Structural first failure times under non-Gaussian stochastic behavior

( He Jun ),( Zai Chun Yan ) 서울시립대학교 산업기술연구소 2007 서울-상하이 포럼 Vol.2007 No.1

Loading capacity evaluation of composite box girder with corrugated webs and steel tube slab

He, Jun,Liu, Yuqing,Xu, Xiaoqing,Li, Laibin Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.4

This paper presents a type of composite box girder with corrugated webs and concrete filled steel tube slab to overcome cracking on the web and reduce self-weight. Utilizing corrugated steel web improves the efficiency of prestressing introduced into the top and bottom slabs due to the accordion effect. In order to understand the loading capacity of such new composite structure, experimental and numerical analyses were conducted. A full-scale model was loaded monotonically to investigate the deflection, strain distribution, loading capacity and stiffness during the whole process. The experimental results show that test specimen has enough loading capacity and ductility. Based on experimental works, a finite element (FE) model was established. The load-displacement curves and stress distribution predicted by FE model agree well with that obtained from experiments, which demonstrates the accuracy of proposed FE model. Moreover, simplified theoretical analysis was conducted depending on the assumptions which were confirmed by the experimental and numerical results. The simplified analysis results are identical with the tested and numerical results, which indicate that simplified analytical model can be used to predict the loading capacity of such composite girder accurately. All the findings of present study may provide reference for the application of such structure in bridge construction.

CHARACTERIZATIONS OF CENTRALIZERS AND DERIVATIONS ON SOME ALGEBRAS

He, Jun,Li, Jiankui,Qian, Wenhua Korean Mathematical Society 2017 대한수학회지 Vol.54 No.2

A linear mapping ${\phi}$ on an algebra $\mathcal{A}$ is called a centralizable mapping at $G{\in}{\mathcal{A}}$ if ${\phi}(AB)={\phi}(A)B= A{\phi}(B)$ for each A and B in $\mathcal{A}$ with AB = G, and ${\phi}$ is called a derivable mapping at $G{\in}{\mathcal{A}}$ if ${\phi}(AB)={\phi}(A)B+A{\phi}(B)$ for each A and B in $\mathcal{A}$ with AB = G. A point G in A is called a full-centralizable point (resp. full-derivable point) if every centralizable (resp. derivable) mapping at G is a centralizer (resp. derivation). We prove that every point in a von Neumann algebra or a triangular algebra is a full-centralizable point. We also prove that a point in a von Neumann algebra is a full-derivable point if and only if its central carrier is the unit.

Identification and Screening of Gene(s) Related to Susceptibility to Enterotoxigenic Escherichia coli F4ab/ac in Piglets

Li, Hejun,Li, Yuhua,Qiu, Xiaotian,Niu, Xiaoyan,Liu, Yang,Zhang, Qin Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.4

In 2004, Jorgensen and coworkers proposed the MUC4 gene as a candidate gene of enterotoxigenic Escherichia coli (ETEC) F4ab/ac receptor in piglets and a mutation of $G{\rightarrow}C$ in intron 7 of MUC4 was identified to be associated with the ETEC F4ab/ac adhesion phenotypes. In this study, we used 310 piglets of three breeds (Landrace, Large White and Chinese Songliao Black) to analyze the relationship between this mutation and the F4ab/ac adhesion phenotype. The results show that the genotypes at this site and the ETEC F4ab/ac adhesion phenotypes were not completely consistent, although they are very strongly associated. Among the individuals with genotype CC, which was identified as a resistant genotype to F4ab/ac adhesion, only 72.1% (124/172) were non-adhesive to ETEC F4ab and 77.9% (134/172) were non-adhesive to ETEC F4ac infections. This suggests that this mutation may not be the causative mutation for ETEC F4ab/ac adhesion, rather, the actual causative mutation may be in another gene closely linked to MUC4, or at aother site within the MUC4 gene. Our results also suggest that the receptors of F4ab and F4ac may be determined by two different but closely linked loci. In order to screen other genes related to F4ab/ac adhesion in piglets, the mRNA profiles from six full sib piglets, of which three were adhesive to ETEC F4ab/ac and three non-adhesive, were analyzed by suppression subtractive hybridization (SSH). One up-regulated gene, Ep-CAM, was selected for further analysis based on its role in the intestinal epithelial cells adhesion. Using real-time RT-PCR, we found that the Ep-CAM gene was significantly up-regulated in the piglets adhesive to F4ab/ac. It was mapped to SSC3q11-q14 by radiation hybrid mapping.

