The interface and its role in carrier transfer/recombination dynamics for the planar perovskite solar cells prepared under fully open air conditions

Fei Wang,Yiqing Chen,Guotao Han,Qianlong Zhang,Qilin Ma 한국물리학회 2016 Current Applied Physics Vol.16 No.10

The planar heterojunction perovskite solar cells, where the perovskite film is deposited directly onto a flat hole blocking layer, have recently attracted a great deal of attention owing to their high performance and ease of processing. However, the interface and its underlying role in carrier transport/recombination kinetics for such perovskite devices prepared under ambient air is still obscure. Herein, we addressed this issue by a dynamic intensity modulated photovoltage spectroscopy (IMVS) model using a continuity equation. The interface and its role in charge-carrier transport/recombination kinetics have been explored and discussed as an approach to understand the origin of the photovoltaic properties for the devices prepared under ambient air. The experimental IMVS responses were measured and satisfactorily fitted to the analytical results. Compared to the typical IMVS model based on dye-sensitized solar cells (DSSCs), the better IMVS fitting results presented in this study indicated that there was a discrepancy between the planar perovskite devices and those of DSSCs in electron transport/recombination properties, because carrier transfer across the TiO2/liquid electrolyte interface in DSSCs has been modified. That is, the Schottky interface in DSSCs needs to be replaced by the semiconductor heterojunction interface in perovskite solar cells (PSCs). Besides, the interface exhibits a more significant role in determining the carrier transport/recombination process by influencing the boundary conditions in a continuity equation. Furthermore, the intensity modulated photocurrent/photovoltage spectroscopy responses demonstrated that the carrier recombination characteristic is ultimately related with the surface and defect density in the interface. Interfacial modification, such as air-annealing, resulting in crystallographic changes, oxygen passivation, and variation in grain domain size, could suppress carrier recombination and prolong charge lifetime, which can yield more photo-generated electrons to be collected by anode, subsequently resulting in strikingly improving photovoltaic performance of the devices. In short, the dynamic IMVS model would help in elucidating the role of interface and the importance of interfacial modification or even interface design in order to obtain a highly efficient solar cell. The study can not only pave the way to construct the currentvoltage curve using a continuity equation model, but also provide new insights into the performance-improving steps for the PSCs prepared under fully open air conditions, which is of great importance for their future commercialization.

MIXED BOUNDARY VALUE PROBLEMS FOR SECOND ORDER DIFFERENTIAL EQUATIONS WITH DIFFERENT DEVIATED ARGUMENTS

Zhang, Lihong,Wang, Guotao,Song, Guangxing The Korean Society for Computational and Applied M 2011 Journal of applied mathematics & informatics Vol.29 No.1

This paper deals with second order differential equations with different deviated arguments ${\alpha}$(t) and ${\beta}$(t, ${\mu}$(t)). We investigate the existence of solutions of such problems with nonlinear mixed boundary conditions. To obtain corresponding results we apply the monotone iterative technique and the lower-upper solutions method. Two examples demonstrate the application of our results.

Mixed boundary value problems for second order differential equations with different deviated arguments

Lihong Zhang,Guotao Wang,Guangxing Song 한국전산응용수학회 2011 Journal of applied mathematics & informatics Vol.29 No.1

This paper deals with second order differential equations with different deviated arguments α(t) and β(t, μ(t)). We investigate the existence of solutions of such problems with nonlinear mixed boundary conditions. To obtain corresponding results we apply the monotone iterative technique and the lower-upper solutions method. Two examples demonstrate the application of our results.

Permeability Anisotropy of Columnar Jointed Rock Masses

Lifang Zou,Weiya Xu,Guotao Meng,Yu Ning,Huanling Wang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10

This paper investigated the anisotropic permeability of columnar jointed rock masses at Baihetan hydropower station in Southwest China. Discrete element analysis is conducted to evaluate the hydraulic Representative Elemental Volume (REV) size of jointed rock masses. It is found to be 5m×5m and it is seven times of the column length. Research shows that permeability tensor of the jointed rocks exists. The maximum principle permeability is 3.47 × 10−14 m2 and the minimum principle permeability is 1.39 × 10−14 m2. The direction of maximum principle permeability is 72 degrees anticlockwise from the positive x- axis direction, which is along the same direction of the column length. A continuum hydro-mechanical coupling analysis is carried out on water infill of a tailrace tunnel in columnar basalt. An equivalent anisotropic mechanical model is applied in the numerical simulation. Anisotropic deformation and anisotropic permeability characteristics are investigated under the condition that the angle between maximum principle stress axis and maximum principle permeability axis is 72 degrees. Results show that anisotropic seepage field has an effort on anisotropic deformation field.

