Extraction of Phthalate Esters in Environmental Water Samples Using Layered-Carbon Magnetic Hybrid Material as Adsorbent Followed by Their Determination with HPLC

Wang, Weina,Wu, Qiuhua,Zang, Xiaohuan,Wang, Chun,Wang, Zhi Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.10

In this paper, a layered-carbon-$Fe_3O_4$ (LC-$Fe_3O_4$) hybrid material was synthesized through a facile one-pot solvothermal method and used as the adsorbent for the preconcentration of some phthalate esters (dimethyl phthalate, diethyl phthalate, diallyl phthalate, diisobutyl phthalate and benzyl butyl phthalate) in water samples. The effects of the adsorbent dosage, extraction time, the solution pH and salinity on the adsorption of the phthalate esters (PAEs) were investigated. The magnetic nanocomposite adsorbent could remove and enrich the PAEs from water samples efficiently. After the adsorption, the analytes were desorbed and then determined by high performance liquid chromatography-ultraviolet detection. Under the optimum conditions, the enrichment factors of the method for the analytes were in the range from 161 to 180. A linear response with peak area as the quantification signal was observed in the concentration range from 0.5 to $100ng\;mL^{-1}$. The limits of detection (S/N = 3) of the method were between 0.08 and $0.1ng\;mL^{-1}$. The method was suitable for the determination of trace phthalate esters in environmental water samples.

Structure and Electrical Performance of Na₂C₆O₆ under High Pressure

Wang, Xuan,Zhang, Peijie,Tang, Xingyu,Guan, Junjie,Lin, Xiaohuan,Wang, Yajie,Dong, Xiao,Yue, Binbin,Yan, Jinyuan,Li, Kuo,Zheng, Haiyan,Mao, Ho-kwang American Chemical Society 2019 The Journal of Physical Chemistry Part C Vol. No.

<P>Sodium rhodizonate (Na<SUB>2</SUB>C<SUB>6</SUB>O<SUB>6</SUB>) has very high theoretical capacity as a positive electrode material of sodium-ion batteries, but it still has problems such as low actual capacity and poor electronic/ionic conductivity. In order to improve its conductivity, we investigated its structure and electrical properties under high pressure. By performing in situ X-ray diffraction, Raman, infrared absorption, and alternating current impedance spectroscopy in the range of 0-30 GPa at room temperature, we observed a phase transition at ∼11 GPa, with the conductivity increasing by an order of magnitude. Above ∼20 GPa, Na<SUB>2</SUB>C<SUB>6</SUB>O<SUB>6</SUB> gradually amorphized. During the decompression process, the pressure regulation of the structure and properties of the material are reversible. Our study shows that applying external pressure is an effective tool to improve the conductivity of molecular battery materials. The investigation will help to obtain next-generation electrode materials.</P> [FIG OMISSION]</BR>

Non-devastating Islanding Detection for Micro-grid Based on Mathematical Statistics

Xiaohuan Wang,Chunjiang Zhang,Wenchao Zhao,Xiao Mu 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

Conventional passive islanding detection methods have disadvantages of non-detection zone (NDZ). Active ones can reduce or eliminate NDZ, but their operation mechanism is forcing the voltage or frequency into the fault range, which is a devastating islanding detection approach. However, the non-devastating islanding method without NDZ is desirable for micro-grid applications. A novel active islanding detection method based on mathematical statistics for three-phase inverter is proposed. In this paper, 0-1 sequence is used to modulate the PWM modulation wave by amplitude adjustment. Then the voltage of point of common coupling (PCC) is sampled and the variance based on mathematics features is calculated in real-time. According to the value of variance, the islanding can be determined. The proposed method not only conquers the disadvantage of the destroy that conventional active islanding detection methods result in to the utility grid, but also detects the islanding effectively when the DG power production match to the load power requirement. And it is quick and effective under the ideal and non-ideal utility grid and the false islanding also can be prevented. Simulation and experiment results verify the correctness and feasibility of the proposed method. This method is suitable for the grid-connected /stand-alone dual-mode micro-grid system.

