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| 2. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Liu, Wenjuan, et al.
(författare)
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Strontium-Substituted Dicalcium Silicate Bone Cements with Enhanced Osteogenesis Potential for Orthopaedic Applications
- 2019
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 12:14
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Tidskriftsartikel (refereegranskat)abstract
- Incorporating Sr element in biomaterials for bone implants is an effective way to improve their biological performance, as Sr element has been proved to enhance bone regeneration and depress bone resorption activity. In the present study, we developed a Sr-incorporated dicalcium silicate (C2S) bone cement as a potential candidate for bioactive self-setting bone cement in orthopaedics and stomatology. The Sr-C2S powders containing 0.3-6.8% Sr in molar ratio were prepared by means of chemical co-precipitation, and the results of XRD analysis indicated the incorporation of Sr element into the lattice of C2S. Sr-C2S bone cements, as prepared by mixing the powders with water, have a final setting time of 570 to 594 min, and compressive strength higher than that of C2S bone cement within certain incorporation range. The Sr-C2S bone cements possessed good in vitro bioactivity by inducing apatite formation in simulated body fluid (SBF) within 7 days. Moreover, the proliferation activity of human bone marrow mesenchymal stem cells (hBMSCs) with Sr-C2S bone cements was significantly higher than that with C2S bone cement, and the alkaline phosphatase (ALP) activity of hBMSCs was also enhanced with addition of Sr element in Sr-C2S groups. The Sr-C2S might therefore be a bioactive self-setting material with enhanced biological performance and holds the prospect for application in the bone regeneration area.
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- Luo, Yiqi, et al.
(författare)
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Toward more realistic projections of soil carbon dynamics by Earth system models
- 2016
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Ingår i: Global Biogeochemical Cycles. - 0886-6236. ; 30:1, s. 40-56
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Tidskriftsartikel (refereegranskat)abstract
- Soil carbon (C) is a critical component of Earth system models (ESMs), and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the third to fifth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. First, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by first-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic soil organic C (SOC) dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Second, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based data sets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Third, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable data sets are available to select the most representative model structure, constrain parameters, and prescribe forcing fields.
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| 6. |
- Fang, Xin, et al.
(författare)
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Comparison of Frequentist and Bayesian Generalized Additive Models for Assessing the Association between Daily Exposure to Fine Particles and Respiratory Mortality : A Simulation Study
- 2019
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Ingår i: International Journal of Environmental Research and Public Health. - Basel, Switzerland : MDPI. - 1661-7827 .- 1660-4601. ; 16:5
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To compare the performance of frequentist and Bayesian generalized additive models (GAMs) in terms of accuracy and precision for assessing the association between daily exposure to fine particles and respiratory mortality using simulated data based on a real time-series study.Methods: In our study, we examined the estimates from a fully Bayesian GAM using simulated data based on a genuine time-series study on fine particles with a diameter of 2.5 m or less (PM2.5) and respiratory deaths conducted in Shanghai, China. The simulation was performed by multiplying the observed daily death with a random error. The underlying priors for Bayesian analysis are estimated using the real world time-series data. We also examined the sensitivity of Bayesian GAM to the choice of priors and to true parameter.Results: The frequentist GAM and Bayesian GAM show similar means and variances of the estimates of the parameters of interest. However, the estimates from Bayesian GAM show relatively more fluctuation, which to some extent reflects the uncertainty inherent in Bayesian estimation.Conclusions: Although computationally intensive, Bayesian GAM would be a better solution to avoid potentially over-confident inferences. With the increasing computing power of computers and statistical packages available, fully Bayesian methods for decision making may become more widely applied in the future.
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| 7. |
- Fang, Xin, et al.
(författare)
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Relationship between fine particulate matter, weather condition and daily non-accidental mortality in Shanghai, China : A Bayesian approach
- 2017
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- There are concerns that the reported association of ambient fine particulate matter (PM2.5) with mortality might be a mixture of PM2.5 and weather conditions. We evaluated the effects of extreme weather conditions and weather types on mortality as well as their interactions with PM2.5 concentrations in a time series study. Daily non-accidental deaths, individual demographic information, daily average PM2.5 concentrations and meteorological data between 2012 and 2014 were obtained from Shanghai, China. Days with extreme weather conditions were identified. Six synoptic weather types (SWTs) were generated. The generalized additive model was set up to link the mortality with PM2.5 and weather conditions. Parameter estimation was based on Bayesian methods using both the Jeffreys' prior and an informative normal prior in a sensitivity analysis. We estimate the percent increase in non-accidental mortality per 10 mu g/m(3) increase in PM2.5 concentration and constructed corresponding 95% credible interval (CrI). In total, 336,379 non-accidental deaths occurred during the study period. Average daily deaths were 307. The results indicated that per 10 mu g/m(3) increase in daily average PM2.5 concentration alone corresponded to 0.26-0.35% increase in daily non-accidental mortality in Shanghai. Statistically significant positive associations between PM2.5 and mortality were found for favorable SWTs when considering the interaction between PM2.5 and SWTs. The greatest effect was found in hot dry SWT (percent increase = 1.28, 95% CrI: 0.72, 1.83), followed by warm humid SWT (percent increase = 0.64, 95% CrI: 0.15, 1.13). The effect of PM2.5 on non-accidental mortality differed under specific extreme weather conditions and SWTs. Environmental policies and actions should take into account the interrelationship between the two hazardous exposures.
