RESUMEN
The class G oil well cement is a type of special cement that can be subjected to a high temperature formation environment. It was found that the class G cement tail slurry with a low polycarboxylic retarder dosage (usually ≤1% by weight of cement) was more prone to cause the abnormal gelation phenomenon (AGP) than the lead slurry with a high retarder dosage at a high temperature (usually when T ≥ 120 °C). This study aimed at the occurrence mechanism of this unfavorable phenomenon that seriously endangers the cementing security. Results showed that the abnormal gelatinous region underwent premature hydration; namely, the calcium hydroxide and calcium silicate hydrate (C-S-H) content were all higher than the nongelatinous region, while the copolymer content was the opposite. Correspondingly, the theory of "premature hydration and crystal nucleation" was proposed to explain the abnormal gelation mechanism of a cementing tail slurry with an insufficient retarder dosage. Furthermore, a novel functionalized copolymer retarder "PAIANS" was synthesized to alleviate the AGP.
RESUMEN
Cementitious materials inevitably develop cracks, posing a serious threat to the long-term security of infrastructure, especially in the complex underground environment of cementing engineering. Microcapsules are facing the problem of encapsulated structure damage during the mixing and breaking difficultly during self-healing when applied in cementitious materials, resulting in the decline of self-healing efficiency. Herein, the calcium alginate water-adaptive microcapsules (CaAlg-NS/E-51) were prepared via an O/W/O emulsion, and the water adaptability of the shell was applied to achieve a rapid brittle-ductile transition by absorbing water. The water adaptability of the microcapsule is conducive to resisting shear stress during stirring due to the decreased elastic modulus and the increased ductility of the shell when it absorbs water. Meanwhile, the water-bearing shell loses water and becomes brittle during dry curing, making it prone to fracture when self-healing. In the self-healing measurement, the self-healing efficiency of cementitious specimens with microcapsules absorbing water for 10 min improved by 234.9 and 60.0% at 1 and 7 days, respectively, compared with those containing dry microcapsules, owing to the water adaptability of the shell.
RESUMEN
Perfluorinated isobutyronitrile (C4F7N) is favored in electrical engineering because it is an environmentally friendly gas-insulating medium with a low greenhouse effect. Unfortunately, under the influence of electricity and over-heating, its decomposition results in the deterioration of its insulating properties, which potentially leads to partial discharge or even gas breakdown. In this paper, the adsorption behavior of C4F7N gas and its toxic decomposition product, acetonitrile (C2N2), on MoS2 surfaces doped with small copper clusters was investigated by calculating the adsorption energy and density of states, etc. The effects of multiple initial adsorption positions as well as externally applied electric fields were also taken into account. The results depict that the maximum adsorption energy of C4F7N on the Cuγ (γ = 1-3)-MoS2 surface gradually decreases with the increase in γ. The Cu3-modified MoS2 is most suitable for use as a resistive-based gas-sensitive sensor substrate. This paper provides the theoretical foundation for the maintenance of future power equipment with environmentally friendly insulating gas.
RESUMEN
The aim of the current study was to investigate the personality characteristics and developmental characteristics of primary school students' personality types in a cross-sectional sample of 10,366 Chinese children. The Personality Inventory for Primary School Student was used to evaluate primary school students' personality. Latent profile analysis (LPA) was used to classify primary school students' personality types. One-way ANOVA was used to explore the personality characteristics of personality types, and Chi-square tests were used to investigate grade and gender differences of primary school students' personality types. Results showed that the primary school students could be divided into three personality types: the resilient, the overcontrolled, and the undercontrolled. Resilients had the highest scores, and undercontrollers had the lowest scores on all of five personality dimensions (intelligence, conscientiousness, extraversion, agreeableness, and emotional stability). The overcontrollers' scores on personality were between the other two types, with lower emotional stability. As the grade level increased, the proportion of undercontrolled students in primary schools generally showed an upward trend and reached the maximum in grade 5. The proportion of resilient students in primary schools generally showed a downward trend. The proportion of resilient students was highest in grade 2 and lowest in grade 5. Girls were significantly more likely than boys to be resilient personality types, while boys were significantly more likely than girls to be undercontrolled personality types. The overcontrolled personality type did not show significant gender differences. Because of the undesirable internalizing problems related to overcontrollers and the externalizing problems related to undercontrollers, our results have implications for Chinese schools, families, and society in general.
RESUMEN
Three personality types (resilient, overcontrolled, and undercontrolled) have been repeatedly verified across different languages and cultures, different personality models, and different stages of development. Undercontrollers are socially maladapted types with high impulsivity and low self-control. Research shows they are at risk for externalizing problems, such as aggressiveness, impulsivity, and antisocial behavior. The aim of this study was to develop an intervention to reduce externalizing problems of undercontrolled personality types in primary school students. Participants were 69 undercontrolled primary school students from two primary schools in North China. The experimental group underwent 14 weeks of systematic experiential mental health activities, while the control group performed typical daily classroom activities. Personality and externalizing problem behaviors were measured before the intervention, at the end of the intervention, and 4 months post-intervention. The results showed that the intervention significantly reduced the level of externalizing problems of undercontrolled primary school students. The effects of the intervention were maintained at the 4-month follow-up. This study provides some reference and suggestions on how to intervene in the externalizing problem behaviors of undercontrolled primary school students.
RESUMEN
Additives in the petroleum industry have helped form an efficient system in the past few decades. Nowadays, the development of oil and gas has been facing more adverse conditions, and smart response microcapsules with the abilities of self-healing, and delayed and targeted release are introduced to eliminate obstacles for further exploration in the petroleum industry. However, limited information is available, only that of field measurement data, and not mechanism theory and structural innovation data. Thus we propose that the basic type, preparation, as well as mechanism of microcapsules partly depend on other mature fields. In this review, we explore the latest advancements in evaluating microcapsules, such as X-ray computed tomography (XCT), simulation, and modeling. Finally, some novel microencapsulated additives with unparalleled advantages, such as flexibility, efficiency, and energy-conservation are described.