Suppression and stability analysis of frequency coupling effect in grid‑connected inverters

Xiaohuan Wang,Aihua Yang,Yang Liu,Xiaojun Zhao 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.6

With the proposal of the “dual carbon target” in China, the rapid development of renewable energy, mainly photovoltaic and wind power, has been promoted. However, a large amount of renewable energy connected to a grid results in its proportion in the power system going from a low state to a high state. Under a high proportion, the asymmetry of the control structure or parameters in the three-phase grid-connected inverter controller lead to a strong coupling relationship between the sub/super synchronous frequency components, or frequency coupling effect (FCE). This phenomenon can deteriorate the power quality of the inverter system, amplify the harm of frequency oscillation, and even cause system disassembly. To solve the above problems, a unified impedance model considering the FCE induced by the phase-locked loop (PLL), the current loop (CL), and the power outer loop (POL) is established. Based on the established output impedance model, a parameter optimization theoretical analysis method is designed considering the critical stability of the PLL bandwidth and the CL asymmetry degree. Meanwhile, an improved control strategy for the PLL and the POL is proposed. Experimental results show that the proposed parameter optimization and structure improvement strategies can effectively suppress the infl uence of frequency coupling and enhance system stability. Finally, simulation and experimental results verify the correctness of the theoretical analysis and the eff ectiveness of the proposed strategy.

Extraction of Phthalate Esters in Environmental Water Samples Using Layered-Carbon Magnetic Hybrid Material as Adsorbent Followed by Their Determination with HPLC

Weina Wang,Qiuhua Wu,Xiaohuan Zang,Chun Wang,Zhi Wang 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.10

In this paper, a layered-carbon-Fe3O4 (LC-Fe3O4) hybrid material was synthesized through a facile one-pot solvothermal method and used as the adsorbent for the preconcentration of some phthalate esters (dimethyl phthalate, diethyl phthalate, diallyl phthalate, diisobutyl phthalate and benzyl butyl phthalate) in water samples. The effects of the adsorbent dosage, extraction time, the solution pH and salinity on the adsorption of the phthalate esters (PAEs) were investigated. The magnetic nanocomposite adsorbent could remove and enrich the PAEs from water samples efficiently. After the adsorption, the analytes were desorbed and then determined by high performance liquid chromatography-ultraviolet detection. Under the optimum conditions, the enrichment factors of the method for the analytes were in the range from 161 to 180. A linear response with peak area as the quantification signal was observed in the concentration range from 0.5 to 100 ng mL−1. The limits of detection (S/N = 3) of the method were between 0.08 and 0.1 ng mL−1. The method was suitable for the determination of trace phthalate esters in environmental water samples.

Psychological Resilience of Second-Pregnancy Women in China: A Cross-sectional Study of Influencing Factors

Xiaohuan Jin,Xinyuan Xu,Junyan Qiu,Zexun Xu,Lixue Sun,Zhilin Wang,Ling Shan 한국간호과학회 2021 Asian Nursing Research Vol.15 No.2

Purpose The aim of the study was to evaluate the status of psychological resilience among women in their second pregnancy and to investigate the possible influencing factors. Methods A total of 275 women in their second pregnancy and who met the criteria were surveyed from two public hospitals in China from July 2018 to January 2019. The instruments included the General Self-designed Questionnaire, Connor–Davidson Resilience Scale, Social Support Rate Scale, and 36-item Pregnancy Stress Rating Scale. Results The total psychological resilience score of second-pregnancy women was relatively low. Multivariate regression analysis identified five factors associated with psychological resilience: intimacy with husbands, social support utilization, gender of the first child, high-risk pregnancy of the first child, and the stress caused by worrying about the health and safety of the mother and fetus. Conclusion Women in their second pregnancy represent a unique population, and their low psychological resilience score deserves attention. Identification of factors contributing to decreased psychological resilience may enable us to design prevention and intervention strategies and to deliver specific psychological supports to pregnant women at high risk of developing negative psychology.

