Electrochemically Deposited CZTSSe Thin Films for Monolithic Perovskite Tandem Solar Cells with Efficiencies Over 17%

In spite of the high potential economic feasibility of the tandem solar cells consisting of the halide perovskite and the kesterite Cu2ZnSn(S,Se)4(CZTSSe),they have rarely been demonstrated due to the difficulty in implementing solution-processed perovskite top cell on the rough surface of the bottom cells.Here,we firstly demonstrate an efficient monolithic two-terminal perovskite/CZTSSe tandem solar cell by significantly reducing the surface roughness of the electrochemically deposited CZTSSe bottom cell.The surface roughness(R_(rms))of the CZTSSe thin film could be reduced from 424 to 86 nm by using the potentiostatic mode rather than using the conventional galvanostatic mode,which can be further reduced to 22 nm after the subsequent ion-milling process.The perovskite top cell with a bandgap of 1.65 eV could be prepared using a solution process on the flattened CZTSSe bottom cell,resulting in the efficient perovskite/CZTSSe tandem solar cells.After the current matching between two subcells involving the thickness control of the perovskite layer,the best performing tandem device exhibited a high conversion efficiency of 17.5%without the hysteresis effect.

Complications and management of forgotten long-term biliary stents

AIMTo evaluate complications and management outcomes of retained long-term plastic biliary stents.METHODSEndoscopic plastic biliary stent placement was performed in 802 patients at Yeungnam University Hospital between January 2000 and December 2014. Follow-up loss with a subsequently forgotten stent for more than 12 mo occurred in 38 patients. We retrospectively examined the cause of biliary stent insertion, status of stents, complications associated with biliary stents and management outcomes of long-term plastic biliary stents. Continuous variables were analyzed using the t test. Observed frequencies in subsets of the study population were compared using Fisher’s exact test and χ2 tests. Statistical significance was defined as P < 0.05 (two-tailed).RESULTSMean age of patients was 73.7 ± 12 years and male-to-female ratio was 2.2:1. Indications of plastic biliary stent insertion were bile duct stones (63.2%, 24/38) and benign bile duct stricture (52.6%, 20/38). Mean duration of retained plastic stent was 22.6 ± 12.2 mo, and in 10 cases (26.3%), stents were retained for more than 24 mo. Common bile duct (CBD) stones or sludge were found in most cases (92.1%, 35/38). The most common complication was acute cholangitis (94.7%, 36/38). Stent removal by endoscopic approach was successfully performed in 92.1% (35/38) of the cases. In 3 cases, an additional plastic stent was inserted alongside the previous stent due to failure of the stent removal. Endoscopic removal of bile duct stones was successful in 73.7% (28/38) of the cases. When patients were divided into two groups by duration of stent placement (12 to 24 mo vs over 24 mo), there were no differences in the development of cholangitis, presence of biliary stones, and success rate of endoscopic removal of stones and biliary stents.CONCLUSIONThe most common complication of retained long-term plastic biliary stents was acute cholangitis associated with CBD stones. Endoscopic management was successfully performed in most cases.

Prediction of the indication criteria for endoscopic resection of early gastric cancer

AIM: To find risk factors of lymph node metastasis(LNM) in early gastric cancer(EGC) and to find proper endoscopic therapy indication in EGC.METHODS: We retrospectively reviewed the 2270 patients who underwent curative operation for EGC from January 2001 to December 2008. EGC was defined as malignant lesions that do not invade beyond the submucosal layer of the stomach wall irrespective of presence of lymph node metastasis.RESULTS: Among 2270 enrolled patients, LNM was observed in 217(9%) patients. LNM in intramucosal(M) cancer and submucosal(SM) cancer was detectedin 3 8( 2. 8 %, 3 8 / 1 3 4 0) patients and 1 7 9(19%, 179/930) patients, respectively. In univariate analysis, the risk factors for LNM in EGC were size of tumor, Lauren classification, ulcer, lymphatic invasion, vascular invasion, and depth of invasion. However, in multivariate analysis, size of tumor, lymphatic invasion, vascular invasion, and depth of invasion were risk factors for LNM in EGC. Size of tumor, lymphatic invasion, vascular invasion, and depth of invasion were risk factors for LNM in cases of intramucosal cancer and submucosal cancer. In particular, there was no lymph node metastasis in cases of well differentiated early gastric cancer below 1 cm in size without ulcer regardless of lymphovascular invasion.CONCLUSION: Tumor size, perilymphatic-vascular invasion, and depth of invasion were risk factors for LNM in EGC. There was no LNM in EGC below 1 cmregardless risk factors.

