The Effect of Impeller Indent Distance on the Performance of Vortex Pumps

Lei DAI,Lei GU,Jun WANG,Xiang AO,Xiaobo ZHU 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1

Low efficiency is an urgent problem to be solved for vortex pumps due to large number of vortices and backflows. This paper concentrates on the performance improvement of vortex pumps caused by changing the indent distance of the impeller. First, a complete numerical model was established by selecting the optimal length of inlet and outlet and appropriate mesh quantity. Then, the reliability of this model was validated by comparing simulation results with experimental data. Based on this model, the internal flows of vortex pumps with different impeller indent distances were observed in simulations and the fitted curves of head and efficiency were created. Finally, the cause of the performance improvement was demonstrated by analyzing the flow field in vortex pumps.

A novel recyclable nano-adsorbent for enhanced oil recovery with efficient removal of Ca2+ and Cr6+ from oilfield wastewater

Lei He,Yong Dai,Zhe Wang,Lutao Yang,Luxia Zhang,Pengpeng Hu,Yutian Lei,Hong Mo,Haomiao Zhu,Jun Zhang 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.8

Oilfield wastewater has a significantly negative influence on the recovery efficiency due to its hypersalinity. Therefore, magnetic graphene oxide (GO) modified with ethylene diamine tetraacetic acid (EDTA) and grafted bypolyethylene glycol (PEG) nano-adsorbent was prepared to remove the Ca2+ and Cr6+ in Jidong Oilfield wastewaterspecifically. It was noteworthy that PEG-g-EDTA/Fe3O4/GO nano-adsorbent had excellent adsorption performance,with removal ratios up to 71.6% for Ca2+ and 42.7% for Cr6+ at 30 min. After the fifth recycling run, the nano-adsorbentstill remained with high removal ratios (69.3% for Ca2+ and 30.5% for Cr6+) and high reuse rates (89.4% for Ca2+and 95.2% for Cr6+), indicating that the nano-adsorbent had outstanding adsorption-desorption efficacy and high reusability. The adsorption test results demonstrated that the total salinity of the treated oilfield wastewater decreased byabout 5,000 ppm, and the displacement efficiency further increased by 12.5% by chemical flooding compared with theuntreated wastewater. Therefore, PEG-g-EDTA/Fe3O4/GO nano-adsorbent is an adsorbent with excellent potentialwhich can effectively remove Ca2+ and Cr6+ in oilfield wastewater to enhance oil recovery (EOR).

Research on Large‑scale Photovoltaic Planning Based on Risk Assessment in Distribution Network

Lei Wang,Minyu Yuan,Fan Zhang,Xuli Wang,Jing Ma,Lei Dai,Xianjun Qi,Rui Bi 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.3

Risks caused by large amounts of distributed photovoltaic (PV) feeding into distribution networks, have an impact on PV planning, which has become a critical consideration for distribution networks’ operation. In this paper, a large-scale PV planning method is proposed which based on risk assessment in distribution networks. Cluster division is used to group large-scale distributed PVs. A risk assessment is performed on the distribution network, considering the correlation between PVs and loads. The efects of load fuctuations, PV quantity, capacity and location on the operational risk of the distribution network are analyzed and discussed. A large-scale PV planning model is established with the goal of maximizing the comprehensive benefts, considering the penalty cost of node voltage over-limit and branch power fow over-limit risk. Finally, the genetic algorithm is used to solve the planning model. The simulation results demonstrate the efectiveness of the proposed method.

Improved Work Function of Preferentially Oriented Indium Oxide Films Induced by the Plasma Exposure Technique

Lei Yang,Shuai Guo,Qiuling Yang,Yuankun Zhu,Bing Dai,Hailing Yu,Pei Lei,Jiecai Han,Ying Hou,Jiaqi Zhu 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.6

The preferentially oriented In2O3 thin films were prepared on glass substrates by conventional magnetron sputtering with Ar+ plasma exposure at room temperature. Based on the x-ray diffraction, x-ray photoelectron spectroscopy, and UV photoelectron spectroscopy results, it was found that the Ar+ plasma exposure not only enhanced the low-temperature crystallization of In2O3 thin films, but also led to a dramatic improvement in the work function. Furthermore, it demonstrated that the shift mechanism of the work function in In2O3 thin films mainly combined with theelimination of oxygen defects and the change of the preferential orientation of In2O3 film surface.

