Preparation and Characterization of Poly(lactic acid) Micro- and Nanofibers Fabricated by Centrifugal Spinning

Lei Xia,Lin-lin Lu,Yu-Xia Liang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.7

In this paper, poly(lactic acid) (PLA) micro- and nanofibers were successfully prepared by centrifugal spinningwhich is a more simple and effective approach to produce micro/nanofibers. The morphology of fibers was investigated usingscanning electron microscopy (SEM), X-ray diffraction (XRD), while their thermal properties by differential scanningcalorimeter (DSC) and thermal gravimetric analysis (TGA). The results showed that the diameter of PLA fibers increasedsignificantly with increasing solution concentration and decreased slightly with increasing collection distance. It can becontrolled below 500 nm at the optimal process parameters which were found to be spinning solution concentration of 6 %,spinneret diameter of 0.11 mm, rotational speed of 5500 rpm and collecting distance of 15 cm. Although the crystallinity ofthe PLA fibers was weaker than that of the PLA pellets due to the insufficient adjustment of the molecular chain in rapidsolvent evaporation and short stretching time, it can be improved by increasing the rotational speed from 4500 to 7000 rpm. The glass transition temperature (Tg) and melting temperature (Tm) of the fibers were nearly keeping constant compared tothe PLA pellets. Its good degradability was demonstrated by the loss of fibers structure completely within 5 hours ofimmersion in NaOH at pH 13.

Clinical Risk Factor Analysis for Breast Cancer: 568,000 Subjects Undergoing Breast Cancer Screening in Beijing, 2009

Pan, Lei,Han, Li-Li,Tao, Li-Xin,Zhou, Tao,Li, Xia,Gao, Qi,Wu, Li-Juan,Luo, Yan-Xia,Ding, Hui,Guo, Xiu-Hua Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.9

Objectives: Although there are many reports about the risk of breast cancer, few have reported clinical factors including history of breast-related or other diseases that affect the prevalence of breast cancer. This study explores these risk factors for breast cancer cases reported in Beijing in 2009. Materials and Methods: Data were derived from a Beijing breast cancer screening performed in 2009, of 568,000 women, from 16 districts of Beijing, all aged between 40 and 60 years. In this study, multilevel statistical modeling was used to identify clinical factors that affect the prevalence of breast cancer and to provide more reliable evidence for clinical diagnostics by using screening data. Results and Conclusion: Those women who had organ transplants, compared with those with none, were associated with breast cancer with an odds ratio (OR)=65.352 [95% confidence interval (CI): 8.488-503.165] and those with solid breast mass compared with none had OR=1.384 (95% CI: 1.022-1.873). Malignant tendency was strongly associated with increased risk of breast cancer, OR=207.999(95% CI: 151.950-284.721). The risk of breast cancer increased with age, $OR_1$=2.759 (95% CI: 1.837-4.144, 56-60 vs. 40-45), $OR_2$=2.047 (95% CI: 1.394-3.077, 51-55 vs. 40-45), $OR_3$=1.668 (95% CI: 1.145-2.431). Normal results of B ultrasonic examination show a lower risk among participants, OR= 0.136 (95% CI: 0.085-0.218). Those women with ductal papilloma compared with none were associated with breast cancer, OR=6.524 (95% CI: 1.871-22.746). Therefore, this study suggests that clinical doctors should pay attention to these high-risk factors.

Iterative Generation Method of Arc Length Parameterized Curve Tool Path for Surface Machining from Short-Line Tool Path

Lei Lu,Jiang Han,Lian Xia,Cheng Fan,Haijun Liu,Shan Chen 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.10

To improve the application of the parametric curve tool path in surface machining, a method for generating arc-length parameterized toolpaths based on short-line toolpaths is proposed. The method first uses commercial CAM software to plan the short-line tool path. Then, the machining tool path with smooth continuous features is extracted. The smooth and continuous features are determined according to the chord length of the short-line tool path, and the extraction method is based on Chebyshev’s inequality of large numbers. After obtaining the smooth short-line trajectory, the iterative arc-length parameterized curve toolpath generation method is used to fit the discrete short-line toolpath. In the iterative process, the B-spline toolpath with parameterized chord length is obtained first. It is discretized according to the arc length difference information of the chord length B-spline. Finally, by continuously checking and inserting B-spline nodes, and fitting according to discrete points, the arc-length parameterized B-spline tool path is obtained. The feasibility of the method is verified with a part containing a sculpted surface, and two smooth arc-length parametric toolpaths are generated. In the end, the part is machined with the arc-length parameterized curve tool path.