Thermal Radiation, Joule Heating, and Viscous Dissipation Effects on MHD Forced Convection Flow with Uniform Surface Temperature

In this paper, we studied the effects of thermal radiation, Joule heating and viscous dissipation on forced convection flow in a magnetohydrodynamics (namely MHD) pump in rectangular channel with uniform surface temperature. Numerical results were obtained by solving the nonlinear governing momentum and energy equations with steady state fully developed assumptions by finite difference method. The Lorentz force in momentum and Joule heating, and viscous dissipation in energy equation with the Rossel and approximation are assumed to increase the knowledge of the details of the temperature and flow field in order to design a MHD pump. The purpose of this study is the parametric study of a Newtonian fluid in a MHD pump. The values of maximum velocity, fully developed Nusselt number for different values of magnetic density flux, Brinkman number, viscous heating and radiation number are obtained. However, the maximum temperature stays almost constant with magnetic field, as current increases, the velocity and the temperature increase too. Besides, the increase of thermal radiation number causes the increase in effective thermal conductivity and decrease in thermal boundary layer and the Nusselt number at wall.

Evaluation of factors affecting the success rate of orthodontic mini-implants by survival analysis

AIM: To investigate the success rate of mini-implants and its characteristics and risk factors by survival analyses. METHODS: Three hundred and ninety-four miniimplants of the same type were placed by a single clinician. Age, gender, treatment duration, time of failure, side and jaw of implantation and the soft tissue at placement site were recorded. Odds ratio, survival curves, and Cox proportional hazard model were applied to evaluate the factors influencing the miniimplants' success rate. RESULTS: The cumulative success rate was 88.1%.The maxilla had a significantly higher success rate than that of the mandible(91.7% vs 83.7%, respectively, P = 0.019). Placement of mini-implants in the attached gingiva(AG) showed a higher success rate than that of the mucogingival junction(MGJ) and mucous membrane(MM)(AG, 94.3%; MGJ, 85.8%; MM, 79.4%; P < 0.001). Significant association was found between the jaw and the gingival tissue type(P < 0.001). There were no significant differences between maxilla and mandible when compared within each placement site.CONCLUSION: The gingival tissue type had the most significant effect on the success rate of the mini-implant with higher success rate in the attached gingiva.

A Study on Development of Balanced Scorecard for Management Evaluation Using Multiple Attribute Decision Making

Recently, most businesses have introduced a system for improving their responsibility to the customers in terms of job improvement. For example, small-quantity batch production increases cost but improve efficiency of management. Companies have been introduced the balanced scorecard to evaluate their management as part of improvement, while they suffer from many trials and errors. Many businesses still have difficulty in introducing balance scorecard concept in their process, but we suggest a method to successfully introduce the balance scorecard. This study aims to suggest a new performance measurement model reflecting relative importance of the key performance indicators for each factor. Our model is applied to several companies in real-world to validate the new model. Also, our study proposes a methodology for an adequate performance measurement using multiple attribute decision making.

Effect of molybdenum on interfacial properties of titanium carbide reinforced Fe composite

This study shows that the mechanical strength of the composite of Fe matrix and titanium carbide(Ti C)ceramic particles is significantly enhanced with addition of molybdenum(Mo) atoms. Ti C reinforced Fe(Fe-0.2C-7Mn) composites with and without Mo were fabricated by a liquid pressing infiltration(LPI)process and the effect of Mo on interfacial properties of TiC–Fe composite was investigated using atomic probe tomography(APT) analysis, molecular dynamics(MD) simulations, first-principle density functional theory(DFT), and thermodynamic calculations. First, DFT calculations showed that total energies of the Mo-doped Ti C–Fe superlattices strongly depend on the position of Mo defects, and are minimized when the Mo atom is located at the TiC/Fe interface, supporting the probable formation of MoC-like interphase at the TiC/Fe interface region. Then, APT analysis confirmed the DFT predictions by finding that about6.5 wt.% Mo is incorporated in the Ti C–Fe(Mo) composite and that sub-micrometer thick(Ti,Mo)C interphase is indeed formed near the interface. The MD simulations show that Mo atoms migrate to the Mo-free TiC–Fe interface at elevated temperatures and the mechanical strength of the interface is considerably enhanced, which is in good agreement with experimental observations.