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This study presents a novel simple model that could quickly simulate the heat transfer of mid-deep buried U-bend pipe ground heat exchangers (MBUGHEs). This model simplified a MBUGHE ...into three independent heat transfer sections: the descending, horizontal, and ascending sections. It was assumed that there was no thermal interference among the different sections because the horizontal pipe was usually very deep and long enough, which meant that each section could be solved separately in independent cylindrical coordinates. CFD software and experimental data were used to validate the established model. The results showed that the model calculation results had high reliability. The model was used to analyze the MBUGHE heat extraction characteristics. The results indicated that the heat extraction capacity increased with the increase of the ground thermal conductivity, ground volumetric heat capacity, buried pipe depth, and horizontal pipe length. The results also showed that the MBUGHE heat extraction capacity had a significant decrease in the first several years, but the decrease was gradually reduced with the increase of the operation time and the decrease became approximately stable after 15 years.
The ultra-fast laser heating process of nano-films is characterized by an ultra-short duration and ultra-small space size, in which the classical Fourier law based on the hypothesis of local ...equilibrium is no longer applicable. Based on the Cattaneo-Vernotte (CV) model and the dual-phase-lag (DPL) model, the two-dimensional analytical solutions of heat conduction in nano-films under ultra-fast laser are obtained using the integral transformation method. The results show that there is a thermal wave phenomenon inside the film, which becomes increasingly evident as the elapse of the lag time of the temperature gradient. Moreover, the wave amplitude in the vertical direction is much larger than that in the horizontal direction of the nano-film. By comparing the numerical result of the two models, it is found that the temperature distribution inside the nano-film based on the DPL model is gentler than that of the CV model. Additionally, the temperature distribution in the two-dimensional solution is lower than that in the one-dimensional solution under the same Knudsen number. In the comparison results of the CV model, the maximum peak difference in the thermal wave reaches 75.08 K when the Knudsen number is 1.0. This demonstrates that the horizontal energy carried by the laser source significantly impacts the temperature distribution within the film.
•Summarized a comprehensive review on developments and advances in three kinds of GHE.•Summarized analytical, numerical and short-term step models of vertical borehole GHE.•Summarized models and ...influencing factors on the performance of PGHE.•Elaborated models of three kinds of deep borehole GHE.
As a renewable energy source, geothermal energy has been widely used to provide space heating and cooling for buildings. The thermal performance of ground heat exchanger (GHE) is significant for the operating efficiency of the ground source heat pump (GSHP) systems. This paper presents a comprehensive review of developments and advances of three kinds of GHE, including vertical borehole GHE (VBGHE), Pile GHE (PGHE), and deep borehole GHE (DBGHE) which are currently popular in larger GSHP systems. Firstly, analytical models proposed to analyze heat transfer process of VBGHE with different geological conditions are summarized, such as homogenous or heterogeneous ground, with or without groundwater advection. Numerical and short-time step models and measures to improve GHE thermal performance are also reviewed. Secondly, a summary of research advances in PGHE is provided, which includes the heat transfer models of PGHE, the effects of geometric structure, operation modes, pile spacing, use of phase change material (PCM), thermal properties of PCM, thermo-mechanical behavior and/or thermal performance of PGHE. The effects of groundwater flow direction and velocity on PGHE are also summarized in brief. Lastly, models of three kinds of DBGHEs, i.e., deep coaxial GHE (DCGHE), deep U-bend GHE (DUGHE) and super-long gravity heat pipe (SLGHP), are reviewed. The physical bases of the different analytical models are elaborated and also their advantages and disadvantages are described. Advances in numerical modelling and improving numerical model calculation speed of DCBHE, DCBHE array, and DUBHE are summarized. The review provides a meaningful reference for the further study of GHEs.
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The superhydrophobic surface has a great advantage of self-cleaning, inhibiting bacterial adhesion, and enhancing anticoagulant properties in the field of biomedical materials. In this paper, a ...superhydrophobic surface was successfully prepared on titanium alloy via high-speed micro-milling, anodic oxidation and fluoroalkylsilane modification. The surface morphology was investigated by scanning electron microscope and a laser scanning microscope. The surface wettability was investigated through the sessile-drop method. Firstly, regular microgrooves were constructed by micro-milling. Then, nanotube arrays were fabricated by anodic oxidation. Afterwards, fluoroalkylsilane was used to self-assemble a monolayer on the surface with a composite micro/nanostructure. Compared to polished titanium samples, the modified samples exhibited superhydrophobic properties with the water contact angle (CA) of 153.7° and the contact angle hysteresis of 2.1°. The proposed method will provide a new idea for the construction of superhydrophobic titanium surgical instruments and implants in the future.
