Effect of teeth bending and mushrooming damages on leakage performance of a labyrinth seal

Xin Yan,Xinbo Dai,Kang Zhang,Jun Li,Kun He 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.10

To achieve higher aerodynamic performance, turbine usually works at tight clearance, which results in inevitable rub between the rotor and stator parts of labyrinth seal due to vibrations, misalignment, mechanical force, thermal stress, etc. In the rubbing events, contact between labyrinth fin and rotor part will commonly induce the teeth bending and mushrooming damages, which significantly affect the discharge performance of a labyrinth seal. To account for the influence of teeth bending and mushrooming on leakage performance of a straight-through labyrinth seal, the leakage rates and flow fields in the worn labyrinth seal are measured and also compared with the original design cases. With numerical methods, the discharge behaviors of the labyrinth seal with different degrees of bending and mushroom damages are analyzed. It shows that the predicted leakage performance and flow fields in the labyrinth seals match well with the experimental tests. For the bending cases, the leakage rates and flow patterns in labyrinth seals are dependent on the effective clearance and bending angle. The leakage ratio of forward bending case is smaller than that of backward bending case with the same geometrical dimensions. However, for the mushroomed labyrinth seals, the leakage rates and flow patterns are much dependent on the effective clearance but slightly dependent on the mushroom radius.

Reduction of heat transfer and improvement of film cooling effect on squealer tip with multi-rib design concept

Xin Yan,Jinxing Yu,Mingliang Ye,Kun He 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

A multi-rib design concept was proposed to reduce the heat transfer and enhance film cooling effect on squealer tip. Three different shapes of ribs (i.e. straight ribs, Vshape ribs, and L-shape ribs) were configured in the cavity of squealer tip of a turbine stage. The distributions of heat transfer coefficient (HTC) and film cooling effectiveness (FCE) on the multi-rib squealer tip were numerically predicted and compared against the conventional squealer tip. The results indicate that the configuration of multiple ribs is beneficial to weaken the development of cavity vortex system, and also traps more coolants in the squealer cavity. Compared to the conventional design, the implementation of L-shape ribs reduces the thermal loads on the cavity floor and entire tip by 82.4 % and 34.7 %, respectively, while the film cooling effects on the cavity floor and the entire tip are enhanced by 21.1 % and 72.2 %, respectively.

Numerical techniques for computing nonlinear dynamic characteristic of rotor-seal system

Xin Yan,Kun He,Jun Li,Zhenping Feng 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.5

A transient CFD procedure to compute the nonlinear dynamic characteristic of the coupled rotor-seal system was presented in thisstudy. In each time step, the displacement diffusion model was implemented to govern the mesh deformation, and the URANS (UnsteadyReynolds averaged Navier-Stokes) equations were solved to obtain the transient fluid force on the rotor surface for the free vibrations. With the obtained fluid force from the CFD solver, the nonlinear equations of motion for a simplified rotor-seal system were numericallysolved on the basis of external user defined routines. During each transient time step, the computed fluid force from the CFD solver andthe rotor motion from the user defined routines were transferred to each other timely. The rotor center trajectories, frequency spectrumand projection of Poincaré section were calculated to investigate the nonlinear dynamic performance of the single disk rotor-seal system. The effects of the rotational speed and pressure ratio on the vibration characteristic of the rotor-seal system were analyzed by the bifurcationtheorem. The results show that the coupled rotor-seal system experiences a period-one motion, resonance, periodic-doubling motion,quasi-periodic motion, and finally possible chaotic motion as the rotor speed increases. The pressure ratio has pronounced effect on thefrequency response of the first-order critical speed; however, it has little influence on the motion state as well as the frequency responseof the rotating speed. Although a constant-clearance annular smooth stator seal was selected as the research object in the current paper,the presented transient CFD method is still available for other complex annular seals, such as labyrinth seal, honeycomb seal, pocketdamper seal, etc.

Numerical investigations into the rubbing wear behavior of honeycomb seal

Xin Yan,Haibo Wang,Kun He 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

The rubbing wear behavior of the honeycomb land against labyrinth fin was investigated with finite-element-analysis method at a range of incursion conditions. The contact behaviors, material property, and material damage and failure are computed within the userdefined-subroutines. With the experimental data, the finite-element-analysis method was validated with respect to the frictional temperature and worn geometry. The effects of stator material, incursion depth, incursion rate and sliding velocity on the contact force, frictional temperature, material loss, and worn geometry are analyzed. The results show that the sliding velocity, final incursion depth and incursion rate are the important factors affecting the wear behaviors of honeycomb stator. The mushrooming extension is decreased with the increase of sliding velocity, and increased with the increase of incursion rate. At high sliding velocity and low incursion rate conditions, the material loss accounts more in the wear volume deformation compared to the plastic deformation.