Strain rate effect of steel-concrete composite panel indented by a hemispherical rigid body

Weiyi Zhao,Lin Wang,Guotao Yang,Ziguo Wang,Zepeng Gao,Quanquan Guo 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.6

This paper presents numerical and theoretical investigations on the strain rate in steel-concrete composite (SC) panels under low-velocity impact of a hemispherical rigid body. Finite element analyses were performed on five specimens with different loading rates. The impact energy was kept constant to eliminate its influence by simultaneously altering the velocity and mass of the projectile. Results show that the strain rate in most parts of the specimens was low and its influence on bearing capacity and energy dissipation was limited in an average sense of space and time. Therefore, the strain rate effect can be ignored for the analyses of global deformation. However, the strain rate effect should be considered in local contact problems. Equations of the local strain and strain rate were theoretically derived.

Study on Semi-Solid A380 Aluminum Alloy Slurry Prepared by Water-Cooling Serpentine Channel and Its Rheo-Diecasting

Zhiyong Liu,Weimin Mao,Tan Wan,Guotao Cui,Weipan Wang 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

The semi-solid A380 aluminum alloy slurry prepared by water-cooling serpentine channel and its rheo-diecasting werestudied in this paper. The result showed that the pouring temperature and cooling water fow rate had a signifcant efect onthe semi-solid slurry. When the pouring temperature decreased from 670 to 610 °C, the average grain diameter and shapefactor of the primary α-Al grains decreased from 64 to 47 µm and increased from 0.74 to 0.82, respectively, but the mass ofsemi-solid slurry blocked in channel increased. With the cooling water fow rate increasing from 0 to 1000 L/h, the semisolid slurry frstly got optimized and then deteriorated. Under the condition of the same die casting process parameters, therheo-diecastings produced by the semi-solid slurry prepared through water-cooled serpentine channel had higher mechanicalproperties than those of the traditional die castings.

Image formulas and graphical interpretation of fractional derivatives of R-function and G-function

Mehar Chand,Praveen Agarwal,Shilpi Jain,Guotao Wang,K.S. NISAR 장전수학회 2016 Advanced Studies in Contemporary Mathematics Vol.26 No.4

In this paper, our main objective is to establish certain new image formulas of R- and G-functions by applying the operators of fractional derivative involving Appell's function F3(.) due to Saigo-Maeda and the main results interpreted graphically by implementing the MatLab(R2012a). Furthermore, by employing some integral transforms on the resulting formulas, we presented some more image formulas. All the results derived here are of general character and can yield a number of (known and new) results in the theory of special functions.

Simple fabrication of N-doped mesoporous TiO ₂ nanorods with the enhanced visible light photocatalytic activity

Zhou, Xiufeng,Lu, Juan,Jiang, Jingjing,Li, Xiaobin,Lu, Mengna,Yuan, Guotao,Wang, Zuoshan,Zheng, Min,Seo, Hyo Jin Springer 2014 NANOSCALE RESEARCH LETTERS Vol.9 No.1

<P>N-doped mesoporous TiO<SUB>2</SUB> nanorods were fabricated by a modified and facile sol–gel approach without any templates. Ammonium nitrate was used as a raw source of N dopants, which could produce a lot of gasses such as N<SUB>2</SUB>, NO<SUB>2</SUB>, and H<SUB>2</SUB>O in the process of heating samples. These gasses were proved to be vitally important to form the special mesoporous structure. The samples were characterized by the powder X-ray diffraction, X-ray photoelectron spectrometer, nitrogen adsorption isotherms, scanning electron microscopy, transmission electron microscopy, and UV-visible absorption spectra. The average length and the cross section diameter of the as-prepared samples were <I>ca</I>. 1.5 μm and ca. 80 nm, respectively. The photocatalytic activity was evaluated by photodegradation of methylene blue (MB) in aqueous solution. The N-doped mesoporous TiO<SUB>2</SUB> nanorods showed an excellent photocatalytic activity, which may be attributed to the enlarged surface area (106.4 m<SUP>2</SUP> g<SUP>-1</SUP>) and the narrowed band gap (2.05 eV). Besides, the rod-like photocatalyst was found to be easy to recycle.</P>

