Structure and Properties of Aromatic Polyimide Fibers Fabricated by a Novel “Reaction-Spinning” Method

Zhentao Li,Jie Dong,Jian Huang,Tao Guo,Shihua Wang,Xin Zhao,Qinghua Zhang 한국고분자학회 2020 Macromolecular Research Vol.28 No.1

In this work, two sets of high performance polyimide (PI) fibers fabricated by a more environmentally-friendly and highly efficient “reaction-spinning” method were firstly reported. The relationship between the spinning rate, chemical structure and the imidization degree of the PI precursor fibers were investigated, and the results indicated a moderate low spinning speed and relatively flexible molecular chains are both favorable for the partial imidization reaction in the spinning process. 2D WAXD results demonstrate that the rigid PDA-based PI fibers possess a higher alignment of polymer chains along the fiber axis during the spinning compared to the flexible ODA-based PIs, resulting in enhanced mechanical properties, with the tensile strength of 1.2-2.8 GPa and modulus of 53.6-111.2 GPa, respectively. Meanwhile, ODA sets of PI fibers exhibit a higher loop strength and knot strength than the commercial Aramid and PBO fibers. The process used in this study has a significant potential for realizing industrial level production of high strength and high modulus PI fibers.

LRIG1 Enhances Chemosensitivity by Modulating BCL-2 Expression and Receptor Tyrosine Kinase Signaling in Glioma Cells

Zhentao Guo,Qianxue Chen,Baohui Liu,Daofeng Tian,Shenqi Zhang,Mingchang Li 연세대학교의과대학 2014 Yonsei medical journal Vol.55 No.5

Purpose: Leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) are an inhibitor of receptor tyrosine kinases (RTKs) that was discovered in recent years, and many studies showed that LRIG1 is a tumor suppressor gene and may be related to tumor drug resistance. In this study, we explored whether LRIG1 protein expression can improve the chemosensitivity of glioma cells and what was its mechanism. Materials and Methods: We collected 93 cases of glioma tissues and detected the expression of LRIG1 and BCL-2. We constructed a multidrugresistance cell line U251/multidrug resistance (MDR) and examined the change of LRIG1 and BCL-2 at mRNA and protein expression levels. LRIG1 expressionwas upregulated in U251/MDR cells and we detected the change of multidrug resistance. Meanwhile, we changed the expression of LRIG1 and BCL-2 and explored the relationship between LRIG1 and BCL-2. Finally, we also explored the relationship between LRIG1 and RTKs. Results: LRIG1 was negatively correlated with BCL-2 expression in glioma tissue and U251/MDR cells, and upregulation of LRIG1 can enhance chemosensitivity and inhibit BCL-2 expression. Furthermore, LRIG1 was negatively correlated with RTKs in U251/MDR cells. Conclusion: These results demonstrated that LRIG1 can improvechemosensitivity by modulating BCL-2 expression and RTK signaling in glioma cells.

Hydroxychloroquine and chloroquine: a potential and controversial treatment for COVID-19

Li Zou,Lijun Dai,Xingyu Zhang,Zhaohui Zhang,Zhentao Zhang 대한약학회 2020 Archives of Pharmacal Research Vol.43 No.8

A novel coronavirus, later named SARS-CoV-2,was fi rst reported in China in December 2019 and subsequentlywidely identifi ed in the United States, Japan, SouthKorea, France, India, and other countries. The diseasecaused by SARS-CoV-2 infection was called COVID-19. The high fatality and morbidity rates of COVID-19 makeit the third largest global epidemic in this century. However,there are currently no approved antiviral drugs for theCOVID-19 treatment. Recently, two old antimalarial drugs,hydroxychloroquine and chloroquine, have been found toexert anti-SARS-CoV-2 eff ects both in vitro and in vivo. Preliminaryclinical evidence suggests these drugs may havean eff ect on the treatment of COVID-19. Herein, we reviewthe pharmacokinetics characteristics and antiviral eff ects ofthese drugs, in addition to their side eff ects and clinical evidenceof their use for the COVID-19 treatment.

