Study on the Mechanical Properties of Functional Graphene/Polyethylene Composites by Molecular Dynamics Simulation

Yuanyuan Qin,Yifei Wang,Jin Liu,Fengfeng Chen,Aiying Yao,Zhanchun Chen,Fu Junyu 한국고분자학회 2022 Macromolecular Research Vol.30 No.12

The mechanical properties of functionalized graphene/polyethylene (f- GRA/PE) composites and graphene/polyethylene (GRA/PE) composites were studied based on the crystallized models with the molecular dynamics simulation in this paper. The effects of GRA and f-GRA with different mass fractions on the mechanical properties of polyethylene were considered. The results showed that the adsorption capacity of polyethylene molecular chains of f-GRA is stronger, the compatibility of f-GRA/PE system is higher with decreasing the interface distance, and the dynamic property of molecular chain is weaker with reducing the radius of gyration of f-GRA/ PE. Furthermore, the reduction of mechanical energy consumption results in the increase of wear resistance of the system, which is more obvious when the mass fraction of f-GRA increases. Finally, the influence of different tensile rates on the composite system was studied. It was found that during the tensile process, the ability of the composite material to resist deformation in the stretching direction is enhanced, and the functionalized graphene inhibits the movement of the molecular chain due to the adsorption force, which improves the yield stress of the f-GRA/PE composite material, thereby increasing the tensile strength. Tensile rate has a certain effect on mechanical properties, and elastic modulus and yield stress increase with the increase of strain rate.

Energy Efficient Air-to-Ground Communication Networks with Reconfigurable Intelligent Surface

Yuanyuan Yao,Ke Lv,Nan Ma,Xinwei Yue,Xiaoqi Qin,Xiang Yun 한국통신학회 2022 Journal of communications and networks Vol.24 No.5

Reconfigurable intelligent surface (RIS) assisted air- to-ground wireless powered communication networks (WPCNs) are constructed to promote the energy efficiency of the system, in which unmanned aerial vehicles (UAV) reflects energy towards the energy-constrained hybrid access points (HAP) through RIS. Subsequently, HAP uses the collected energy to communicate with users in blind areas through the RIS-UAV. By optimizing parameters such as charging time ratio, transmit power and phase shifts matrix, the energy efficiency for single and multi- user scenarios are maximized, respectively. The energy efficiency is modeled as a non-convex quadratic programming problem with inequality constraints in the single-user scenario. Then the problem is converted into an equivalent convex problem by using the Taylor expansion and convex approximation method. A joint optimization algorithm of power and phase shifts is proposed to obtain a feasible solution. The energy efficiency is modeled as a fractional programming problem with non-convex inequality constraints in the multi-user scenario, and the feasible solution is obtained by proposing an alternating algorithm. Finally, both two scenarios are compared with the system of traditional amplify- and-forward (AF) relay, respectively. Finally, the simulation results show that the proposed algorithms can provide up with 150% and 160% improvement of the energy efficiency in the single and multi-user scenarios, respectively, compared to the traditional AF relay.

Effect of La2O3 promoter on NiO/Al2O3 catalyst in CO methanation

Hongyun Qin,Cuili Guo,Yuanyuan Wu,Juntao Zhang 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.7

A series of NiO/Al2O3 catalysts promoted by different La2O3 contents were prepared by impregnation method. The physicochemical properties of NiO-La2O3/Al2O3 were characterized by N2 adsorption-desorption, X-ray diffraction(XRD), H2 temperature programmed reduction (H2-TPR) and H2 chemisorption. The effect of La2O3 on the activityof NiO/Al2O3 for CO methanation was investigated in a fixed bed reactor. A lifetime test, as well as thermogravimetric(TG) analysis, was performed to investigate the stability performance and anti-carbon deposition of catalysts. Theresults showed that the addition of La2O3 can restrain the growth of NiO particles, increase the H2 uptake and Ni dispersion,and therefore enhance the activity of catalysts. When the La2O3 content was 3 wt%, a CO conversion of 98%and a selectivity to CH4 of 96% were obtained at 400 oC. Furthermore, the catalyst NiO-La2O3/Al2O3 with 3 wt% La2O3content displayed highly stable performance in long-term tests, especially exhibiting good anti-carbon deposition property.

Investigating the miscibility of poly (butylene adipate-co-terephthalate)/poly (lactic acid) mixtures through multi-scale simulation and experiments

Xuezhi Li,Yuanyuan Qin,Haojie Li,Guangjun Liu,Junyu Fu,Feng Li,Zhanchun Chen 한국고분자학회 2023 Macromolecular Research Vol.31 No.9

The processability and practical applications of poly (butylene adipate-co-terephthalate) (PBAT) /poly (lactic acid) (PLA) blends are limited due to their lower miscibility. To investigate the miscibility of various PBAT/PLA composite ratios and the mechanism of miscibility between them, PBAT/PLA blends with different ratios were prepared using the melt mixing method. A combination of multi-scale simulations and experiments were employed to investigate the miscibility of the composites. Molecular dynamics simulations analyzed PBAT/PLA mixtures that are incompatible and showed the molecular basis of their incompatibility through the radial distribution function (RDF). The degree of miscibility of different ratios of PBAT/PLA composites was described using the Flory–Huggins interaction parameter, indicating that the 50/50 PBAT/PLA blend has the worst miscibility. Mesoscopic dynamics described the mesoscopic morphology of PBAT and PLA blends visually. The results obtained from the simulations were consistent with scanning electron microscope (SEM) and differential scanning calorimeter (DSC) experiments, indicating the simulations' reliability. This work provides a molecular perspective on the mechanism of thermodynamic insolubility of PBAT and PLA, which can inspire future PBAT/PLA hybrid modifications.

