Efficient fluorescent white organic light-emitting devices with a reduced efficiency roll-off based on a blue ambipolar fluorescent emitter

Tianyu Zhang,Tong Li,Wei Hu,Weiqi Wang,Letian Zhang,Wenfa Xie 한국물리학회 2014 Current Applied Physics Vol.14 No.5

White organic light-emitting devices (WOLEDs) with fluorescent donor-acceptor-substituted spirobifluorene compounds (red 2-diphenylamino-7-(2,2-dicyanovinyl)-9,90-spirobifluorene and blue 2- diphenylamino-7-(2,2-diphenylvinyl)-9,90-spirobifluorene) have been fabricated. The optimized WOLEDs shows a maximum current efficiency 5.9 cd/A and very low efficiency roll-off. From the brightness at maximum current efficiency to high brightness of 10000 cd/m2, the current efficiency rolloff is only 0.4%. It can be attributed to the ambipolar blue fluorescent emitter with voltage-independnet mobility which makes the device having a broader charge recombination zone and balance of carrier transport.

Heart Failure Is Associated with Increased Risk of Long-Term Venous Thromboembolism

Tianyu Xu,Yuli Huang,Zuheng Liu,Yujia Bai,Zhuang Ma,Xiaoyan Cai,Yuhui Zhang,Jian Zhang 대한심장학회 2021 Korean Circulation Journal Vol.51 No.9

Background and Objectives: Venous thromboembolism (VTE), consisting of deep vein thrombosis (DVT) and pulmonary embolism (PE), is highly prevalent in in-hospital HF patients and contributes to worse prognoses. However, the risk of VTE in out-patients with HF in long-term period is controversial. This study aimed to evaluate the associations between HF and the risk of VTE in a long-term follow-up duration. Methods: We searched for studies investigating the risk of VTE, PE, and DVT in patients with HF before April 15, 2020, in PubMed, MEDLINE, and Embase databases. Cohort studies and post hoc analysis of RCTs were eligible for inclusion if they reported relative risk of VTE, DVT or PE in patients with HF in more than 3-month follow-up period. Results: We identified 31 studies that enrolled over 530,641 HF patients. Overall, patients with HF were associated with an increased risk of VTE (risk ratio [RR]=1.57, 95% confidence interval [CI]=1.34–1.84) and PE (RR=2.00, 95% CI=1.38–2.89). However, the risk of DVT was not significantly increased in HF patients (RR=1.33, 95% CI=0.67–2.63). Subgroup analysis showed that patients with chronic HF (RR=1.54, 95% CI=1.32–1.80) had a higher risk of VTE than those with acute HF (RR=0.95, 95% CI=0.68–1.32). Conclusions: In conclusion, HF was an independent risk for VTE and PE but not DVT in a long-term follow-up period. Patients with chronic HF were prone to suffer from VTE than acute HF.

Long Non-coding RNA CASC15 Promotes Intrahepatic Cholangiocarcinoma Possibly through Inducing PRDX2/PI3K/AKT Axis

Yuan Zhang,Lufei Zhang,Sinan Lu,Yucheng Xiang,Cheng Zeng,Tianyu He,Yuan Ding,Weilin Wang 대한암학회 2021 Cancer Research and Treatment Vol.53 No.1

Purpose Intrahepatic cholangiocarcinoma (ICC) is one of the most common liver primary tumors but its treatments are limited. Bioinformatics showed that the expression level of long non-coding RNA cancer-associated susceptibility 15 gene (CASC15) is correlated with ICC progression, but its functional mechanism remains unclear. Materials and Methods Tissues from ICC patients, tumor and adjacent tissue, were used for detection of the expression of CASC15. Clinical data were also collected for clinicopathologic and survival analysis. Short interfering RNA and lentiviral short hairpin RNA were used to knock down CASC15 and PRDX2 expression in ICC cell lines, for the analysis of changes of cell function and xenografts. RNA-pulldown and RNA immunoprecipitation assays were used to detect RNA-binding protein, PRDX2. Male nude mice were used for ICC xenografts, and livers were collected after 4 weeks for immunohistochemistry. Results CASC15 is highly expressed in ICC tissues and is related to higher TNM stage. Knockdown of CASC15 in ICC cells reduced cell proliferation, migration, invasiveness and increased apoptosis, and G1/S block. PRDX2 bound to CASC15. Knockdown of CASC15 decreased PRDX2 expression which was rescued by the inhibition of proteasome formation. Downregulation of PRDX2 resulted in G1/S block, reduced ICC cell invasion. Downregulation of CASC15 inhibited phosphoinositide 3-kinase (PI3K)/AKT/c-Myc pathway through downregulating of PRDX2 and overexpressed PRDX2 rescued the block. CASC15 knockout in ICC xenografts suppressed tumor development in vivo, decreased the expression of PRDX2 and Ki67 and inhibited PI3K/AKT pathway. Conclusion CASC15 promotes ICC possibly by targeting PRDX2 via the PI3K/AKT pathway, indicating poor prognosis and high degree of malignancy of ICC.