Influence of Relative Humidity on the Temperature Increase of a Power Converter

Yang Xu,Hao Chen,Zhentao Hu,Dong Li 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.3

As a vital part of renewable energy and electrical traction, power converters are supposed to have high reliability and good performance. However, power semiconductors produce considerable heat when the power converter works, which results in high junction temperatures that lower the reliability and performance of the power semiconductors. Many studies show that ambient humidity has a significant effect on power devices, but the influence of high humidity on junction temperatures has yet to be studied. Therefore, this paper presents a thermal model for power converters in moist air to obtain the junction temperature increase, which is utilized for the power converter used in a Switched Reluctance Motor System. Simulation results show that the law of converter temperature distribution is independent of the relative humidity in the case of fixed ambient temperature, whereas the temperature in the power converter decreases as the ambient relative humidity increases. These simulation results are validated with the experimental results.

Influence of Relative Humidity on the Temperature Increase of a Power Converter

Xu, Yang,Chen, Hao,Hu, Zhentao,Li, Dong The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.3

As a vital part of renewable energy and electrical traction, power converters are supposed to have high reliability and good performance. However, power semiconductors produce considerable heat when the power converter works, which results in high junction temperatures that lower the reliability and performance of the power semiconductors. Many studies show that ambient humidity has a significant effect on power devices, but the influence of high humidity on junction temperatures has yet to be studied. Therefore, this paper presents a thermal model for power converters in moist air to obtain the junction temperature increase, which is utilized for the power converter used in a Switched Reluctance Motor System. Simulation results show that the law of converter temperature distribution is independent of the relative humidity in the case of fixed ambient temperature, whereas the temperature in the power converter decreases as the ambient relative humidity increases. These simulation results are validated with the experimental results.

Virtual Network Embedding based on Node Connectivity Awareness and Path Integration Evaluation

( Zhiyuan Zhao ),( Xiangru Meng ),( Yuze Su ),( Zhentao Li ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.7

As a main challenge in network virtualization, virtual network embedding problem is increasingly important and heuristic algorithms are of great interest. Aiming at the problems of poor correlation in node embedding and link embedding, long distance between adjacent virtual nodes and imbalance resource consumption of network components during embedding, we herein propose a two-stage virtual network embedding algorithm NA-PVNM. In node embedding stage, resource requirement and breadth first search algorithm are introduced to sort virtual nodes, and a node fitness function is developed to find the best substrate node. In link embedding stage, a path fitness function is developed to find the best path in which available bandwidth, CPU and path length are considered. Simulation results showed that the proposed algorithm could shorten link embedding distance, increase the acceptance ratio and revenue to cost ratio compared to previously reported algorithms. We also analyzed the impact of position constraint and substrate network attribute on algorithm performance, as well as the utilization of the substrate network resources during embedding via simulation. The results showed that, under the constraint of substrate resource distribution and virtual network requests, the critical factor of improving success ratio is to reduce resource consumption during embedding.

Cognitive Virtual Network Embedding Algorithm Based on Weighted Relative Entropy

( Yuze Su ),( Xiangru Meng ),( Zhiyuan Zhao ),( Zhentao Li ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.4

Current Internet is designed by lots of service providers with different objects and policies which make the direct deployment of radically new architecture and protocols on Internet nearly impossible without reaching a consensus among almost all of them. Network virtualization is proposed to fend off this ossification of Internet architecture and add diversity to the future Internet. As an important part of network virtualization, virtual network embedding (VNE) problem has received more and more attention. In order to solve the problems of large embedding cost, low acceptance ratio (AR) and environmental adaptability in VNE algorithms, cognitive method is introduced to improve the adaptability to the changing environment and a cognitive virtual network embedding algorithmbased on weighted relative entropy (WRE-CVNE) is proposed in this paper. At first, the weighted relative entropy (WRE) method is proposed to select the suitable substrate nodes and paths in VNE. In WRE method, the ranking indicators and their weighting coefficients are selected to calculate the node importance and path importance. It is the basic of the WRE-CVNE. In virtual node embedding stage, the WRE method and breadth first search (BFS) algorithm are both used, and the node proximity is introduced into substrate node ranking to achieve the joint topology awareness. Finally, in virtual link embedding stage, the CPU resource balance degree, bandwidth resource balance degree and path hop counts are taken into account. The path importance is calculated based on the WRE method and the suitable substrate path is selected to reduce the resource fragmentation. Simulation results show that the proposed algorithm can significantly improve AR and the long-term average revenue to cost ratio (LTAR/CR) by adjusting the weighting coefficients in VNE stage according to the network environment. We also analyze the impact of weighting coefficient on the performance of the WRE-CVNE. In addition, the adaptability of the WRE-CVNE is researched in three different scenarios and the effectiveness and efficiency of the WRE-CVNE are demonstrated.