Predictive and Prognostic Roles of Pathological Indicators for Patients with Breast Cancer on Neoadjuvant Chemotherapy

Xinyan Li,Mozhi Wang,Mengshen Wang,Xueting Yu,Jingyi Guo,Tie Sun,Litong Yao,Qiang Zhang,Yingying Xu 한국유방암학회 2019 Journal of breast cancer Vol.22 No.4

Currently, neoadjuvant chemotherapy is a standard therapeutic strategy for breast cancer, as it can provide timely and individualized chemo-sensitivity information and is beneficial for custom-designing subsequent treatment strategies. To accurately select candidates for neoadjuvant chemotherapy, the association between various immunohistochemical biomarkers of primary disease and tumor response to neoadjuvant chemotherapy has been investigated, and results have shown that certain pathological indicators evaluated after neoadjuvant chemotherapy are associated with long-term prognosis. The Food and Drug Administration (FDA) has recommended that complete pathological response can be used as a surrogate endpoint for neoadjuvant chemotherapy, which is related to better prognosis. Considering that residual tumor persists in the majority of patients after neoadjuvant chemotherapy, the value of various pathological indicators of residual disease in predicting the long-term outcomes is being extensively investigated. This review summarizes and compares various predictive and prognostic indicators for patients who have received neoadjuvant chemotherapy, and analyzes their efficacy in different breast cancer subtypes.

An Optimization Technique for Spatial Compound Joins Based on a Topological Relationship Query and Buffering Analysis in DSDBs with Partitioning Fragmentation

Xinyan Zhu,Chunhui Zhou,Wei Guo,Di Chen,Kezhong Liu 보안공학연구지원센터 2012 International Journal of Database Theory and Appli Vol.5 No.4

Updated Bayesian Network Meta-Analysis of Adjuvant Targeted Treatment Regimens for Early Human Epidermal Growth Factor Receptor-2 Positive Breast Cancer

Xinyan Li,Litong Yao,Mozhi Wang,Mengshen Wang,Xiang Li,Xueting Yu,Jingyi Guo,Haoran Dong,Xiangyu Sun,Yingying Xu 한국유방암학회 2020 Journal of breast cancer Vol.23 No.4

Purpose: Combining targeted agents with adjuvant chemotherapy prolongs survival in human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients, but also increases the risk of adverse effects. The updated results of 3 randomized controlled trials (RCTs) were reported in 2019. Given the lack of adequate head-to-head pairwise assessment for anti-HER2 agents, network meta-analysis facilitates obtaining more precise inference for evidence-based therapy. Methods: RCTs comparing at least 2 anti-HER2 regimens in an adjuvant setting for HER2- positive early-stage breast cancer (EBC) were included. Hazard ratios for overall survival (OS) and disease free survival (DFS), with respective 95% confidence intervals were pooled for assessment of efficacy. A Bayesian statistical model was used, and odds ratios (ORs) for adverse events (AEs) were used to pool effect sizes. Results: We demonstrated that 1-year trastuzumab plus chemotherapy had increased efficacy compared to shorter or longer treatment duration. The OR of cardiac events gradually increased from 6 months to 1 and 2-year trastuzumab arms, relative to chemotherapy only. Compared to trastuzumab plus chemotherapy, dual HER2-targeting therapies increased DFS, especially for hormone receptor negative patients. Dual anti-HER2 blockade regimens revealed an increased probability of gastrointestinal reactions. As a second agent, pertuzumab showed significantly higher DFS and OS. Conclusion: We conclude that 1-year adjuvant trastuzumab should remain as the standard treatment for HER2-positive EBC patients, as it has greater efficacy and a manageable proportion of AEs. Clinical efficacy can be increased for hormone receptor-negative tumors by including a second HER2-targeted agent to the treatment regimen. For hormone receptor-positive cases with basal disease, it is acceptable to reduce the risk of cardiotoxicity by shortening the duration of trastuzumab.