•Zoning operation strategy to alleviate thermal accumulation in GHE fields is proposed.•Zoning operation can diminish thermal accumulation due to unbalanced seasonal thermal load.•The zoning ...operation is more efficient with smaller soil thermal conductivities.
When the heat extraction and injection of a borehole ground heat exchanger (GHE) are not seasonally balanced, ground thermal accumulation will occur and will cause a decline in the ground source heat pump's operational efficiency, especially for large multiple borehole ground heat exchangers (LMBGHE). A zoning operation strategy, in which only the relatively central part of the GHE runs during the low load season, is adopted in this paper to alleviate the thermal accumulation. By analyzing the case in which the heat injected into the ground in the summer is greater than that extracted from the ground in the winter, it was found that, in comparison with the full operation mode, the highest and average field temperatures significantly decrease when only the central part of the GHE runs during the winter. Analysis shows that the thermal accumulation can be effectively alleviated by this GHE zoning operation. This study also indicates that the zoning operation method is more effective when the ground has a smaller thermal conductivity.
Based on the lattice Boltzmann method, this paper simulated the non-equilibrium heat transfer process in nano-silicon thin film under ultrafast laser irradiation. The influence of boundary conditions ...on heat transport was investigated. Results show that under rebound and diffuse boundary conditions, the energy distribution within the film is non-uniform due to interface effects. However, the specular boundary condition is equivalent to eliminating the interface, resulting in a smooth energy distribution. Under convective boundary conditions, the thermal wave phenomenon disappears owing to the open interface. When the energy tends to be stable, the energy density under convective boundary conditions is reduced to 50% of that under adiabatic boundary conditions. As the film size decreases, the differences between boundary conditions become more significant. Particularly when the film size is smaller than the phonon mean free path, the influence of boundary conditions cannot be neglected. Therefore, boundary conditions and size effects are important for the design of nanodevices. Furthermore, compared with the results obtained by the Cattaneo-Vernotte model, it is found that at smaller Knudsen numbers, the Cattaneo-Vernotte model has a better match with the lattice Boltzmann method.
Background:
Paeoniflorin (PF) represents the major bioactive constituent of the traditional Chinese medicine plant
Paeonia suffruticosa
(Ranunculaceae), which has a long history as a folk medicine in ...Asian. Paeoniflorin, a bitter pinene monoterpene glycoside, has antidepressant effects, but its potential therapeutic mechanism has not been thoroughly explored.
Methods:
Experimental depression in rats was established by the chronic unpredictable mild stress (CUMS) combined with orphan method, and the efficacy of paeoniflorin on depression was evaluated by the sucrose preference test and open field test. The antidepressant mechanism of paeoniflorin was investigated by metabolomic and network pharmacology. The relevant pathways of biomarkers highlighted in metabolomics were explored, and the possible targets of paeoniflorin in the treatment of depression were further revealed through network analysis. The binding activity of paeoniflorin to key targets was verified by molecular docking.
Results:
Metabolomics showed that rats with CUMS-induced depression had urine metabolic disorders, which were reversed by paeoniflorin through the regulation of metabolic pathways. Metabolites that play a key role in the function of paeoniflorin include citric acid, thiamine monophosphate, gluconolactone, 5-hydroxyindoleacetic acid and stachyose. Key predicted targets are
SLC6A4
,
TNF
,
IL6
and
SLC6A3
. An important metabolic pathway is the Citrate cycle (TCA cycle).
Conclusion:
Network integrative analysis in this study showed that paeoniflorin could improve depressive-like symptoms in model rats with CUMS-induced depression and overall correct the disordered metabolic profile through multiple metabolic pathways.
