Study of the Band-gap Structure of a 1D-photonic Crystal by Using Different Numerical Approaches

Liang-Yao Chen,Jian-Bo Chen,Yue-Rui Chen,Yan Shen,Wei-Xi Zhou,Jiu-Chun Ren,Yu-Xiang Zheng 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4

Comparative studies between the transfer matrices method (TMM) and plane wave method (PWM) approaches have been performed on 1D photonics crystal under different conditions to show the differences between these two kinds of calculations. TMM is suitable for the design of 1D photonic crystal device with high precision and is in good agreement with experimental results, but is not suitable for the 2D and 3D photonic structures which are limited by the complicated boundary conditions at micro interfaces. The result based on the PWM approach to deal approximately with the photonic structure in approximation has not yet been strictly verified by experiment, not even for 1D photonic crystal structures. More efforts will be required to explore its validation under all physical conditions to enhance its application.

Application of magnetic resonance imaging with intraoperative color Doppler ultrasound in the treatment of patients with polyacrylamide hydrogel injected for breast augmentation: a retrospective study of 204 cases for 12 years

Xi Bu,Jian-Xun Ma,You-Chen Xia,Bi Li,Yue Lang,Shi-Lu Yin 대한외과학회 2024 Annals of Surgical Treatment and Research(ASRT) Vol.106 No.1

Purpose: Polyacrylamide hydrogel (PAHG), which had been used widely for breast augmentation, has been banned for more than 15 years. Patients who had been injected PAHG for breast augmentation need evacuation surgery to remove as much as possible. To provide a series of diagnosis and treatment process MRI and intraoperative color Doppler ultrasound are combined for maximal removal of PAHG. Methods: The patients who received evacuation surgery in Peking University Third Hospital from 2010 to 2022 after PAHG injection for breast augmentation were included in this research. MR scanning was performed preoperatively and postoperatively in some of these patients and color Doppler ultrasound was applied to help evacuate PAHG intraoperatively. The mean clearance rate of PAHG was calculated according to the MRI outcomes. Results: Two hundred and 4 patients had received evacuation surgery after PAHG injection for breast augmentation with an average age of 42.8 years and an average body mass index of 21.2 kg/m2. The average PAHG retention time was 13.5 years. Among them, 52 patients underwent pre- and postoperative MRI scanning. The mean three-dimensional (3D) volume of PAHG was 684.8 mL (range, 350.0–1,123.9 mL), and the average residual 3D volume of PAHG was 53.7 mL (range, 12.4–98.3 mL). The mean clearance rate was 92.1%. Conclusion: MRI and intraoperative color Doppler ultrasound can provide effective and precise location information of PAHG for evacuation surgery, which is a reliable method to ensure the maximal removal of PAHG.

Depression and APOEε4 Status in Individuals with Subjective Cognitive Decline: A Meta-Analysis

Yue-ping Huang,Ju-jun Xue,Chao Li,Xi Chen,Hong-juan Fu,Teng Fei,Peng-xiang Bi 대한신경정신의학회 2020 PSYCHIATRY INVESTIGATION Vol.17 No.9

Objective To evaluate the associative role of depression and apolipoprotein E epsilon 4 allele (APOEε4) in subjective cognitive decline(SCD) and its progression to objective cognitive decline. Methods After literature search in electronic databases, studies were selected by following precise eligibility criteria. Meta-analyses were performed to examine the role of APOEε4 and depression in SCD or its progression to mild cognitive impairment (MCI) or dementia. Results APOEε4 positivity was not different between SCD and normal individuals but was significantly higher in individuals with SCD plus than in normal individuals [odds ratio: 2.39 (95% CI: 1.87, 3.05); p<0.00001] and in SCD converters than in non-converters [odds ratio: 5.19 (95% CI: 2.36, 11.42); p<0.00001]. Depression was significantly higher in individuals with SCD [standardized mean difference: 0.63 (0.45, 0.82); p<0.00001] and SCD plus [standardized mean difference: 0.83 (0.43, 1.22); p<0.0001] than in normal individuals. However, depression was not different between SCD and MCI or between SCD converters and non-converters. Age of SCD converters was higher than non-converters [mean difference: 2.95 years (0.58, 5.31)]. Conclusion Whereas APOEε4 positivity was higher in SCD plus and SCD converters, depression was higher in SCD and SCD plus but was not different between SCD and MCI.

A Novel Phase Locked Loop for Grid-Connected Converters under Non-Ideal Grid Conditions

Long-Yue Yang,Chong-Lin Wang,Jian-Hua Liu,Chen-Xi Jia 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.1

Grid synchronization is one of the key techniques for the grid-connected power converters used in distributed power generation systems. In order to achieve fast and accurate grid synchronization, a new phase locked loop (PLL) is proposed on the basis of the complex filter matrixes (CFM) orthogonal signal generator (OSG) crossing-decoupling method. By combining first-order complex filters with relation matrixes of positive and negative sequence voltage components, the OSG is designed to extract specific frequency orthogonal signals. Then, the OSG mathematical model is built in the frequency-domain and time-domain to analyze the spectral characteristics. Moreover, a crossing-decoupling method is suggested to decouple the fundamental voltage. From the eigenvalue analysis point of view, the stability and dynamic performance of the new PLL method is evaluated. Meanwhile, the digital implementation method is also provided. Finally, the effectiveness of the proposed method is verified by experiments under unbalanced and distorted grid voltage conditions.

