Numerical Experiments on the Impacts of Surface Evaporation and Fractionation Factors on Stable Isotopes in Precipitation

Xinping Zhang,Huade Guan,Xinzhu Zhang,Wanjun Zhang,Tianci Yao 한국기상학회 2016 Asia-Pacific Journal of Atmospheric Sciences Vol.52 No.3

The isotope enabled atmospheric water balance model is applied to examine the spatial and temporal variations of δ18O in precipitation, amount effect and meteoric water lines (MWL) under four scenarios with different fractionation nature and surface evaporation inputs. The experiments are conducted under the same weather forcing in the framework of the water balance and stable water isotope balance. Globally, the spatial patterns of mean δ18O and global MWLs simulated by four simulation tests are in reasonably good agreement with the Global Network of Isotopes in Precipitation observations. The results indicate that the assumptions of equilibrium fractionation for simulating spatial distribution in mean annual δ18O and the global MWL, and kinetic fractionation in simulating δ18O seasonality are acceptable. In Changsha, four simulation tests all reproduce the observed seasonal variations of δ18O in precipitation. Compared with equilibrium fractionation, the depleted degree of stable isotopes in precipitation is enhanced under kinetic fractionation, in company with a decrease of isotopic seasonality and inter-event variability. The alteration of stable isotopes in precipitation caused by the seasonal variation of stable isotopes in vapour evaporated from the surface is opposite between cold and warm seasons. Four simulations all produce the amount effect commonly observed in monsoon areas. Under kinetic fractionation, the slope of simulated amount effect is closer to the observed one than other scenarios. The MWL for warm and humid climate in monsoon areas are well simulated too. The slopes and intercepts of the simulated MWLs decrease under kinetic fractionation.

Enhanced photocatalytic mechanism of Ag₃PO₄ nano-sheets using MS₂ (M = Mo, W)/rGO hybrids as co-catalysts for 4-nitrophenol degradation in water

Zhang, Weiping,Li, Guiying,Wang, Wanjun,Qin, Yaxin,An, Taicheng,Xiao, Xinyan,Choi, Wonyong Elsevier 2018 Applied Catalysis B Vol.232 No.-

<P><B>Abstract</B></P> <P>A chemically modified Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>(M = Mo, W)/rGO composite was firstly synthesized via a liquid-exfoliation solvothermal method. The structure, morphology, optical properties and composition were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, UV–vis diffuse reflectance spectra and X-ray photoelectron spectroscopy, respectively. The characterization results indicated that compact structure could be obtained by using this typical method due to in-situ chemical modification, which could also control the sizes of Ag<SUB>3</SUB>PO<SUB>4</SUB> nano-sheets by adding MS<SUB>2</SUB>/rGO hybrids. More importantly, the resultant Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO composite exhibited higher photocatalytic activity and stability toward the degradation of 4-nitrophenol than pure Ag<SUB>3</SUB>PO<SUB>4</SUB> under sunlight irradiation. The stable structure of Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO was closely related with Z-scheme electronic structure and electrical conductivity of MS<SUB>2</SUB>/rGO hybrids, leading to a higher consumption and transfer of photogenerated electrons. However, by controlling the amounts of MS<SUB>2</SUB>/rGO hybrids, more stable but lower photocatalytic activity composites could be obtained. Further analysis found that the holes and O<SUB>2</SUB> <SUP>−</SUP> were the main reactive species involved in the photocatalytic degradation of 4-nitrophenol. In addition, possible photocatalytic degradation pathways of 4-nitrophenol were also proposed based on the identified intermediates. The findings of this work may provide a new method to design efficient composites for photocatalytic degradation of organic pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO catalyst was fabricated via a liquid-exfoliation solvothermal method. </LI> <LI> Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO has high photocatalytic activity and stability under sunlight. </LI> <LI> The stability of Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO was due to its rapid transfer of photogenerated e<SUP>−</SUP>. </LI> <LI> h<SUP>+</SUP> and O<SUB>2</SUB> <SUP>−</SUP> were the main RSs in photocatalytic degradation of 4-nitrophenol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Research on Hybrid Dynamic Capacitor-a novel approach to VAR compensation and resonance suppression

