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Zuyun Luo,Xinhua Yang,Heli Ji,Chuanchuan Zhang 한국콘크리트학회 2022 International Journal of Concrete Structures and M Vol.16 No.2
Durability is an important aspect of reliability of concrete structures. In order to establish the carbonation model of polyvinyl alcohol (PVA) fiber concrete including the influences of PVA fiber length and volume content, a series of accelerated carbonation experiments were carried out on the normal concrete specimens and PVA fiber concrete specimens with fiber lengths of 3 mm, 6 mm, 12 mm and 18 mm and fiber volume contents of 0.1%, 0.3%, 0.5%, 0.75%, 1.0% and 1.5%, respectively. The experimental conditions remained at temperature of 20 ℃, humidity of 70%, and carbon dioxide concentration of 20%. It was found that the addition of PVA fibers could improve the carbonation resistance of concrete considerably. Within the investigated range of fiber length and content, the carbonation resistance of concrete is first strengthened and then weakened with increasing PVA fiber length or content. The quadratic carbonation depth prediction model could characterize the influences of PVA fiber length and content better than the linear model. The carbon dioxide diffusion equation was established by introducing a PVA fiber influence factor and its parameters were determined from the carbonation depth prediction model. The carbonation process of PVA fiber concrete under the accelerated carbonation experiment condition was simulated. Both the model and the numerical method were validated by comparison between the experimental and numerical results. Finally, the influences of added PVA fibers on the carbonation life and durability of reinforced concrete components were further studied numerically. The results showed that compared with the normal concrete component, the durability of PVA fiber concrete components is significantly improved.
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Wang Xin,Tang Rongsong,Zhang Heli,Li Fan,Wang Jing,Li Baohua 한국간호과학회 2023 Asian Nursing Research Vol.17 No.2
Purpose: Ankle pump exercises (APE) have been widely used in clinical practice. However, best practices for APE have not been established. Recognize the most effective frequency of APE for improving lower extremity hemodynamics and establish recommendations in clinical practice. Methods: Therefore, a systematic review and network meta-analysis (NMA) was performed according to PRISMA-NMA. Six English databases (Pubmed, Medline, CINAHL, Embase, the Cochrane library and ProQuest) and four Chinese databases (CNKI, Wanfang, VIP and Sinomed) were searched. Randomized controlled trials (RCTs) and quasi-experimental studies investigating the effects of different frequencies of APE on lower limb hemodynamics published before July 2022 were included. The reference list was also searched. Seven studies (one RCTs and six quasi-experimental studies) were included in the systematic review and five studies (one RCTs and four quasi-experimental studies) were included in the NMA. The risk of bias was assessed using the Cochrane and Joanna Briggs Institute tools. The NMA was performed using the R software (version 4.2.1) and OpenBUGS (version 3.2.3). Results: The results of the NMA showed that a frequency of every 3e4 s the most effective in improving lower extremity hemodynamics (P ¼.85), followed by every 1e2 s (P ¼ .81), every 5e6 s (P¼.32) and less than every 10 s (P ¼.02). Subgroup analysis failed to find a difference between healthy participants and those with unilateral total hip arthroplasty or fracture (MD ¼ À0.23, 95% CI-5.92 to 4.61). Conclusions: Consequencely, for adult patients, with or without lower extremity disease, a frequency of every 3e4 s can be recommended as the optimal frequency of APE in clinical care practice.
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