A Novel Phase Locked Loop for Grid-Connected Converters under Non-Ideal Grid Conditions

Yang, Long-Yue,Wang, Chong-Lin,Liu, Jian-Hua,Jia, Chen-Xi The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.1

Grid synchronization is one of the key techniques for the grid-connected power converters used in distributed power generation systems. In order to achieve fast and accurate grid synchronization, a new phase locked loop (PLL) is proposed on the basis of the complex filter matrixes (CFM) orthogonal signal generator (OSG) crossing-decoupling method. By combining first-order complex filters with relation matrixes of positive and negative sequence voltage components, the OSG is designed to extract specific frequency orthogonal signals. Then, the OSG mathematical model is built in the frequency-domain and time-domain to analyze the spectral characteristics. Moreover, a crossing-decoupling method is suggested to decouple the fundamental voltage. From the eigenvalue analysis point of view, the stability and dynamic performance of the new PLL method is evaluated. Meanwhile, the digital implementation method is also provided. Finally, the effectiveness of the proposed method is verified by experiments under unbalanced and distorted grid voltage conditions.

Research on the Efficiency and Influencing Factors of Korea's Foreign Direct Investment in RCEP Partners

Wang Xin-Yue,Xi Chen,Li Chen,Qing Wang 한국무역학회 2022 Journal of Korea trade Vol.26 No.4

Purpose – In this paper, we, taking South Korea's foreign direct investment in RCEP partners as an example, will examine its investment efficiency in these countries and analyze the main influencing factors, making suggestions for further liberalizing and facilitating its investment in and even for promoting its trade and economic cooperation with them. Design/methodology – In this study, we look at the panel data of South Korea and the other 13 RCEP countries (Brunei excluded) from 2000 to 2019 and apply the stochastic frontier analysis to measure its foreign direct investment efficiency and explore the influencing factors in RCEP countries. We examine the investment potential of South Korea in these places. Findings – We find that South Korea's average investment efficiency in RCEP countries reached 0.62, indicating large investment potential. We also find that its investment efficiency in RCEP partners was heterogeneous. Our study reveals that South Korea’s foreign direct investment is significantly positively correlated with the market size and population of the two countries, as well as with whether the host country has a coastline and rich natural resources, while negatively with geographic distance. It shows that free trade agreements, economic freedom, and regulatory quality play significant roles in improving investment efficiency. Originality/value – Through theoretical and empirical analysis, we deal with the efficiency and influencing factors of South Korea's direct investment in RCEP partners, proposing new drivers for facilitating its trade and investment in these countries and comprehensively evaluating the efficiency and revealing the trend of its FDI in these countries. In this paper, we put forward a solid theoretical basis for empirical analysis of the future economic and trade development between South Korea and its RCEP partners and give objective insights for further improving its foreign direct investment efficiency and tapping its investment potential.

Characterization of strain rate sensitivity and activation volume using the indentation relaxation test

Xu, Baoxing,Yue, Zhufeng,Chen, Xi Institute of Physics [etc.] 2010 Journal of Physics. D, Applied Physics Vol.43 No.24

<P>We present the possibility of extracting the strain rate sensitivity, activation volume and Helmholtz free energy (for dislocation activation) using just one indentation stress relaxation test, and the approach is demonstrated with polycrystalline copper. The Helmholtz free energy measured from indentation relaxation agrees well with that from the conventional compression relaxation test, which validates the proposed approach. From the indentation relaxation test, the measured indentation strain rate sensitivity exponent is found to be slightly larger, and the indentation activation volume much smaller, than their counterparts from the compression test. The results indicate the involvement of multiple dislocation mechanisms in the indentation test.</P>

Feasibility of Free-Breathing, Non-ECG-Gated, Black-Blood Cine Magnetic Resonance Images With Multitasking in Measuring Left Ventricular Function Indices

Peng Pengfei,Yue Xun,Tang Lu,Wu Xi,Deng Qiao,Wu Tao,Cai Lei,Liu Qi,Xu Jian,Huang Xiaoqi,Chen Yucheng,Diao Kaiyue,Sun Jiayu 대한영상의학회 2023 Korean Journal of Radiology Vol.24 No.12

