Leak-off behavior and water shut-off performance of a polymer/chromium(Cr^(3+)) gel in fractured media

During gel treatments for fractures, the leak-off behavior of gelant has a great effect on the water shut-off performance of gel. Experiments were carried out using a polymer/chromium(Cr^(3+)) gel system to explore the leak-off behavior and the water shut-off performance of gel in fractured media. Results of the gelant leak-off study show that the gelant leak-off from fracture into matrix contributes to the formation of the gelant leak-off layer during the gelant injection. Moreover, because of the gradual formation of the gelant leak-off layer along fracture, the initial leak-off ratio of gelant is relatively high, but it declines and finally levels off with the increase of the injection volume. The polymer concentration of gelant has a great effect on the chromium output in fluids produced from fractures. With the increase of the polymer concentration, the chromium concentration first decreases and then increases, and the leak-off depth of gelant into matrix is gradually reduced. Results of the water shut-off study present that the decrease of the chromium concentration inside the fracture greatly reduces the water shut-off performance after the gel formation. Therefore, because of the relatively high degree of chromium leak-off, enough injection volume of gelant is essential to ensure the sufficient chromium concentration inside the fracture and to further achieve a favorable water shut-off performance. On the premise of gel strength assurance inside the fracture, the water shut-off performance of gel gradually declines with the extension of the distance from the fracture inlet, and different leak-off degrees of gelant along the fracture are responsible for this phenomenon. Therefore, a proper degree of gelant leak-off contributes to enhancing the water shut-off performance of gel for fractures.

Trends and Prospects of Stem Cell Research in China

Great progresses have been made in fundamental and clinical stem cell research in China in recent years. The official policy on stem cells, which was announced in 2015, seems as the spring of stem cell therapy in China. However, the regulation, governance, and management of clinical expectations are still challenging. This review summarized the current stem cell research and development in the field, as well as its rapidly evolving commercial, regulatory and ethical environment in China. As expected, the prospects of stem cells in China look prospective.

Text-mining analysis using national R&D project data of South Korea to investigate innovation in graphene environment technology

This study investigates the possibilities offered by the development of graphene environment technology that can contribute to new and effective approaches for the transition to an ecologically benign ecosystem.To analyze the research and development progress in graphene environment technology,graphene environment technology research trends of South Korea for the years 2009e2020 are investigated by acquiring information pertaining to national research and development projects related to graphene environment technology from the National Science and Technology Information Service.Both structured and unstructured data are analyzed using diverse text-mining methods,such as keyword frequency analysis,association rule mining,and topic modelling.The results indicate that graphene research in South Korea is focused primarily on graphene use in batteries and energy-storage devices,such as solar cells,fuel cells,and secondary batteries.This study can help understand the manner by which the South Korean government has been investing in the research and development of graphene environment technology;additionally,it discusses the future applications and prospects of graphene for the next decade.

Combined effects of physical activity and calcium on bone health in children and adolescents:a systematic review of randomized controlled trials

Background A better understanding of the role of exercise and nutrition in bone health is significant for preventing osteoporosis.The aim of this review was to assess the combined effects of physical activity and calcium intake on improving bone mineral density in children and adolescents.Methods A search of electronic databases(MedLine,ISI Web of Science,Science Direct)and the literature references were performed.Randomized controlled trials published between 1997 and 2017,evaluating the effect of both physical activity and calcium intake intervention on bone mineral density or bone mineral content among children aged 3–18 years were selected.The Improved Jadad Rating Scale was used to assess the methodological quality of the included studies.Study characteristics were summarized in accordance with the review’s PICO criteria.Changes in bone mineral content were detected at several different bone sites.Results A total of nine studies involving 908 participants were included in this review.The combined intervention of physical activity and calcium increased bone mineral in children and adolescents,especially when baseline calcium intake level was low and among participants on the stage of early puberty.Conclusions Regular physical activity combined with high level of calcium intake is beneficial for bone health in young population.Further research is needed to evaluate the dose–response associations and long-term effects of the interaction between physical activity and calcium intake.

Using Computational Intelligence Algorithms to Solve the Coalition Structure Generation Problem in Coalitional Skill Games

Coalitional skill games （CSGs） are a simple model of cooperation in an uncertain environment where each agent has a set of skills that are required to accomplish a variety of tasks and each task requires a set of skills to be completed, but each skill is very hard to be quantified and can only be qualitatively expressed. Thus far, many computational questions surrounding CSGs have been studied. However, to the best of our knowledge, the coalition structure generation problem （CSGP）, as a central issue of CSGs, is extremely challenging and has not been well solved. To this end, two different computational intelligence algorithms are herein evaluated： binary particle swarm optimization （BPSO） and binary differential evolution （BDE）. In particular, we develop the two stochastic search algorithms with two-dimensional binary encoding and corresponding heuristic for individual repairs. After that, we discuss some fundamental properties of the proposed heuristic. Finally, we compare the improved BPSO and BDE with the state-of-the-art algorithms for solving CSGP in CSGs. The experimental results show that our algorithms can find the same near optimal solutions with the existing approaches but take extremely short time, especially under the large problem size.