Peroxopolyoxotungsten-based Ionic Hybrid as a Highly Efficient Recyclable Catalyst for Epoxidation of Vegetable oil with H₂O₂

Wu, Jianghao,Jiang, Pingping,Qin, Xiaojie,Ye, Yuanyuan,Leng, Yan Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.6

A peroxopolyoxotungsten-based ionic hybrid was synthesized by anion-change of peroxopolyoxometalate (POM) $PW_4O{_{24}}^{3-}$ with dicationic long-chain alkyl imidazolium ionic liquids. The characterization was conducted by FT-IR, TGA, $^1H$-NMR and CHN Elemental analyses. Its catalytic performance was evaluated by the epoxidation of soybean oil with $H_2O_2$ under solvent-free condition, including testing of organic cations influence, catalytic reusability and reaction conditions. The catalyst was proved to be a highly efficient recyclable catalyst for epoxidation of various vegetable oils with $H_2O_2$, showing high $H_2O_2$ utilization efficiency, high catalytic activity, convenient recovery and good reuse ability.

Peroxopolyoxotungsten-based Ionic Hybrid as a Highly Efficient Recyclable Catalyst for Epoxidation of Vegetable oil with H2O2

Jianghao Wu,Pingping Jiang,Xiaojie Qin,Yuanyuan Ye,Yan Leng 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.6

A peroxopolyoxotungsten-based ionic hybrid was synthesized by anion-change of peroxopolyoxometalate (POM) PW4O24 3− with dicationic long-chain alkyl imidazolium ionic liquids. The characterization was conducted by FT-IR, TGA, 1H-NMR and CHN Elemental analyses. Its catalytic performance was evaluated by the epoxidation of soybean oil with H2O2 under solvent-free condition, including testing of organic cations influence, catalytic reusability and reaction conditions. The catalyst was proved to be a highly efficient recyclable catalyst for epoxidation of various vegetable oils with H2O2, showing high H2O2 utilization efficiency, high catalytic activity, convenient recovery and good reuse ability.

Feasibility of a Clinical-Radiomics Model to Predict the Outcomes of Acute Ischemic Stroke

Zhou Yiran,Wu Di,Yan Su,Xie Yan,Zhang Shun,Lv Wenzhi,Qin Yuanyuan,Liu Yufei,Liu Chengxia,Lu Jun,Li Jia,Zhu Hongquan,Liu Weiyin Vivian,Liu Huan,Zhang Guiling,Zhu Wenzhen 대한영상의학회 2022 Korean Journal of Radiology Vol.23 No.8

Objective: To develop a model incorporating radiomic features and clinical factors to accurately predict acute ischemic stroke (AIS) outcomes. Materials and Methods: Data from 522 AIS patients (382 male [73.2%]; mean age ± standard deviation, 58.9 ± 11.5 years) were randomly divided into the training (n = 311) and validation cohorts (n = 211). According to the modified Rankin Scale (mRS) at 6 months after hospital discharge, prognosis was dichotomized into good (mRS ≤ 2) and poor (mRS > 2); 1310 radiomics features were extracted from diffusion-weighted imaging and apparent diffusion coefficient maps. The minimum redundancy maximum relevance algorithm and the least absolute shrinkage and selection operator logistic regression method were implemented to select the features and establish a radiomics model. Univariable and multivariable logistic regression analyses were performed to identify the clinical factors and construct a clinical model. Ultimately, a multivariable logistic regression analysis incorporating independent clinical factors and radiomics score was implemented to establish the final combined prediction model using a backward step-down selection procedure, and a clinical-radiomics nomogram was developed. The models were evaluated using calibration, receiver operating characteristic (ROC), and decision curve analyses. Results: Age, sex, stroke history, diabetes, baseline mRS, baseline National Institutes of Health Stroke Scale score, and radiomics score were independent predictors of AIS outcomes. The area under the ROC curve of the clinical-radiomics model was 0.868 (95% confidence interval, 0.825–0.910) in the training cohort and 0.890 (0.844–0.936) in the validation cohort, which was significantly larger than that of the clinical or radiomics models. The clinical radiomics nomogram was well calibrated (p > 0.05). The decision curve analysis indicated its clinical usefulness. Conclusion: The clinical-radiomics model outperformed individual clinical or radiomics models and achieved satisfactory performance in predicting AIS outcome