Zhang Kai,Lei Wanjun,Cheng Nie,Yue Wang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In this paper, a control method named hybrid dynamic capacitor is proposed to provide dynamic VAR compensation and suppress resonance between power capacitor and system inductance in power distribution network. This paper explains the theory of hybrid dynamic capacitor and this method benefits by reducing the initial cost, switching loss and less harmonic current. Finally, simulation and experiment results are given to verify the viability and effectiveness of the hybrid dynamic capacitor and its compensation characteristic.

Preparation of γ-alumina nanoparticle modified polyacrylamide composite and study on its solid phase extraction of Sunset Yellow

Wanjun Li,Qiong Jia,Zhenyu Zhang,Yuanpeng Wang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.4

An organic-inorganic composite, γ-alumina nanoparticle modified polyacrylamide, was synthesized in this study. The composite was characterized by scanning electron microscope, nitrogen adsorption-desorption measurement, thermal gravimetric analyzer, differential scanning calorimetry, and Fourier-transformed infrared spectrometer. A novel solid-phase extraction method with the synthesized composite as the adsorbent was developed for the enrichment of Sunset Yellow coupled with ultraviolet-visible spectrophotometry. To obtain the optimum extraction efficiency, the experimental parameters in the processes of preparation of the adsorbent and solid-phase extraction were studied including synthesis temperature, synthesis time, the dosage of γ-alumina nanoparticles, sample flow rate, sample pH, eluant concentration, and eluant flow rate. Under the optimum conditions, the detection limit of the developed method was calculated to be 0.037 μg mL−1 with intra-day and inter-day relative standard deviation values of 2.57% and 3.89%, respectively. When the method was applied to the determination of Sunset Yellow in beverages, satisfactory recoveries were obtained in the range of 92.3-109.8%.

Leakage and rotordynamic performance of a mixed labyrinth seal compared with that of a staggered labyrinth seal

Mingjie Zhang,Jian Gang Yang,Wanjun Xu,Yalei Xia 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5

Minimizing unwanted leakage between stationary and rotating parts is the main function of annular seals. A Mixed labyrinth seal (MLS) with two specially designed lateral teeth installed on a Staggered labyrinth seal (SLS) is proposed to improve seal performance. A 3D computational fluid dynamics calculation model of MLS is set up. The twin vortex structure that appears in the seal cavity and flow path is more complicated in MLS than in SLS. MLS reduces leakage by about 30 % compared with SLS. Rotordynamic analysis of MLS is also conducted by calculating cross-coupled stiffness. The cross-coupled stiffness of MLS is about 75 % to 85 % that of SLS. The dependence of seal performance on the parameters of the lateral teeth is investigated through a simulation test. The lateral teeth should be set in the middle of the seal cavity, and the gap between the two lateral teeth should be similar to the tip clearance.

Protocatechuic Aldehyde Represses Proliferation and Migration of Breast Cancer Cells through Targeting C-terminal Binding Protein 1

Yu Deng,Wanjun Guo,Guancheng Li,Shuang Li,Hong Li,Xinyan Li,Bei Niu,Mingzhu Song,Yamei Zhang,Zhijian Xu,Fulun Li 한국유방암학회 2020 Journal of breast cancer Vol.23 No.1