Damping for Wind Turbine Electrically Excited Synchronous Generators

Tianyu, Wang,Guojie, Li,Yu, Zhang,Chen, Fang The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.4

The electrically excited synchronous generator (EESG) is applied in wind turbine systems recently. In an EESG control system, electrical torque is affected by stator flux and rotor current. So the control system is more complicated than that of the permanent-magnet synchronous generator (PMSG). Thus, the higher demanding of the control system is required especially in case of wind turbine mechanical resonance. In this paper, the mechanism of rotor speed resonant phenomenon is introduced from the viewpoint of mechanics firstly, and the characteristics of an effective damping torque are illustrated through system eigenvalues analysis. Considering the variables are tightly coupled, the four-order small signal equation for torque is derived considering stator and rotor control systems with regulators, and the bode plot of the closed loop transfer function is analyzed. According to the four-order mathematical equation, the stator flux, stator current, and electrical torque responses are derived by torque reference step and ramp in MATLAB from a pure mathematical deduction, which is identical with the responses in PSCAD/EMTDC simulation results. At last, the simulation studies are carried out in PSCAD software package to verify the resonant damping control strategy used in the EESG wind turbine system.

Histological Validation of Cardiovascular Magnetic Resonance T1 Mapping for Assessing the Evolution of Myocardial Injury in Myocardial Infarction: An Experimental Study

Zhang Lu,Yang Zhi-gang,Xu Huayan,Yang Meng-xi,Xu Rong,Chen Lin,Sun Ran,Miao Tianyu,Zhao Jichun,Zhou Xiaoyue,Fu Chuan,Guo Yingkun 대한영상의학회 2020 Korean Journal of Radiology Vol.21 No.12

Objective: To determine whether T1 mapping could monitor the dynamic changes of injury in myocardial infarction (MI) and be histologically validated. Materials and Methods: In 22 pigs, MI was induced by ligating the left anterior descending artery and they underwent serial cardiovascular magnetic resonance examinations with modified Look-Locker inversion T1 mapping and extracellular volume (ECV) computation in acute (within 24 hours, n = 22), subacute (7 days, n = 13), and chronic (3 months, n = 7) phases of MI. Masson’s trichrome staining was performed for histological ECV calculation. Myocardial native T1 and ECV were obtained by region of interest measurement in infarcted, peri-infarct, and remote myocardium. Results: Native T1 and ECV in peri-infarct myocardium differed from remote myocardium in acute (1181 ± 62 ms vs. 1113 ± 64 ms, p = 0.002; 24 ± 4% vs. 19 ± 4%, p = 0.031) and subacute phases (1264 ± 41 ms vs. 1171 ± 56 ms, p < 0.001; 27 ± 4% vs. 22 ± 2%, p = 0.009) but not in chronic phase (1157 ± 57 ms vs. 1120 ± 54 ms, p = 0.934; 23 ± 2% vs. 20 ± 1%, p = 0.109). From acute to chronic MI, infarcted native T1 peaked in subacute phase (1275 ± 63 ms vs. 1637 ± 123 ms vs. 1471 ± 98 ms, p < 0.001), while ECV progressively increased with time (35 ± 7% vs. 46 ± 6% vs. 52 ± 4%, p < 0.001). Native T1 correlated well with histological findings (R2 = 0.65 to 0.89, all p < 0.001) so did ECV (R2 = 0.73 to 0.94, all p < 0.001). Conclusion: T1 mapping allows the quantitative assessment of injury in MI and the noninvasive monitoring of tissue injury evolution, which correlates well with histological findings.

Study on localization influences of frequency veering on vibration of mistuned bladed disk

Hongyuan Zhang,Huiqun Yuan,Wenjun Yang,Tianyu Zhao 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

Reduced-order models of the bladed disk of the aero-engine compressor were established by adopting Prestressed component mode synthesis (PCMS) method. The frequency veering characteristics of the tuned bladed disk were analyzed. From the aspect of the strain energy, the forced vibration response of the mistuned bladed disk was analyzed, along with calculation of the contribution degree factors, the localization factors and frequency veering distances, finding the influences of the frequency veering distance, the contribution degree factors and the localization. The results show that frequency veering has significant influence on vibration localization of the mistuned bladed disk; in the region of frequency veering, the degree of vibration localization of the mistuned bladed disk is relatively high; along with the changes of the frequency veering distance, the contribution degree of the strain energy of the blades of localization of the mistuned bladed disk shows the certainty of regularity.