The purpose of this study was to associate the anti-inflammatory dietary diversity and depressive symptoms among a nationwide sample of Chinese older adults. We used data from the 2018 wave of ...Chinese longitudinal healthy longevity survey (CLHLS). We assessed depressive symptoms using the 10 items of the center for epidemiologic studies depression scale (CES-D-10). Based on the dietary diversity index (DDI) generated by previous studies, we construct two novel indicators: the protein-enriched dietary diversity index diet (PEDDI) and the anti-inflammatory dietary diversity index diet (AIDDI). We used multivariate logistic models to evaluate the associations of DDI, PEDDI, and AIDDI with depressive symptoms, statistically adjusted for a range of potential confounders. A total of 12,192 participants (mean age 83.6 years) were included in the analysis. We found that participants with a higher score of DDI (OR = 0.91, 95% CI: 0.89-0.92) and PEDDI (OR = 0.91, 95% CI: 0.88-0.93) showed lower odds of having depressive symptoms, while the association between AIDDI and depressive symptoms was more marked (OR = 0.80, 95% CI: 0.78-0.83). The associations remained in subgroup analyses and sensitivity analyses. The results indicate that intaking diversified diet, particularly anti-inflammatory foods, may be associated with a lower risk of depressive symptoms. The findings of this study, if confirmed as causal, provide evidence that an intervention of adopting an anti-inflammatory diversified diet may reduce the burden of depression among older adults.
To examine the bi-directorial association between diversified leisure activity participation and cognitive function over a 7-year period.
Data analyzed was from the Chinese Longitudinal Healthy ...Longevity Survey (CLHLS), a large-scale longitudinal national study. The baseline survey was conducted in 2011 with follow-up every three years. We traced a total of 2718 participants over a period of 7 years. We used adjusted random intercept cross-lagged panel models (RI-CLPMs) to examine the bi-directorial associations between diversified leisure activity participation and cognitive function.
We observed bi-directorial associations between diversity of leisure activity and cognitive function across waves at the between-person and within-person levels. The adjusted random intercept cross-lagged panel models fitted the data appropriately, and the 3-year cross-lagged effects of prior diversified leisure activity participation on cognitive function (β = 0.058, p < 0.01) and cognitive function on subsequent diversified leisure activity participation (β = 0.047, p < 0.05) were significant. The results remained after adjusting the model for baseline sex, age, educational level, marital status and current residence, the number of chronic diseases, ADL, depressive symptoms, sleep quality, smoking, and drinking.
This study suggests that a reciprocal causality relationship between diversified leisure activity participation and cognitive function, indicating a "positive circle" that further promotes cognition over time.
Abstract
Background
It remains unclear whether plant-based or animal-based dietary patterns are more beneficial for older adults more in maintaining muscle mass. Using a prospective cohort with ...nationwide sample of China older adults in this study, we aimed to examine the relationship between adhering to plant-based diet patterns or animal-based diet patterns and muscle loss.
Methods
We included 2771 older adults (≥ 65 years) from the Chinese Longitudinal Health Longevity Survey (CLHLS) with normal muscle mass at baseline (2011 and 2014 waves), which followed up into 2018. Plant-based dietary pattern scores and preference subgroups were constructed using 16 common animal-based and plant-based food frequencies. We used the corrected appendicular skeletal muscle mass (ASM) prediction formula to assess muscle mass. We applied the Cox proportional hazard risk regression to explore associations between dietary patterns and low muscle mass (LMM).
Results
During a mean of 4.1 years follow-up, 234 (8.4%) participants with normal muscle mass at baseline showed LMM. The plant-based dietary pattern reduced the risk of LMM by 5% (Hazard Ratios HR: 0.95, 95% confidence intervals 95%CI: 0.92–0.97). In addition, a high plant-based food company with a high animal-based food intake pattern reduced the risk of LMM by 60% (HR: 0.40, 95% CI: 0.240–0.661) and 73% (HR: 0.27, 95% CI: 0.11–0.61) in the BADL disability and IADL disability population compared with a low plant-based food and high animal-based food intake, whereas a high plant-based food and low animal-based food intake was more beneficial in reducing the risk of LMM in the normal BADL functioning (HR: 0.57, 95% CI: 0.35–0.90) and IADL functioning (HR: 0.51, 95% CI: 0.28–0.91) population.
Conclusions
When it comes to maintaining muscle mass in older Chinese people with functional independence, a plant-based diet pattern is more beneficial and effective than the animal-based one. People with functional dependence may profit from a combination of plant-based and animal-based diets to minimize muscle loss.
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