Preparation and characterization of activated carbons for SO_2 adsorption from Taixi anthracite by physical activation with steam

Yuwen Zhu,Jihui Gao,Fei Sun,Yukun Qin 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.12

Taixi anthracite was used as a precursor to prepare activated carbons (AC) for SO_2 adsorption from flue gas. In this work the activated carbons were prepared by physical activation with steam. Specifically, the effects of activation temperature and burn-off degree on the physico-chemical properties of the resulting AC samples were comparatively studied. The different types of pore volumes, pore size distributions and surface chemistries of the activated carbons on the SO_2 adsorption were also analyzed. The results show that the increasing burn-off leads to samples with continuous evolution of all types of pores except ultramicropore. The ultramicropore volume increases to a maximum of 0.169 cm^3/g at around 50% burn-off and then decreases for 850℃ activation. At higher activation temperature, the micropore volume decreases and the mesopore structure develops to a certain extent. For all the resulting AC samples,the quantities of the basic surface sites always appear much higher than the amount of the acidic sites. The activated carbon prepared with higher micropore volume, smaller median pore diameter and higher quantities of the basic surface sites represents better SO_2 sorption property.

Numerically Study of the Flow Field and Spatter Particles in Laser-based Powder Bed Fusion Manufacturing

Jiayue Wang,Yuwen Zhu,Hui Li,Sheng Liu,Shengnan Shen,Lei Wang,Shifeng Wen 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.4

Laser-based powder bed fusion (L-PBF) is an additive manufacturing (AM) technology that uses a high-energy–density laser to scan through a powder bed and completely melts the metal powder. The environment inside the printer chamber, including the flow field of the shielding gas and the spatter particles induced by laser–powder interactions, is essential for product quality. For the first time, this work built a full-size model of printer chamber, and numerically investigated the interaction between the shielding argon flow and the laser induced spatter particles with considering laser temperature. A full-size geometric model of a commercial L-PBF printer with a Gaussian heat source was constructed, as well as a movable particle-release source model for particle injection. The distribution of the argon flow field, the temperature field, and the trajectory and deposition of spatter particles, particularly above the workbench during the L-PBF process were quantitatively analyzed. The results show that the gas flow within 30 mm above the workbench is uniform, and in the upper region of the printer chamber, the flow field is disorderly. The laser can only induce high temperature and upward gas flow in a small region close to the workbench (the height less than 1.6 mm), and the laser induced velocity disturbance in rest regions of the L-PBF printer is negligible. Particles injected towards the outlet (ID4) are mostly blown into the outlet, and in the other four injection directions, more than 90% of spatter particles are deposited inside the printer chamber, especially more than 50% deposited on the workbench. Increasing the laser power (from 100 to 200 W) has little effect on particle deposition on the workbench. Results will be helpful for improving the L-PBF product quality.

Helmet CPAP versus Oxygen Therapy in Hypoxemic Acute Respiratory Failure: A Meta-Analysis of Randomized Controlled Trials

Xin Chen,Yuwen Luo,Yan Luo,Yun Li,Luqian Zhou,Zhe Zhu,Yitai Chen,Yuxia Huang 연세대학교의과대학 2016 Yonsei medical journal Vol.57 No.4

Purpose: The efficacy of helmet continuous positive airway pressure (CPAP) in hypoxemic acute respiratory failure (hARF) remainsunclear. The aim of this meta-analysis was to critically review studies that investigated the effect of helmet CPAP on gas exchange,mortality, and intubation rate in comparison with standard oxygen therapy. Materials and Methods: We performed a meta-analysis of randomized controlled trials (RCTs) by searching the PubMed, Embase,Cochrane library, OVID, and CBM databases, and the bibliographies of the retrieved articles. Studies that enrolled adults with hARF who were treated with helmet CPAP and measured at least one of the following parameters were included: gas exchange,intubation rate, in-hospital mortality rate. Results: Four studies with 377 subjects met the inclusion criteria and were analyzed. Compared to the standard oxygen therapy, helmet CPAP significantly increased the PaO2/FiO2 [weighted mean difference (WMD)=73.40, 95% confidence interval (95% CI): 43.92 to 102.87, p<0.00001], and decreased the arterial carbon dioxide levels (WMD=-1.92, 95% CI: -3.21 to -0.63, p=0.003), intubationrate [relative risk (RR)=0.21, 95% CI: 0.11 to 0.40, p<0.00001], and in-hospital mortality rate (RR=0.22, 95% CI: 0.09 to 0.50, p=0.0004). Conclusion: The results of this meta-analysis suggest that helmet CPAP improves oxygenation and reduces mortality and intubationrates in hARF. However, the significant clinical and statistical heterogeneity of the literature implies that large RCTs are neededto determine the role of helmet CPAP in different hypoxemic ARF populations.