Fabrication and Characterization of Copper-Exchanged BK7 Waveguides

Lei Huang,Xianfeng Chen,Yong Yang,Yuxing Xia 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.II

In this paper, we report fabrication of a copper-exchanged optical planar waveguide in BK7 glass by using ion exchange with ZnCl$_2$+Cu$_2$Cl$_2$ as ion source. The measured loss of the fabricated waveguides was as low as about 0.36 db/cm. The waveguides can hold 2 -- 4 modes with 5- to 30-minute exchange and 1 mode with 2- or 3-minute exchanges. The effective refractive index of each mode was determined by using the m-line test system at a wavelength of 0.65 $\mu$m. In addition, the cubic spline function interpolation method was employed to recover the gradient refractive index profiles of the copper-containing waveguides. The study on the annealing process for copper-exchanged waveguide is also discussed

A Novel Kinetic Analysis of Crystallization of Polypropylene (PP) in Dynamically-vulcanized PP/Ethylene-propylene-diene Rubber (EPDM) Blends Using an In-situ Measurement Technique

Lei Hu,Bin Yang,Yan-Li Deng,Fei-Xue Lu,Ru Xia,Zheng-Zhi Zheng,Ji-Bin Miao,Jia-Sheng Qian,Chuan-Ru Zhang,Peng Chen,Yu-Chuan Zhang 한국고분자학회 2017 폴리머 Vol.41 No.4

The effects of cooling medium temperatures and plastic/rubber ratios on solidification and crystallization kinetics of dynamically-vulcanized polypropylene/ethylene-propylene-diene rubber (PP/EPDM) blends were investigated with the aid of an in-situ measurement technique. The cooling medium temperature heavily influenced the solidification kinetics primarily due to a combination of latent heat liberated from the molten polymer and the heat transferred away via the metallic wall during the cooling period. Interestingly, the parameter C in three-parameter model was not only affected by the material properties, but also by the cooling condition, different from the previous literature. The crystallization kinetics analysis indicated that the effect of EPDM in the blends consisted of both nucleation-promoting effect (low EPDM loading) and steric effect (higher EPDM loading). The present kinetic analysis may be helpful to further studies on improving the product performances for industrial applications.

Robust Visual Inertial Odometry Estimation Based on Adaptive Interactive Multiple Model Algorithm

Lei Wang,Shicheng Xia,Hengliu Xi,Shuangxi Li,Le Wang 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.10

In this paper, we focus on the problem of motion tracking in unknown environments using visual and inertial sensors, commonly known as visual-Inertial odometer (VIO) tasks. Currently, there are two main types of estimation methods to achieve VIO estimation, the filter-based method and the optimization-based method. We combine multi-state-constraint Kalman filter (MSCKF) algorithm with interactive multi-model algorithm and propose a novel filter-based VIO method. Compared with the VIO algorithm based on extended Kalman filter (EKF), the MSCKF algorithm has less strict probability assumption and better accuracy and consistency. However, traditional EKF and MSCKF algorithms both adopt a single fixed system model, which is difficult to adapt to complex and changeable application scenarios. To solve this problem, we introduce the adaptive multi-model method into the MSCKF algorithm, and combine the two to build an interactive multi-model MSCKF (IMM-MSCKF) algorithm. In the proposed IMM-MSCKF algorithm, several model sub-filters are designed, and their results are fused by transition probability to obtain the optimal state estimation. The common data set KITTI is used to verify the proposed IMM-MSCKF algorithm. Experiment results show that the proposed novel algorithm has better estimation accuracy and robustness compared with other solutions based on multi-state constraint Kalman filter. The IMM-MSCKF algorithm can achieve long-term, high-precision and consistent real-time VIO tasks.

A novel pattern recognition protein of the Chinese oak silkmoth, Antheraea pernyi, is involved in the pro-PO activating system

Xia Lu Wan,Zhang Jing Hai,Ying Chen,You Lei Ma,Wen Jun Zou,Guo Yuan Ding,Wei Li,Ming Yi Zhao,Chun Fu Wu 생화학분자생물학회(구 한국생화학분자생물학회) 2013 BMB Reports Vol.46 No.7

Modular multilevel converter predictive control strategy based on energy balance

Xia, Xiangyang,Xu, Lei,Zhao, Xinxin,Zeng, Xiaoyong,Zhang, Jing,He, Yedan,Yi, Haigan The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.5