PREPARATION AND ELECTROCHEMICAL CAPACITIVE BEHAVIOR OF GRAPHENE BY MICROWAVE ASSISTED THERMAL REDUCTION OF GRAPHITE OXIDE IN HYDRAZINE HYDRATE

ZHEN SUN,Hejun Li,Kezhi Li,QIANGANG FU 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.6

Graphene platelets with a large scale have been synthesized by reduction of graphene oxide (GO)in aqueous solution of hydrazine hydrate under microwave irradiation (MWI). Microstructure ofthe graphene was characterized by X-ray di®raction (XRD), Raman spectroscopy, atomic forcemicroscopy (AFM) and transmission electron microscopy (TEM) together with the selected areaelectron di®raction (SAED). The electrochemical properties were evaluated by the analysis ofcyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1 M Na 2 SO 4aqueous solution. The results show that the as-prepared materials consist of crumpled, few-layer( ? 3 nm) thick and electronically conductive graphitic sheets. The supercapacitors fabricatedusing this material possess a low equivalent series resistance (ESR) value ? 1.6 ? and a highspeci¯c capacitance of 285 F ? g ? 1 . In addition, the graphene reduced under a diverse duration ofMWI displays a di®erent interlayer spacing, extent of reduction, level of graphitization andspeci¯c capacitances. The duration of MWI and the treatment methods strongly a®ect the mi-crostructure of graphene, and then dominate its electrochemical properties.

Identification of HDAC9 as a viable therapeutic target for the treatment of gastric cancer

Kai Xiong,Hejun Zhang,Yang Du,Jie Tian,Shigang Ding 생화학분자생물학회 2019 Experimental and molecular medicine Vol.51 No.-

Histone deacetylase inhibitors (HDACis) are a new class of anticancer drugs confirmed to have good therapeutic effects against gastric cancer (GC) in preclinical experiments, but most HDACis are non-selective (pan-HDACis), with highly toxic side effects. Therefore, it is necessary to screen HDAC family members that play key roles in GC as therapeutic targets to reduce toxic side effects. In this study, we evaluated the targeting specificity of the HDACi suberoylanilide hydroxamic acid (SAHA) for GC via fluorescence molecular imaging (FMI). In vitro FMI results showed that SAHA had higher binding affinity for GC cells than for normal gastric cells. In vivo FMI of gastric tumor-bearing mice confirmed that SAHA can be enriched in GC tissues. However, there was also a high-concentration distribution in normal organs such as the stomach and lungs, suggesting potential side effects. In addition, we found that among the HDAC family members, HDAC9 was the most significantly upregulated in GC cells, and we verified this upregulation in GC tissues. Further experiments confirmed that knockdown of HDAC9 inhibits cell growth, reduces colony formation, and induces apoptosis and cell cycle arrest. These results suggest that HDAC9 has an oncogenic role in GC. Moreover, HDAC9 siRNA suppressed GC tumor growth and enhanced the antitumor efficacy of cisplatin in GC treatment by inhibiting the proliferation and inducing the apoptosis of GC cells in vitro and in vivo. Our findings suggest that the development of HDAC9-selective HDACis is a potential approach to improve the efficacy of chemotherapy and reduce systemic toxicity.

One-Step Solvothermal Synthesis of Tetranitro-Cobalt Phthalocyanine/Reduced Graphene Oxide Composite

Lijuan Zhang,Hejun Li,QIANGANG FU,Zhanwei Xu,Kezhi Li,Jianfeng Wei 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.3

Tetranitro-cobalt phthalocyanine/reduced graphene oxide (TNCoPc/RGO) composite was prepared using ethylene glycol as reducing agent and precursor. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the composite. The electrochemical performance of the composite was examined by cyclic voltammetry and rotating disk electrode. The SEM observation and UV-Vis absorption spectrophotometer reveal that TNCoPc nanoparticles are closely contacted with RGO. The results show that the composite has a larger peak current and a higher current density than TNCoPc for oxygen reduction in an alkaline medium. This work offers a simple and environmental route for the synthesis of metal phthalocyanine (MPc)/RGO, which is adaptable to a wide range of applications in fuel cells.