Influence of TOCNs on the PVA/WPU Electrospun Nanofibers

Lei Dai,Zhu Long,Jie Chen,Jianhua Wang,Fengshan Zhang,Jingpeng Zhou,Meiyan Wu 한국펄프·종이공학회 2016 한국펄프·종이공학회 학술발표논문집 Vol.2016 No.10

Effect of Vanadium on the Microstructure and Mechanical Properties of 2100 MPa Ultra-High Strength High Plasticity Spring Steel Processed by a Novel Online Rapid-Induction Heat Treatment

Qi‑Lei Dai,Kun Li,Kai‑Ren Meng,Zhou Fang,Wen Chen,Tian‑Bao Yang,Chi Feng,Jin‑Ming Wu,R. D. K. Misra 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.4

Advanced automotive industries generate large demand for the next generation of high strength and high toughness springsteels. Vanadium-containing 55SiCrV spring steels subjected to rapid-induction heating treatment can fulfil such requirements. However, the effect of vanadium microalloying under online rapid-induction heat treatments is rarely reported. Acomparative study of the microstructure and tensile properties of 55SiCr and 55SiCrV spring steel wires subjected to a novelonline rapid induction heat treatment has been demonstrated herein. It is found that the tensile strength of the 55SiCr springwire decreases with the decrease in the wire speed in online rapid-induction heating, and the plasticity increases. Whereas,the tensile strength of the 55SiCrV steel wire increases with the decrease in the wire speed with the retained high plasticity,which is attributed to the strengthening effect of the dislocations. Through the optimized rapid-induction heating/coolingthermal cycles and intermediate-temperature tempering treatment, the tensile strength of the 55SiCrV steel wire approaches2106 MPa with total elongation of 9.7%. Compared with the 55SiCr spring steel, the addition of V in 55SiCrV spring steelchanges the strengthening and toughening mechanisms via the grain refinement and enhancement in the hardenability andtempering resistance. The finely dispersed V-containing secondary phases are rarely found in the matrix, which indicates thatthe precipitation effect stemming from the addition of V is not the dominant strengthening factor in the online rapid-inductionheat process. The proposed novel online rapid-induction heat treatment provides a promising pathway for the mechanicalproperty improvement of the spring steel.

Antioxidant Properties of Proanthocyanidins Attenuate Carbon Tetrachloride (CCl4)–Induced Steatosis and Liver Injury in Rats via CYP2E1 Regulation

Ning Dai,Yuan Zou,Lei Zhu,Hui-Fang Wang,Mu-Gen Dai 한국식품영양과학회 2014 Journal of medicinal food Vol.17 No.6

Liver steatosis is characterized by lipid dysregulation and fat accumulation in the liver and can lead tooxidative stress in liver. Since proanthocyanidins are present in plant-based foods and have powerful antioxidant properties,we investigated whether proanthocyanidins can prevent oxidative stress and subsequent liver injury. Carbon tetrachloride(CCl4) treatment can cause steatosis in rats that models both alcoholic and non-alcoholic fatty liver disease in humans. Wepre-treated rats by oral administration of proanthocyanidins extracted from grape seeds 7 days prior to intragastricallyadministering CCl4. Proanthocyanidin treatment continued for an additional 2 weeks, after which time liver and serum were harvested, and mediators of liver injury, oxidative stress, and histological features were evaluated. CCl4-treated rats exhibited significant increases in the following parameters as compared to non-treated rats: fat droplets in the liver, liver injury (ALT, AST), and DNA damage (8-OHdG). Additionally, CCl4 treatment decreased antioxidant enzymes SOD, GSH, GPX, and CAT in the liver due to their rapid depletion after battling against oxidative stress. Compared to CCl4-treated rats, treatment with proanthocyanidins effectively suppressed lipid accumulation, liver injury, DNA damage, as well as restored antioxidant enzyme levels. Further investigation revealed that proanthocyanidins treatment also inhibited expression of CYP2E1 in liver, which prevented the initial step of generating free radicals from CCl4. The data presented here show that treatment with orally administered proanthocyanidins prevented liver injury in the CCl4-induced steatosis model, likely through exerting antioxidant actions to suppress oxidative stress and inhibiting the free radical–generating CYP2E1 enzyme.