Damping for Wind Turbine Electrically Excited Synchronous Generators

Wang Tianyu,Li Guojie,Zhang Yu,Fang Chen 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.4

The electrically excited synchronous generator (EESG) is applied in wind turbine systems recently. In an EESG control system, electrical torque is affected by stator flux and rotor current. So the control system is more complicated than that of the permanent-magnet synchronous generator (PMSG). Thus, the higher demanding of the control system is required especially in case of wind turbine mechanical resonance. In this paper, the mechanism of rotor speed resonant phenomenon is introduced from the viewpoint of mechanics firstly, and the characteristics of an effective damping torque are illustrated through system eigenvalues analysis. Considering the variables are tightly coupled, the four-order small signal equation for torque is derived considering stator and rotor control systems with regulators, and the bode plot of the closed loop transfer function is analyzed. According to the four-order mathematical equation, the stator flux, stator current, and electrical torque responses are derived by torque reference step and ramp in MATLAB from a pure mathematical deduction, which is identical with the responses in PSCAD/EMTDC simulation results. At last, the simulation studies are carried out in PSCAD software package to verify the resonant damping control strategy used in the EESG wind turbine system.

Shear-lag behavior of prestressed concrete box-girder bridges during balanced cantilever construction

Zhong, Xingu,Zhang, Tianyu,Shu, Xiaojuan,Xu, Hongliang Techno-Press 2017 Advances in concrete construction Vol.5 No.5

Balanced cantilever construction is extensively used in the construction of prestressed concrete (PSC) box-girder bridges. Shear-lag effect is usually considered in finished bridges, while the cumulative shear-lag effect in bridges during balanced cantilever construction is considered only rarely. In this paper, based on the balanced cantilever construction sequences of large-span PSC box-girder bridges, the difference method is employed to analyze the cumulative shear-lag effect of box girders with varying depth under the concrete segments' own weight. During cantilever construction, no negative shear-lag effect is generated, and the cumulative shear-lag effect under the balanced construction procedure is greater than the instantaneous shear-lag effect in which the full dead weight is applied to the entire cantilever. Three cross-sections of Jianjiang Bridge were chosen for the experimental observation of shear-lag effect, and the experimental results are in keeping with the theoretical results of cumulative shear-lag effect. The research indicates that only calculating the instantaneous shear-lag effect is not sufficiently safe for practical engineering purposes.

Simultaneous Impact of Multiple Droplets on Liquid Film

Gangtao Liang,Tianyu Zhang,Haibing Yu,Hongliang Chen,Shengqiang Shen 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.65 No.-

Multiple droplets impinging on a thin liquid film simultaneously is numerically studied using a three-dimensional model with an implement of a random disturbance subjected to Gaussian distribution. This model is very effective to predict droplet splashing under relatively high impingement momentum. Interface evolutions and field distributions are addressed after droplets impact. Besides, a geometric model is built up to demarcate the impact region into two semicircular regions and a series of rectangular regions during simultaneous impact, further to discuss the variations of area and residual film thickness in each region as well as the total area and average film thickness.

Seismic Performance of a Subway Station-Tunnel Junction Structure: A Shaking Table Investigation and Numerical Analysis

Qingjun Chen,Tianyu Zhang,Na Hong,Bin Huang 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.5

Damage cases show that during earthquakes, the sharp stiffness mutation of subway station-tunnel junction structures can lead to dislocations at the connections. To address this, shaking table tests were conducted followed by numerical simulations of a typical junction structure with rigid connections. The modeling method was verified based on the test results. Furthermore, numerical models of junction structures with rigid and flexible connections, single stations, and single tunnels were built, and deformation modes and stress distributions were comparatively analyzed. Combining the experimental and numerical results, it is found that there exists an intensive deformation inconsistency between the stations and the tunnels responsible for the junction structures’ dislocation failures. The station operates in both racking and distortion deformation modes when the tunnel undergoes ovaling deformation. The tunnel bends relative to the end wall at the connection. The junction structure with rigid connections is most at risk at the point located at the tunnel section connected to the end wall and near the bottom plate-sidewall joint. With flexible connections, the tunnels integrally translate relative to the end wall, and the stress response of the end wall openings can be larger than those with rigid connections.