Mechanism of SO_2 adsorption and desorption on commercial activated coke

Fei Sun,,Jihui Gao,Yuwen Zhu,,Yukun Qin 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.11

We used commercial activated coke (AC) as adsorbent and fixed-bed, FTIR, N_2 adsorption, ion chromatograph as research methods to study the SO2 removal mechanism in the presence of O_2 and H_2O and adsorbate (H_2SO_4)desorption mechanism by combined regeneration. The results showed that AC saturation sulfur retention (52.6 mg/g)in SO_2+O_2+H_2O atmosphere was 4.6 times as much as that (11.4mg/g) in SO_2+O_2 atmosphere and 5.0 times as much as that (10.6 mg/g) in SO_2+O_2 atmosphere at 90 ℃. O-2 and H_2O were necessary in AC desulfurization process. Reaction of SO_3 and H-2O (g) and condensation of sulfuric acid vapor were the dynamic of AC desulfurization process. Water vapor blowing in combined regeneration inhibited the reaction between H_2SO_4 and carbon, and consequently reduced the chemical lost of carbon. AC cumulative quality loss (53.6%) of five-times in C-R was still less than that (62.4%)of three-times in H-R. Water vapor blowing inhibited reactivation effect, as a result reducing the changes of AC pore structure and surface functional groups. Adsorbate H_2SO_4 generated in desulfurization evaporated to sulfuric acid vapor due to the high temperature in regeneration and was carried out by water vapor.

A LightGBM and XGBoost Learning Method for Postoperative Critical Illness Key Indicators Analysis

( Lei Han ),( Yiziting Zhu ),( Yuwen Chen ),( Guoqiong Huang ),( Bin Yi ) 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.8

Accurate prediction of critical illness is significant for ensuring the lives and health of patients. The selection of indicators affects the real-time capability and accuracy of the prediction for critical illness. However, the diversity and complexity of these indicators make it difficult to find potential connections between them and critical illnesses. For the first time, this study proposes an indicator analysis model to extract key indicators from the preoperative and intraoperative clinical indicators and laboratory results of critical illnesses. In this study, preoperative and intraoperative data of heart failure and respiratory failure are used to verify the model. The proposed model processes the datum and extracts key indicators through four parts. To test the effectiveness of the proposed model, the key indicators are used to predict the two critical illnesses. The classifiers used in the prediction are light gradient boosting machine (LightGBM) and eXtreme Gradient Boosting (XGBoost). The predictive performance using key indicators is better than that using all indicators. In the prediction of heart failure, LightGBM and XGBoost have sensitivities of 0.889 and 0.892, and specificities of 0.939 and 0.937, respectively. For respiratory failure, LightGBM and XGBoost have sensitivities of 0.709 and 0.689, and specificity of 0.936 and 0.940, respectively. The proposed model can effectively analyze the correlation between indicators and postoperative critical illness. The analytical results make it possible to find the key indicators for postoperative critical illnesses. This model is meaningful to assist doctors in extracting key indicators in time and improving the reliability and efficiency of prediction.

An MRTF-A–ZEB1–IRF9 axis contributes to fibroblast–myofibroblast transition and renal fibrosis

Zhao Qianwen,Shao Tinghui,Zhu Yuwen,Zong Gengjie,Zhang Junjie,Tang Shifan,Lin Yanshan,Ma Hongzhen,Jiang Zhifan,Xu Yong,Wu Xiaoyan,Zhang Tao 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-

Myofibroblasts, characterized by the expression of the matricellular protein periostin (Postn), mediate the profibrogenic response during tissue repair and remodeling. Previous studies have demonstrated that systemic deficiency in myocardin-related transcription factor A (MRTF-A) attenuates renal fibrosis in mice. In the present study, we investigated the myofibroblast-specific role of MRTF-A in renal fibrosis and the underlying mechanism. We report that myofibroblast-specific deletion of MRTF-A, achieved through crossbreeding Mrtfa-flox mice with Postn-CreERT2 mice, led to amelioration of renal fibrosis. RNA-seq identified zinc finger E-Box binding homeobox 1 (Zeb1) as a downstream target of MRTF-A in renal fibroblasts. MRTF-A interacts with TEA domain transcription factor 1 (TEAD1) to bind to the Zeb1 promoter and activate Zeb1 transcription. Zeb1 knockdown retarded the fibroblast–myofibroblast transition (FMyT) in vitro and dampened renal fibrosis in mice. Transcriptomic assays showed that Zeb1 might contribute to FMyT by repressing the transcription of interferon regulatory factor 9 (IRF9). IRF9 knockdown overcame the effect of Zeb1 depletion and promoted FMyT, whereas IRF9 overexpression antagonized TGF-β-induced FMyT. In conclusion, our data unveil a novel MRTF-A–Zeb1–IRF9 axis that can potentially contribute to fibroblast–myofibroblast transition and renal fibrosis. Screening for small-molecule compounds that target this axis may yield therapeutic options for the mollification of renal fibrosis.