Analysis of Synchronous Rectification Discontinuous PWM for SiC MOSFET Three Phase Inverters

Dai, Peng,Shi, Congcong,Zhang, Lei,Zhang, Jiahang The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

Wide band gap semiconductor devices such as SiC MOSFETs are becoming the preferred devices for high frequency and high power density converters due to their excellent performances. However, the proportion of the switching loss that accounts for the whole inverter loss is growing along with an increase of the switching frequency. In view of the third quadrant working characteristics of a SiC MOSFET, synchronous rectification discontinuous pulse-width modulation is proposed (SRDPWM) to further reduce system losses. The SRDPWM has been analyzed in detail. Based on a frequency domain mathematical model, a quantitative mathematical analysis of the harmonic characteristic is conducted by double Fourier transform. Meanwhile, a switching loss model and a conduction loss model of inverter for SRDPWM have been built. Simulation and experimental results verify the result of the harmonic analysis of the double Fourier analysis and the accuracy of the loss models. The efficiencies of the SRDPWM and the SVPWM are compared. The result indicates that the SRDPWM has fewer losses and a higher efficiency than the SVPWM under high switching frequency and light load conditions as a result of the reduced number of switching transitions. In addition, the SRDPWM is more suitable for SiC MOSFET converters.

Oil from Antarctic krill (Euphausia superba) facilitates bone formation in dexamethasone-treated mice

Lei Mao,Fei Wang,Yuanyuan Li,Yufeng Dai,Yanjun Liu,Jingfeng Wang,Changhu Xue 한국식품과학회 2019 Food Science and Biotechnology Vol.28 No.2

Glucocorticoids are the leading cause of secondaryosteoporosis. In the current study, the in vivoeffects of Antarctic krill (Euphausia superba) oil (AKO) ondexamethasone-treated mice were investigated. Resultsshowed that AKO significantly prevents bone loss, asevidenced by improved bone mineral density, biomechanicalstrength, and cancellous bone microstructure. Fluorescencedouble-labeling of femur showed that AKOinduces new bone formation. Toluidine blue staining ofmarrow cavity indicated that AKO increases the number oftrabecula, and decreases the generation of adipose cells. Runt-related transcription factor 2 (Runx2) and Peroxisomeproliferator-activated receptor c (PPARc) are the switchesfor osteogenic and adipogenic differentiation of bonemarrow mesenchymal stem cells, respectively. AKO significantlypromoted the expression of Runx2 protein, andreduced PPARc expression in bone tissue. Furthermore,AKO increased the mRNA expression of osteogenesis-relatedgenes and decreased the expression of adipogenesisrelatedgenes. In conclusion, AKO improved glucocorticoid-induced osteoporosis via promoting bone formation.

Association of the A-G Polymorphism in Porcine Adiponectin Gene with Fat Deposition and Carcass Traits

Dai, L.H.,Xiong, Y.Z.,Deng, C.Y.,Jiang, S.W.,Zuo, B.,Zheng, R.,Li, F.E.,Lei, M.G. Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.6

The adiponectin gene is known to be involved in the regulation of energy homeostasis involving food intake, carbohydrate and lipid metabolism. Human adiponectin gene polymorphisms have been recently reported to be associated with obesity, insulin sensitivity and the risk of type 2 diabetes. The present study was carried out to investigate the porcine adiponectin gene as a candidate gene for fat deposition and carcass traits. A mutation of A178G of the porcine adiponectin gene that resulted in substitution of the amino acid Isoleucine to Valine was identified. AcyI PCR-RFLP was used to detect the polymorphism of the genotypes in five different pig populations (Large White, Landrace, Duroc, Chinese breeds Meishan and Qingping). The A allele frequency was significantly higher among subjects from Chinsese lard type breeds, while the G allele was the only one present in those from Western lean type breeds. To determine if there was an association of the polymorphism with phenotypic variation, the mutation was tested in 267 pigs of the "Large $White{\times}Meishan$" F2 resource population. The results of association analyses showed significant associations of the genotypes with fat deposition and carcass traits. Allele G was significantly associated with increase in loin eye height, loin eye area and lean meat percentage and bone percentage, and decrease in fat mean percentage, ratio of lean to fat, shoulder fat thickness, 6-7 rib fat thickness, thorax-waist fat thickness and buttock fat thickness. The substitution of A178G (Ile60Val) happened to be located at amino acid 60 in the collagenous domain of porcine adiponectin which might affect the association into higher-order structures, and accordingly affect the posttranslational modifications and optimal biological activity of the multimeric forms. The identified functional polymorphism provides new evidence of adiponectin as an important candidate gene affecting fat deposition and carcass traits in pigs.