On Finsler metrics of constant S-curvature

Xiaohuan Mo,Xiaoyang Wang 대한수학회 2013 대한수학회보 Vol.50 No.2

In this paper, we study Finsler metrics of constant S-curva- ture. First we produce infinitely many Randers metrics with non-zero (constant) S-curvature which have vanishing H-curvature. They are counterexamples to Theorem 1.2 in [20]. Then we show that the existence of (α, β)-metrics with arbitrary constant S-curvature in each dimension which is not Randers type by extending Li-Shen’ construction.

ON FINSLER METRICS OF CONSTANT S-CURVATURE

Mo, Xiaohuan,Wang, Xiaoyang Korean Mathematical Society 2013 대한수학회보 Vol.50 No.2

In this paper, we study Finsler metrics of constant S-curvature. First we produce infinitely many Randers metrics with non-zero (constant) S-curvature which have vanishing H-curvature. They are counterexamples to Theorem 1.2 in [20]. Then we show that the existence of (${\alpha}$, ${\beta}$)-metrics with arbitrary constant S-curvature in each dimension which is not Randers type by extending Li-Shen' construction.

Computer simulation of the nonlinear static behavior of axially functionally graded microtube with porosity

Li, Xiaohuan,Wang, Tian,Liu, Fang,Zhu, Zhiwen Techno-Press 2021 Advances in nano research Vol.11 No.4

Static analysis of microstructures, including bending and buckling, is widely practiced in the fabrication and creation of applications such as actuation, sensing, and energy recovery. This article aims to inquire about the static behavior of non-uniform and imperfect microtubes through a numerical solution. Based on the modified couple stress theory, the first-order shear deformation theory and Von-Karman nonlinear theory, and employing the energy conservation method, the linear and nonlinear governing equations are derived. The porosity-dependent material in both ceramic and metal phases makes the functionally graded materials which are varied along tube length, moreover, cross-sections are also considered uniform and nonuniform via three valuable functions. Finally, the linear and nonlinear equations are solved utilizing the generalized differential quadrature method (GDQM) coupled with the numerical iteration method.

The association between obesity and glaucoma in older adults: evidence from the China Health and Retirement Longitudinal Study

Zhao Xiaohuan,Bo Qiyu,Sun Junran,Chen Jieqiong,Li Tong,Huang Xiaoxu,Zhou Minwen,Wang Jing,Liu Wenjia,Sun Xiaodong 한국역학회 2023 Epidemiology and Health Vol.45 No.-

Objectives: This study evaluated the association between obesity and glaucoma in middle-aged and older people. A population-based retrospective cohort study was conducted using data from the China Health and Retirement Longitudinal Study.Methods: Glaucoma was assessed via self-reports. Multivariate logistic regression analysis and a Cox proportional hazards model were used to assess the relationship between obesity and glaucoma risk.Results: Older men living in urban areas who were single, smokers, and non-drinkers were found to have a significantly higher incidence of glaucoma (all P<0.05). Diabetes, hypertension, and kidney disease were also associated with higher glaucoma risk, while dyslipidemia was associated with lower risk (all P<0.05). After the model was adjusted for demographic, socio-economic, and health-related variables, obesity was significantly associated with a 10.2% decrease in glaucoma risk according to the Cox proportional hazards model (hazard ratio, 0.898; 95% CI, 0.829-0.973) and an 11.8% risk reduction in the multivariate logistic regression analysis (odds ratio, 0.882; 95% CI, 0.803-0.968). A further subgroup analysis showed that obesity was associated with a reduced risk of glaucoma in people living in rural areas, in smokers, and in those with kidney disease (all P<0.05). Obesity also reduced glaucoma risk in people with diabetes, hypertension, or dyslipidemia more than in healthy controls (all P<0.05).Conclusions: This cohort study suggests that obesity was associated with a reduced risk of glaucoma, especially in rural residents, smokers, and people with kidney disease. Obesity exerted a stronger protective effect in people with diabetes, hypertension, or dyslipidemia than in healthy people.