In MMC-HVDC (modular multilevel converter-based high-voltage direct current) applications, conventional control methods have defects such as complicated control and difficulty in controlling the internal energy of the converter. To ensure the safe and stable operation of an MMC-HVDC system, the problem of uneven internal energy distribution and increased fluctuations in the modular multilevel converter under asymmetrical network voltage conditions must be addressed. This paper has designed, a novel model predictive control (MPC) for MMC-HVDC applications. Through the proposed strategy, the switching states of all the MMC units can be optimized, which eliminates the circulating currents and achieves a voltage balance of the capacitor by redundant switching states. Moreover, an energy control circuit is established to adjust the DC bus power distribution in the MMC three-phase bridge arm. Thus, the symmetrical ac-side current can be realized, and the MMC internal energy imbalance caused by the transient process of the system can be avoided. Finally, the proposed novel predictive control strategy is tested via a case study. The obtained simulation and experimental results verify the effectiveness of the proposed control strategy.

Comparison of landslide susceptibility maps using random forest and multivariate adaptive regression spline models in combination with catchment map units

Lei Chu,Liang-Jie Wang,Jiang Jiang,Xia Liu,Kazuhide Sawada,Jinchi Zhang 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.2

Landslide susceptibility mapping (LSM) is a critical tool for mitigating the damages caused by geologic disasters. The selection of map units and mathematical models greatly affects the efficiency of LSM. To obtain the most appropriate combination of map units and mathematical models, four scales of catchment map units (CMUs) were analyzed and random forest (RF) and multivariate adaptive regression spline (MARSpline) models were applied in Gero City, Japan. The percentage of correctly identified landslides and the areas under the relative operating characteristic (ROC) curve were used to evaluate the model performances. The results indicate that the RF model had higher prediction accuracy than the MARSpline model, especially when the size of the CMU was 0.09 km2. A relatively high percentage of landslides fell into the high and very high landslide susceptibility classes (73%) and the lowest percentage of landslides fell into the very low landslide susceptibility classes (0.82%). The prediction-area (P-A) plots indicated that the prediction rates were higher for the RF model than the MARSpline model. The results of this study also suggest that the model accuracy can be increased if the appropriate CMU size is used. Therefore, the potential benefits of using the RF model in combination with the appropriate CMU size should be further explored using additional landslide-conditioning factors and other models.

Arginine Supplementation Recovered the IFN-γ-Mediated Decrease in Milk Protein and Fat Synthesis by Inhibiting the GCN2/eIF2α Pathway, Which Induces Autophagy in Primary Bovine Mammary Epithelial Cells

Xia, Xiaojing,Che, Yanyi,Gao, Yuanyuan,Zhao, Shuang,Ao, Changjin,Yang, Hongjian,Liu, Juxiong,Liu, Guowen,Han, Wenyu,Wang, Yuping,Lei, Liancheng Korean Society for Molecular and Cellular Biology 2016 Molecules and cells Vol.39 No.5

During the lactation cycle of the bovine mammary gland, autophagy is induced in bovine mammary epithelial cells (BMECs) as a cellular homeostasis and survival mechanism. Interferon gamma ($IFN-{\gamma}$) is an important antiproliferative and apoptogenic factor that has been shown to induce autophagy in multiple cell lines in vitro. However, it remains unclear whether $IFN-{\gamma}$ can induce autophagy and whether autophagy affects milk synthesis in BMECs. To understand whether $IFN-{\gamma}$ affects milk synthesis, we isolated and purified primary BMECs and investigated the effect of $IFN-{\gamma}$ on milk synthesis in primary BMECs in vitro. The results showed that $IFN-{\gamma}$ significantly inhibits milk synthesis and that autophagy was clearly induced in primary BMECs in vitro within 24 h. Interestingly, autophagy was observed following $IFN-{\gamma}$ treatment, and the inhibition of autophagy can improve milk protein and milk fat synthesis. Conversely, upregulation of autophagy decreased milk synthesis. Furthermore, mechanistic analysis confirmed that $IFN-{\gamma}$ mediated autophagy by depleting arginine and inhibiting the general control nonderepressible-2 kinase (GCN2)/eukaryotic initiation factor $2{\alpha}$ ($eIF2{\alpha}$) signaling pathway in BMECs. Then, it was found that arginine supplementation could attenuate $IFN-{\gamma}$-induced autophagy and recover milk synthesis to some extent. These findings may not only provide a novel measure for preventing the $IFN-{\gamma}$-induced decrease in milk quality but also a useful therapeutic approach for $IFN-{\gamma}$-associated breast diseases in other animals and humans.