Two-Dimensional Shear Wave Elastography Predicts Liver Fibrosis in Jaundiced Infants with Suspected Biliary Atresia: A Prospective Study

Chen Huadong,Zhou Luyao,Liao Bing,Cao Qinghua,Jiang Hong,Zhou Wenying,Wang Guotao,Xie Xiaoyan 대한영상의학회 2021 Korean Journal of Radiology Vol.22 No.6

Objective: This study aimed to evaluate the role of preoperative two-dimensional (2D) shear wave elastography (SWE) in assessing the stages of liver fibrosis in patients with suspected biliary atresia (BA) and compared its diagnostic performance with those of serum fibrosis biomarkers. Materials and Methods: This study was approved by the ethical committee, and written informed parental consent was obtained. Two hundred and sixteen patients were prospectively enrolled between January 2012 and October 2018. The 2D SWE measurements of 69 patients have been previously reported. 2D SWE measurements, serum fibrosis biomarkers, including fibrotic markers and biochemical test results, and liver histology parameters were obtained. 2D SWE values, serum biomarkers including, aspartate aminotransferase to platelet ratio index (APRi), and other serum fibrotic markers were correlated with the stages of liver fibrosis by METAVIR. Receiver operating characteristic (ROC) curves and area under the ROC (AUROC) curve analyses were used. Results: The correlation coefficient of 2D SWE value in correlation with the stages of liver fibrosis was 0.789 (p < 0.001). The cut-off values of 2D SWE were calculated as 9.1 kPa for F1, 11.6 kPa for F2, 13.0 kPa for F3, and 15.7 kPa for F4. The AUROCs of 2D SWE in the determination of the stages of liver fibrosis ranged from 0.869 to 0.941. The sensitivity and negative predictive value of 2D SWE in the diagnosis of ≥ F3 was 93.4% and 96.0%, respectively. The diagnostic performance of 2D SWE was superior to that of APRi and other serum fibrotic markers in predicting severe fibrosis and cirrhosis (all p < 0.005) and other serum biomarkers. Multivariate analysis showed that the 2D SWE value was the only statistically significant parameter for predicting liver fibrosis. Conclusion: 2D SWE is a more effective non-invasive tool for predicting the stage of liver fibrosis in patients with suspected BA, compared with serum fibrosis biomarkers.

Sciatic nerve leachate of cattle causes neuronal differentiation of PC12 cells via ERK1/2 signaling pathway

Ziqiang Zhang,Yumei Liu,Xuemin Zhu,Lan Wei,Jiamin Zhu,Ke Shi,Guotao Wang,Li Pan 대한수의학회 2018 Journal of Veterinary Science Vol.19 No.4

Previous studies have shown that the sciatic nerve has neurotrophic activity, and nerve regeneration, differentiation, and axon outgrowth can be modulated by different sciatic nerve preparations. However, numerous animals may have to be sacrificed to obtain enough sciatic nerves to make a sciatic nerve preparation. Some studies have demonstrated that the role of sciatic nerve preparations in neural differentiation depends on the neurotrophins that Schwann cells secrete, and these factors are highly conserved among different species. To reduce the use of experimental animals, in this study, we made a leachate by using the sciatic nerve of cattle and explored its effect on neuronal differentiation of rat PC12 cells (a useful model for studying neuronal differentiation). Results showed the neurite outgrowth of PC12 cells treated with the cattle sciatic nerve leachate for 3, 6, and 9 days was significantly improved, and the expressions of β3-tubulin and microtubule-associated protein 2 (two neuron-specific proteins) were increased. Moreover, the ERK1/2 signaling pathway was activated after PC12 cells were incubated with cattle sciatic nerve leachate for 9 days. Thus, a sciatic nerve leachate obtained from cattle can effectively induce neuronal differentiation of rat PC12 cells via ERK1/2 signaling pathway.