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| 8. |
- Fu, L., et al.
(författare)
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Effects of Cr3C2 content and temperature on sliding friction and wear behaviors of Cr3C2/Ni3Al composite materials
- 2018
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 414-415, s. 163-173
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Tidskriftsartikel (refereegranskat)abstract
- Chromium carbide (Cr3C2)-reinforced Ni3Al matrix composites, which possess excellent high-temperature strength and wear resistance, are considered as potential high-temperature wear-resistant materials. In this study, effects of Cr3C2content on the friction and wear properties of Cr3C2/Ni3Al composites and their counterpart gray cast iron disks were investigated at different temperatures. The worn surface morphologies of the Cr3C2/Ni3Al composites and gray cast iron disks were analyzed to understand their wear mechanisms. The analysis results showed that in the Ni3Al matrix composites, a combination of abrasive wear and adhesive wear occurred at room temperature, whereas adhesive wear was severer at 200 °C. Furthermore, the optimum Cr3C2contents of the Cr3C2/Ni3Al composites were found to be 18 vol% and 12 vol% at room temperature and 200 °C, respectively. The volume loss of the composites increased with an increase in the fraction of the Cr3C2strengthening phase at 350 °C. The wear resistance of the gray cast iron disks decreased with an increase in temperature. In contrast, the wear resistance of the Ni3Al matrix composites increased with an increase in temperature. This increased wear resistance of the composites is attributed to the transformation of their wear mechanism with increasing temperature.
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| 9. |
- Fu, L., et al.
(författare)
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Microstructure and tribological properties of Cr3C2/Ni3Al composite materials prepared by hot isostatic pressing (HIP)
- 2017
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 115:115, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- Ni3Al-based composites with different Cr3C2 contents were fabricated by the hot isostatic pressing (HIP) technique.The microstructure, phase constitution, and tribological properties of the composites were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and pin-on-disk wear tests. The results revealed that the strengthening phase is distributed homogeneously in the Ni3Al matrix. During the HIP process, M7C3 (M = Cr, Fe) is formed by diffusion of Fe, C, and Cr to the interface between the Cr3C2 particles and Ni3Al matrix. The diffusion process binds the phases and is important for improving the wear resistance of Cr3C2/Ni3Al composites. The wear measurements demonstrated that micro-cutting and fatigue wear are the dominant mechanisms for this tribological pair. The wear resistance of Cr3C2/Ni3Al composites is significantly improved by the addition of Cr3C2 particles.When the content of Cr3C2 is within a certain range, the wear resistance of Cr3C2/Ni3Al composites increases as the Cr3C2 content increases. However, the addition of excess Cr3C2 (for example, 24 vol% in this work) could lead to a decrease in the wear resistance of the composites. In addition, the average friction coefficients and wear of the counterpart decrease with increasing Cr3C2 addition.
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| 10. |
- Guo, Weiwei, et al.
(författare)
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Aerodynamic effect of wind barriers and running safety of trains on high-speed railway bridges under cross winds
- 2015
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Ingår i: Wind and Structures. - : Techno-Press. - 1226-6116 .- 1598-6225. ; 20:2, s. 213-236
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Tidskriftsartikel (refereegranskat)abstract
- For high-speed railways (HSR) in wind prone regions, wind barriers are often installed on bridges to ensure the running safety of trains. This paper analyzes the effect of wind barriers on the running safety of a high-speed train to cross winds when it passes on a bridge. Two simply-supported (S-S) PC bridges in China, one with 32 m box beams and the other with 16 m trough beams, are selected to perform the dynamic analyses. The bridges are modeled by 3-D finite elements and each vehicle in a train by a multi-rigid-body system connected with suspension springs and dashpots. The wind excitations on the train vehicles and the bridges are numerically simulated, using the static tri-component coefficients obtained from a wind tunnel test, taking into account the effects of wind barriers, train speed and the spatial correlation with wind forces on the deck. The whole histories of a train passing over the two bridges under strong cross winds are simulated and compared, considering variations of wind velocities, train speeds and without or with wind barriers. The threshold curves of wind velocity for train running safety on the two bridges are compared, from which the windbreak effect of the wind barrier are evaluated, based on which a beam structure with better performance is recommended.
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