Purpose: C-terminal binding protein 1 (CtBP1) is a transcriptional co-repressor that is overexpressed in many cancers. CtBP1 transcriptionally represses a broad array of tumor suppressors, which promotes cancer cell proliferation, migration, invasion, and resistance to apoptosis. Recent studies have demonstrated that CtBP1 is a potential target for cancer therapy. This study was designed to screen for compounds that potentially target CtBP1. Methods: Using a structure-based virtual screening for CtBP1 inhibitors, we found protocatechuic aldehyde (PA), a natural compound found in the root of a traditional Chinese herb, Salvia miltiorrhiza, that directly binds to CtBP1. Microscale thermophoresis assay was performed to determine whether PA and CtBP1 directly bind to each other. Further, clustered regularly interspaced short palindromic repeats associated Cas9 nuclease-mediated CtBP1 knockout in breast cancer cells was used to validate the CtBP1 targeting specificity of PA. Results: Functional studies showed that PA repressed the proliferation and migration of breast cancer cells. Furthermore, PA elevated the expression of the downstream targets of CtBP1, p21 and E-cadherin, and decreased CtBP1 binding affinity for the promoter regions of p21 and E-cadherin in breast cancer cells. However, PA did not affect the expression of p21 and E-cadherin in the CtBP1 knockout breast cancer cells. In addition, the CtBP1 knockout breast cancer cells showed resistance to PA-induced repression of proliferation and migration. Conclusion: Our findings demonstrated that PA directly bound to CtBP1 and inhibited the growth and migration of breast cancer cells through CtBP1 inhibition. Structural modifications of PA are further required to enhance its binding affinity and selectivity for CtBP1.

Research on Multi-frequency Current Tracking Control of Three-phase Grid-connected VSI

Chongfu XU,Wanjun LEI,Gaidi NING,Xiang ZHANG,Yue WANG,Jinjun LIU 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper proposes a multi-frequency current tracking control method which can be applied in the application of APF(Active Power Filter), programmable current source etc. Because the method based on the stationary PI inner loop and the dq outer loop can’t be used in the case of high frequency, a new method is proposed. The proposed method includes a stationary PI inner loop and an Amplitude-Phase outer loop, which can realize separate control of each harmonic in each phase precisely in a wide frequency range, and keep the advantages of the stationary PI method: the anti-interference ability, low harmonic distortion in the line current, fast response speed and simple control. The parameter design method of both loops is also described. At last, simulation results based on PSCAD/EMTDC and experimental results are given to prove the feasibility of this method.

Modeling and Analysis of Harmonic Resonance in Microgrid and Research of Active Harmonic Resistance Method

Cheng Nie,Wanjun Lei,Huajia Wang,Kai Zhang,Yue Wang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In the microgrid, the capacitive element such as compensation capacitor may resonance with the line inductance in harmonic frequency, furthermore serious harmonic resonance may endanger the system. In this paper, resonance mode analysis (RMA) method is used to analysis the harmonic resonance in the microgrid. To suppress the amplified of harmonic current near resonance frequency, an improved current control method for active harmonic resistance (AHR) is proposed. Simulation and experimental results reveal that the proposed method can suppress the resonance in the microgrid effectively.

Analysis of Harmonic Transfer Characteristics and RAPF Installation Strategy in Power Systems

Tian Li,Wanjun Lei,Nie Cheng,Xiaojie Zhang,Guoqing Gao,F. Kai Li 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Power quality has become a new threat because of the distributed nature of disturbances caused by nonlinear loads and DGs. When harmonics are transmitted in a distribution network, they’ll be magnified by resonance between line capacitance and inductance, then worsen the harmonic in power systems. In this paper, a mathematical model for harmonic transfer characteristics of power system feeders is firstly established. Meanwhile, analyze the harmonic voltage propagation caused respectively by the background harmonic voltage source and harmonic current source, which provides an important theoretical basis for the treatment of harmonic pollution. In addition, a strategy is proposed to guide the optimal installation position and setting of external resistance of RAPF to achieve the minimum total distortion rate in the entire distribution network system, which can damp the harmonic resonant effectively. Simulation and experiments have been performed to verify the theoretical analysis and demonstrate the effectiveness of the proposed strategy.