Preparation of titanium dioxide/tungsten disulfide composite photocatalysts with enhanced photocatalytic activity under visible light

Xinyan Xiao,Lili Zheng,Weiping Zhang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.1

Titanium dioxide/tungsten disulfide (TiO2/WS2) composite photocatalysts were fabricated via a one-step hydrothermal synthesis process, using TiCl4 as titanium source and bulk WS2 as sensitizer. The morphology, structure, specific surface area and optical absorption properties of the composite photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), specific surface area analyzer and ultraviolet-visible diffuse reflection spectrum (UV-vis DRS), respectively. The photocatalytic activity of as-prepared photocatalysts was evaluated by the degradation of methyl orange (MO) under illumination of 500W Xenon lamp. The results indicated that TiO2/WS2 composite photocatalysts possessed excellent photocatalytic activity, and ~95% of the degradation rate for MO was reached when molar ratio of WS2 to TiO2 was 0.004 and the irradiation time was 60 min. Moreover, the carrier trapping experiment and fluorescence spectra showed that •O2 − was the key component in the photocatalytic degradation process and O2 was reduced to be •O2 − by the electrons from the conduction band of TiO2 and WS2 for the degradation of MO.

Polymorphisms of Ionotropic Glutamate Receptor-Related Genes and the Risk of Autism Spectrum Disorder in a Chinese Population

Xinyan Xie,Fang Hou,Li Li,Yanlin Chen,Lingfei Liu,Xiu Luo1,Huaiting Gu,Xin Li,Jiajia Zhang,Jianhua Gong,Ranran Song 대한신경정신의학회 2019 PSYCHIATRY INVESTIGATION Vol.16 No.5

Objective: To evaluate the association of GRIK2 and NLGN1 with autism spectrum disorder in a Chinese population. Methods: We performed spatio-temporal expression analysis of GRIK2 and NLGN1 in the developing prefrontal cortex, and examined the expression of the genes in ASD cases and healthy controls using the GSE38322 data set. Following, we performed a case-control study in a Chinese population. Results: The analysis using the publicly available expression data showed that GRIK2 and NLGN1 may have a role in the development of human brain and contribute to the risk of ASD. Later genetic analysis in the Chinese population showed that the GRIK2 rs6922753 for the T allele, TC genotype and dominant model played a significant protective role in ASD susceptibility (respectively: OR=0.840, p=0.023; OR=0.802, p=0.038; OR=0.791, p=0.020). The NLGN1 rs9855544 for the G allele and GG genotype played a significant protective role in ASD susceptibility (respectively: OR=0.844, p=0.019; OR=0.717, p=0.022). After adjusting p values, the statistical significance was lost (p>0.05). Conclusion: Our results suggested that GRIK2 rs6922753 and NLGN1 rs9855544 might not confer susceptibility to ASD in the Chinese population.

Indole-3-acetic acid ameliorates dextran sulfate sodium-induced colitis via the ERK signaling pathway

Xinyan Qu,Yingying Song,Qingjun Li,Qi Xu,Yanru Li,Huimin Zhang,Xuemei Cheng,Charles R. Mackay,Quanbo Wang,Wei Liu 대한약학회 2024 Archives of Pharmacal Research Vol.47 No.3

Microbiota-derived catabolism of nutrients is closely related to ulcerative colitis (UC). The level of indole-3-acetic acid(IAA), a microbiota-dependent metabolite of tryptophan, was decreased signifi cantly in the feces of UC patients. Thus supplementationwith IAA could be a potential therapeutic method for ameliorating colitis. In this work, the protective eff ect ofsupplementation with IAA on dextran sulfate sodium (DSS)-induced colitis was evaluated, and the underlying mechanismwas elucidated. The results indicated that the administration of IAA signifi cantly relieved DSS-induced weight loss, reducedthe disease activity index (DAI), restored colon length, alleviated intestinal injury, and improved the intestinal tight junctionbarrier. Furthermore, IAA inhibited intestinal infl ammation by reducing the expression of proinfl ammatory cytokines andpromoting the production of IL-10 and TGF-β1. In addition, the ERK signaling pathway is an important mediator of variousphysiological processes including infl ammatory responses and is closely associated with the expression of IL-10. Notably,IAA treatment induced the activation of extracellular signal-regulated kinase (ERK), which is involved in the progressionof colitis, while the ERK inhibitor U0126 attenuated the benefi cial eff ects of IAA. In summary, IAA could attenuate theclinical symptoms of colitis, and the ERK signaling pathway was involved in the underlying mechanism. Supplementationwith IAA could be a potential option for preventing or ameliorating UC.