Rapid flow measurement for high speed on/off valve based on coil current derivative

Qiang Gao,Yuchuan Zhu,Yuwen Wang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6

The average flow rate of a high speed on/off valve (HSV) is usually obtained by a flow sensor, which leads to pressure loss, structural complexity, and long test time. This paper proposes a rapid flow measurement for HSV based on the coil current derivative. The average flow rate is calculated by the effective opening time, which is solved by the critical moving time according to the proposed flow models. To estimate the critical moving time in real-time, an analytical model between the coil current derivative and the valve’s displacement is derived. Experiments indicate that the error between the linear and nonlinear flow model is small when the frequency is smaller than 50 Hz. Moreover, compared to the linear flow model, the average error of the nonlinear flow model decreases from 0.21 L/min to 0.12 L/min under 100 Hz. The proposed flow measurement method has advantages of rapid measurement, structural simplicity, non-contact, and easy to implement intelligence.

Analytical and Experimental Studies on All-Steel Buckling Restrained Brace with Double Steel Tubes

Jinhe Gao,Jiahuan Xi,Jiajun Ding,Yuwen Xu,Junwen Zhu,Yi Chang 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.1

This study proposes a new type of all-steel buckling restrained brace with double steel tubes composed of an inner round steel tube and an outer square steel tube, the inner core adopting a cruciform section and an H-section. These two types of cross-sectional inner cores have larger cross-sectional stiff ness than round bars and better meet the requirement that inner core should be easy to yield but not easy to buckle. In this study, a theoretical design method for designing the proposed BRB in a simplifi ed and optimal way is presented. The assembly scheme, constraint system, and overall structure are defi ned. The quasi-static tests of two brace specimens under a cyclic load are carried out to verify the brace's mechanical performance, axial strain distribution, and energy dissipation capacity. These results show that, relying on these two types of cross-sections, the hysteresis curves of all-steel buckling restrained braces with double-steel tubes are overall in good shape and stable. In addition, its energy dissipation performance is stable without any widespread instability phenomena. Also, the inner core has a stable plastic deformation capacity even after yielding, based on the comparative analysis of axial strain response of each components. Both specimens can meet the requirements of seismic design.

The Stability, and Efficacy Against Penicillin-Resistant Enterococcus faecium, of the Plectasin Peptide Efficiently Produced by Escherichia coli

( Xin Chen ),( Yaoan Wen ),( Ling Li ),( Jiawei Shi ),( Zhe Zhu ),( Yuwen Luo ),( Yun Li ),( Rui Chen ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.7

Plectasin, the first defensin extracted from a fungus (the saprophytic ascomycetePseudoplectania nigrella), is attractive as a prospective antimicrobial agent. The purpose of this study was to establish a bacterium-based production system and evaluate the antimicrobial activity of the resulting plectasin. A gene encoding plectasin, with the codon preference ofEscherichia coli, was optimized based on its amino acid sequence, synthesized using genesplicing with overlap extension PCR, and inserted into the expression vector pGEX-4T-1. The fusion protein was expressed in the soluble fraction of E. coli and purified using glutathione Stransferaseaffinity chromatography. Plectasin was cleaved from the fusion protein with thrombin and purified by ultrafiltration. The purified plectasin showed strong, concentrationdependent antimicrobial activity against gram-positive bacteria, including antibiotic-resistant bacteria, especially penicillin-resistant Enterococcus faecium. This antimicrobial activity wasequal to chemically synthesized plectasin and was maintained over a wide range of pH and temperatures. This soluble recombinant expression system in E. coli is effective for producing plectasin at a relatively lower cost, and higher purity and efficiency than prior systems, and might provide a foundation for developing a large-scale production system. Overall, plectasin shows potential as a novel, high-performance, and safe antibiotic for the treatment of refractory diseases caused by drug-resistant bacterial strains.