Objective: To clinically validate the feasibility and accuracy of cine images acquired through the multitasking method, with no electrocardiogram gating and free-breathing, in measuring left ventricular (LV) function indices by comparing them with those acquired through the balanced steady-state free precession (bSSFP) method, with multiple breath-holds and electrocardiogram gating. Materials and Methods: Forty-three healthy volunteers (female:male, 30:13; mean age, 23.1 ± 2.3 years) and 36 patients requiring an assessment of LV function for various clinical indications (female:male, 22:14; 57.8 ± 11.3 years) were enrolled in this prospective study. Each participant underwent cardiac magnetic resonance imaging (MRI) using the multiple breath-hold bSSFP method and free-breathing multitasking method. LV function parameters were measured for both MRI methods. Image quality was assessed through subjective image quality scores (1 to 5) and calculation of the contrast-to-noise ratio (CNR) between the myocardium and blood pool. Differences between the two MRI methods were analyzed using the Bland–Altman plot, paired t-test, or Wilcoxon signed-rank test, as appropriate. Results: LV ejection fraction (LVEF) was not significantly different between the two MRI methods (P = 0.222 in healthy volunteers and P = 0.343 in patients). LV end-diastolic mass was slightly overestimated with multitasking in both healthy volunteers (multitasking vs. bSSFP, 60.5 ± 10.7 g vs. 58.0 ± 10.4 g, respectively; P < 0.001) and patients (69.4 ± 18.1 g vs. 66.8 ± 18.0 g, respectively; P = 0.003). Acceptable and comparable image quality was achieved for both MRI methods (multitasking vs. bSSFP, 4.5 ± 0.7 vs. 4.6 ± 0.6, respectively; P = 0.203). The CNR between the myocardium and blood pool showed no significant differences between the two MRI methods (18.89 ± 6.65 vs. 18.19 ± 5.83, respectively; P = 0.480). Conclusion: Multitasking-derived cine images obtained without electrocardiogram gating and breath-holding achieved similar image quality and accurate quantification of LVEF in healthy volunteers and patients.

Study on Joint Simulation of Very Fast Transient Overvoltage and Transient Enclosure Voltage in 1000 kV GIS

Zhang Yan-Ze,Chen Xiao-Yue,Si Jun-Jie,He Ze-Yu,Wen Xi-Shan 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.5

Disconnector operation in GIS generates VFTO and TEV, which threaten device insulation and personnel safety. In order to calculate VFTO and TEV more accurately, this paper proposes a VFTO-TEV joint simulation model. Among them, dynamic arc model is used to reflect the dynamic characteristics of high frequency AC arc. In order to reflect the electromagnetic leakage phenomenon caused by the impedance mismatch of high-frequency electromagnetic waves, and the influence of the transient potential difference formed by the transient electromagnetic field on grounding grid on TEV, the geometric structures of high-voltage bushing, grounding pillars and grounding grid are modeled to obtain their respective frequency-dependent admittance matrices, which are converted into corresponding broadband equivalent circuit models by combining vector fitting method and impedance synthesis method. The above modeling method is applied to the 1000 kV GIS test circuit, and the simulation model is built in the ATP-EMTP electromagnetic transient program, and the joint simulation research of VFTO and TEV is carried out. The results show that at each measurement point of the test circuit, the amplitude error of the VFTO obtained by simulation and actual measurement is mostly less than 7%, and the frequency spectrum both contains the main frequency components of 18 MHz and 25 MHz; Compared with the traditional calculation model of obtaining VFTO/TEV using CIGRE model/Petersen's law, the amplitude of VFTO and TEV obtained by joint simulation model is lower and contains richer high-frequency components. In addition, the opening speed of 0.8 m/s also corresponds to the maximum point of the VFTO amplitude of the test circuit. Finally, based on the above modeling method, the effectiveness of adding ferrite beads to suppress VFTO is verified by simulation. © 2017 Elsevier Inc. All rights reserved.

Optimal Tracking Control for Discrete-time Systems with Multiple Input Delays under Sinusoidal Disturbances

Shi-Yuan Han,Yue-Hui Chen,Dong Wang,Gong-You Tang,Xi-Xin Yang 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.2

This study researches the tracking control problem for discrete-time systems with multiple input delays affected by sinusoidal disturbances. This study is organized around the expression of sinusoidal and disturbances and the delay-free transformation. First, based on the periodic characteristic of the sinusoidal disturbance, the sinusoidal disturbances are considered as the output of an exosystem. By proposing a discrete variable transformation, the discrete-time system with multiple input delays and the quadratic performance index are transformed into equivalent delay-free ones. Then, by constructing an augmented system that comprises the states of the exosystems of sinusoidal disturbances, the reference input, and the delay-free transformation systems, the original tracking problem is transformed into the optimal tracking problem for a delay-free system with respect to the simplified performance index. The optimal tracking control (OTC) law is obtained from Riccati and Stein equations. The existent and uniqueness of the optimal control law is proved. A reduced-order observer is constructed to solve the problem of physically realizable for the items of the reference input and sinusoidal disturbances. Finally, the feasibility and effectiveness of the proposed approaches are validated by numerical examples.