It has been proved that arbitrarily high-energy collision between two particles can occur near the horizon of an extremal Kerr black hole as long as the energy $E$ and angular momentum $L$ of one particle satisfies a critical relation, which is called the BSW mechanism. Previous researchers mainly concentrate on geodesic motion of particles. In this paper, we will take spinning particle which won't move along a timelike geodesic into our consideration, hence, another parameter $s$ describing the particle's spin angular momentum was introduced. By employing the Mathisson-Papapetrou-Dixon equation describing the movement of spinning particle, we will explore whether a Kerr-Sen black hole which is slightly different from Kerr black hole can be used to accelerate a spinning particle to arbitrarily high energy. We found that when one of the two colliding particles satisfies a critical relation between the energy $E$ and the total angular momentum $J$, or has a critical spinning angular momentum $s_c$, a divergence of the center-of-mass energy $E_{cm}$ will be obtained.
Based on the existing core and logging data, as well as previous research achievements, various experimental data were obtained by means of thin section, casting thin section, scanning electron microscopy, X-ray diffraction analyses, and cathodoluminescence. These data were used for the purposes of examining the features, diagenetic characteristics, and diagenetic evolution sequences of the Upper Paleozoic reservoirs of the Dongpu Depression, and analyzing the main controlling factors. The research results showed that the reservoir lithology was mainly subarkose, sublitharenite, feldspathic litharenite, and lithic arkose. The reservoir was generally characterized by ultra-low porosity and ultra-low permeability, with low porosity and low permeability in some areas. The pore types mainly include primary intergranular residual pores, dissolution pores, intercrystalline micropores, and microfractures. The pore throats are small and the throat channels are poorly sorted. The diagenetic processes mainly include compaction, pressure dissolution, cementation, metasomatism, and dissolution features of the research area. The diagenetic stages were determined to be mainly the middle diagenetic stages (Stage A and Stage B). The delta distributary channel and distributary bay of the Upper and Lower Shihezi Formation, along with the river channel sub-facies of the Shiqianfeng Formation, were considered to be the strata with good reservoir conditions. Moreover, the sand grains are dominated by medium-to-good sorting properties, sub-roundness and sub-angular, which provided a good spatial basis for the development of the primary pores. The calcite and kaolinite in the interstitial materials were corroded, which played a constructive role in the generation of the secondary pores. The results of the compaction, pressure dissolution, and cementation analyses indicate destructive diagenesis, which potentially reduced the porosity and permeability values. However, the dissolution, metasomatism, and chlorite lining cementation indicate improved diagenesis, which potentially increased the porosity and permeability values.
The complex geological environment about arch dam site of Wanjiakouzi hydropower station influences the normal operation state and stability of arch dam.Three-dimensional numerical model based geological information is established.Three-dimensional elastic-plastic finite element method is applied to analyze stress and deformation change of dam body and foundation rock.The results show that the reinforcement measure improves the stress and displacement distribution conditions of dam body and dam foundation effectively and raises the arch dam stability.
In flexural strength design of normal-strength concrete (NSC) beams, it is commonly accepted that the distribution of concrete stress within the compression zone can be reasonably represented by an equivalent rectangular stress block. The stress block it governed by two parameters, which are normally denoted by ${\alpha}$ and ${\beta}$ to stipulate the width and depth of the stress block. Currently in most of the reinforced concrete (RC) design codes, ${\alpha}$ and ${\beta}$ are usually taken as 0.85 and 0.80 respectively for NSC. Nonetheless, in an experimental study conducted earlier by the authors on NSC columns, it was found that ${\alpha}$ increases significantly with strain gradient, which means that larger concrete stress can be developed in flexure. Consequently, less tension steel will be required for a given design flexural strength, which improves the ductility performance. In this study, the authors' previously proposed strain-gradient-dependent concrete stress block will be adopted to produce a series of design charts showing the maximum design limits of flexural strength and ductility of singly-and doubly-NSC beams. Through the design charts, it can be verified that the consideration of strain gradient effect can improve significantly the flexural strength and ductility design limits of NSC beams.
Based on the extensive research and analysis of actual condition of top culvert of high embankment, a calculation theory for the earth pressure of top culvert was presented. The theory could optimize the structure design for culverts, and reduce the waste of resource. First, based on the simplified assumption of the stress of soil on the top culvert and the analysis of single unit of the load on the top culvert, the calculation formula of earth pressure on different position of top culvert was presented by theoretical derivation. Then, to verified the results by using scaled test model and ABAQUS finite element software. Through the comparison with the traditional calculation theory and finite element simulation, we could prove that the calculation theory is more tallies with the actual situation of the earth pressure on the top culvert.
As an alternative to traditional verbal counselling, expressive arts therapy has been shown to be an effective method of mental health care, particularly when dealing with stressful public interactions, such as those associated with COVID-19. However, few studies have been conducted to determine the efficacy of expressive arts therapy on the resilience of psychologically exposed university students during COVID-19. Furthermore, since network analysis appears to be a popular approach in psychological research, it has not been used in recent intervention studies for resilience. As a result, the current study utilized a network analysis approach to determine the efficacy of expressive arts therapy on the resilience of university students during the COVID-19 pandemic. A total of 263 students in a comprehensive university in China were selected for the therapy group between March and November 2021. In a pre-post design, students’ resilience was assessed using the Resiliency Scale for University Students (RSUS). The extended Bayesian information criteria (EBIC) and graphical LASSO were used to estimate and define paired resilience networks, and the strength, betweenness, and closeness indices were utilized to determine the centrality of the six facets of resilience. Additionally, we verified the stability and accuracy. It was discovered that significant differences appeared between the paired networks before and after expressive arts therapy. Facets of self-efficacy, self-acceptance and problem-solving in resilience were notably improved after the therapy, with the variable of emotional stability sustained at the mean level. Meanwhile, the network analysis has highlighted the central variable of self-efficacy in the pre-intervention and support from friends in the post-intervention. The connectivity among the components of problem solving, support from friends, and support from family was enhanced, with support from friends playing the role of hub nod in the following network. By utilizing a network analytic approach, expressive arts therapy can be more targeted in intervening in resilience mechanisms. As a proxy for efficacious problem-solving, intervention should be calibrated to the cultivation of social support networks, especially in the support from friends.
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