.348, 0.267, 0.187 kg/m2 in stubble+mulch treatment, respectively. The total biomass (stubble biomass) for each stubble treatment was 0, 0.04, 0.122, 0.203, 0.283 kg/m2, respectively; the total biomass (stubble biomass and mulching amount) in each stubble+mulch treatment was 0.47 kg/m2. During the prepared period, water was applied to the soil until all the soil in the plastic bucket was saturated, and then the excessive water was discharged out off plastic bucket through small hole at the bottom of plastic bucket to make sure soil water content was about field capacity at the beginning of the experiment. The soil evaporation and soil temperature were measured daily and soil water content in 0-2 cm depth was measured every 2 ~ 5 days according to the soil evaporation. Meteorological data, including relative humidity, hourly mean air temperature, and wind speed were measured with an automatic weather station. Results showed that the relative soil evaporation (the ratio of soil evaporation to water evaporation from 20 cm diameter pan) kept relatively stable when soil water content was higher than 0.23 cm3/cm3 (60% field capacity), the ratio declined linear with the decreasing of soil water content when soil water content was higher than 0.05 cm3/cm3 (wilting point) and less than 0.23 cm3/cm3. Mulching affected soil evaporation, reducing stubble height and increasing mulching amount could reduce soil evaporation when the total biomass was the same. The total amount of soil evaporation during experiment period reduced by 8%-51% under stubble+mulch treatment with mulching amount of 0.348-0.47 kg/m2 compared with stubble treatment when stubble height was 0-15 cm. Mulching resistance was 158-600 s/m in this study and it was exponentially increasing with the mulching amount, and the resistance of soil layer decreased linearly with the soil water content increasing when soil water was less than 0.23 cm3/cm3 and higher than 0. 05 cm3/cm3. The validation processes showed that the developed method and related parameters (mulching resistance and the resistance of soil layer) performed well for modeling soil evaporation under mulching condition. [ABSTRACT FROM AUTHOR]

Existing neuroregulatory techniques can achieve precise stimulation of the whole brain or cortex, but high-focus deep brain stimulation has been a technical bottleneck in this field. In this paper, based on the theory of negative permeability emerged in recent years, a simulation model of magnetic replicator is established to study the distribution of the induced electric field in the deep brain and explore the possibility of deep focusing, which is compared with the traditional magnetic stimulation method. Simulation results show that a single magnetic replicator realized remote magnetic source. Under the condition of the same position and compared with the traditional method of stimulating, the former generated smaller induced electric field which sharply reduced with distance. By superposition of the magnetic field replicator, the induced electric field intensity could be increased and the focus could be improved, reducing the number of peripheral wires while guaranteeing good focus. The magnetic replicator model established in this paper provides a new idea for precise deep brain stimulation, which can be combined with neuroregulatory techniques in the future to lay a foundation for clinical application.

Polyhydroxyalkanoates (PHAs) are polymers obtained by esterification of hydroxy fatty acid monomers. Due to similar mechanical characteristics of traditional petroleum-based plastics, 100% biodegradability and biocompatibility, PHAs are considered to be one of the most potential green materials. However, the application and promotion of PHAs as a green and environmentally friendly material are difficult because of the high production costs. This article focuses on the current methods to reduce production cost of PHAs effectively, such as cell morphology regulation, metabolic pathway construction, economic carbon source utilization and open fermentation technology development. Despite most research results are still limited in laboratory, the research methods and directions provide theoretical guidance for the industrial production of economic PHAs.

Chromosomal integration enables stable phenotype and therefore has become an important strategy for breeding of industrial Saccharomyces cerevisiae strains. pAUR135 is a plasmid that enables recycling use of antibiotic selection marker, and once attached with designated homologous sequences, integration vector for stable expression can be constructed. Development of S. cerevisiae strains by metabolic engineering normally demands overexpression of multiple genes, and employing pAUR135 plasmid, it is possible to construct S. cerevisiae strains by combinational integration of multiple genes in multiple sites, which results in different ratios of expressions of these genes. Xylose utilization pathway was taken as an example, with three pAUR135-based plasmids carrying three xylose assimilation genes constructed in this study. The three genes were sequentially integrated on the chromosome of S. cerevisiae by combinational integration. Xylose utilization rate was improved 24.4%-35.5% in the combinational integration strain comparing with that of the control strain with all the three genes integrated in one location. Strain improvement achieved by combinational integration is a novel method to manipulate multiple genes for genetic engineering of S. cerevisiae, and the recombinant strains are free of foreign sequences and selection markers. In addition, stable phenotype can be maintained, which is important for breeding of industrial strains. Therefore, combinational integration employing pAUR135 is a novel method for metabolic engineering of industrial S. cerevisiae strains.