Molybdenum Trioxide Dihydrate-Graphene Composite for Electrochemical Detection of Thiourea Molecule

Xinmeng Zhang,Kezhi Li,Hejun Li,Jinhua Lu,Leilei Zhang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.3

A novel electrochemical sensing platform was constructed based on a facile self-assembly procedure synthetic laminar molybdenum trioxide dihydrate (MoO3 · 2H2O)-graphene composite. Field emission scanning electron microscopy (FESEM), X-ray spectroscopy, X-ray diffraction (XRD) and Raman spectroscopy were employed to characterize the morphology and composition of the MoO3 · 2H2O-graphene composite. As a model molecule, thiourea was utilized to investigate the electrochemical behaviors of the MoO3 · 2H2O-graphene composite modified glass carbon electrode. The results show that the composite modified electrode has higher electron transfer rate than that of graphene modified electrode and bare glass carbon electrode meanwhile the peak currents of it has a good linear relationship with thiourea concentrations in the range of 2.40 X 10-3 − 19.3 X 10-3 M (R = 0.998) with detection limit of 4.99 µM (S/N = 3). This novel electrochemical sensor exhibits a higher absorption capacity (3.87 X 10-8 mol/cm2 ), a good reproducibility (1.41% relative standard deviation (RSD)), excellent anti-interference and a high stability. These excellent electrochemical properties of the MoO3 · 2H2O-graphene composite are attributed to the loose and porous structure and the synergistic effects between graphene and MoO3 · 2H2O, which make this composite material hold great potential applications for electrochemical sensor.

Reliability Evaluation of Power System Operations Considering Time-Varying Features of Components

Bo Hu,Ying Zheng,Hejun Yang,Yun Xia 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

The reliability of power system components can be affected by a numbers of factors such as the health level of components, external environment and operation environment of power systems. These factors also affect the electrical parameters of power system components for example the thermal capacity of a transmission element. The relationship of component reliability and power system is, therefore, a complex nonlinear function related to the above-mentioned factors. Traditional approaches for reliability assessment of power systems do not take the influence of these factors into account. The assessment results could not, therefore, reflect the short-term trend of the system reliability performance considering the influence of the key factors and provide the system dispatchers with enough information to make decent operational decisions. This paper discusses some of these important operational issues from the perspective of power system reliability. The discussions include operational reliability of power systems, reliability influence models for main performance parameters of components, time-varying reliability models of components, and a reliability assessment algorithm for power system operations considering the time-varying characteristic of various parameters. The significance of these discussions and applications of the proposed techniques are illustrated by case study results using the IEEE-RTS.

Reliability Evaluation of Power System Operations Considering Time-Varying Features of Components

Hu, Bo,Zheng, Ying,Yang, Hejun,Xia, Yun The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

The reliability of power system components can be affected by a numbers of factors such as the health level of components, external environment and operation environment of power systems. These factors also affect the electrical parameters of power system components for example the thermal capacity of a transmission element. The relationship of component reliability and power system is, therefore, a complex nonlinear function related to the above-mentioned factors. Traditional approaches for reliability assessment of power systems do not take the influence of these factors into account. The assessment results could not, therefore, reflect the short-term trend of the system reliability performance considering the influence of the key factors and provide the system dispatchers with enough information to make decent operational decisions. This paper discusses some of these important operational issues from the perspective of power system reliability. The discussions include operational reliability of power systems, reliability influence models for main performance parameters of components, time-varying reliability models of components, and a reliability assessment algorithm for power system operations considering the time-varying characteristic of various parameters. The significance of these discussions and applications of the proposed techniques are illustrated by case study results using the IEEE-RTS.