Arm Balance Control Scheme of Novel Isolated Modular Multilevel Converter (I-MMC)

Lin. Lin,Qi. Chen,Xingang. Wu,Chuang. Liu,Jinming. Li,Dehao. Kong 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper introduces an isolated modular multilevel converter (I-MMC) structure which can transport the energy power from LVDC to HVDC and HVAC with single-stage, and the arm balance control strategy. The paper also analyzes the reason of leading to the unbalance in arm, establish the relevant model, and propose the unbalance control strategy of the arm. Finally, the method is verified by simulation and experiment.

High-Frequency Isolated Medium-Voltage AC Grid-connected PV Power Generation System Structure based on DC Bus Collection

Lin. Lin,Qi. Chen,Xingang. Wu,Chuang. Liu,Haoran. Zhang,Dongfeng. Yang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper proposes an isolated mediumvoltage AC grid-connected PV power generation system structure based on DC bus collection with high-frequency link concept. The proposed system structure consists of centralized photovoltaic power plant, inverter unit based on isolated bridge converter (I-BC), and capacitor at the junction of dc bus. PV plant is divided into many arrays, each PV array is connected in parallel with each phase inverter unit. Inverter unit is composed of two I-BC. Compare with conventional two-stage PV inverter, I-BC can totally eliminate the individual DC-link capacitors at the highvoltage side, which leads to extremely reduced system volume and voltage-balancing control between individual capacitors. Second harmonic power oscillations seen in typical system structure can also be eliminated or reduced through use of the proposed system. This paper presents the analysis and operation of the proposed PV system structure with experimental results on a scaled-down laboratory.

Curcumol Induces Apoptosis in SPC-A-1 Human Lung Adenocarcinoma Cells and Displays Anti-neoplastic Effects in Tumor Bearing Mice

Tang, Qi-Ling,Guo, Ji-Quan,Wang, Qi-You,Lin, Hai-Shu,Yang, Zhou-Ping,Peng, Tong,Pan, Xue-Diao,Liu, Bing,Wang, Su-Jun,Zang, Lin-Quan Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.6

Curcumol is a sesquiterpene originally isolated from curcuma rhizomes, a component of herbal remedies commonly used in oriental medicine. Its beneficial pharmacological activities have attract significant interest recently. In this study, anti-cancer activity of curcumol was examined with both in vitro and in vivo models. It was found that curcumol exhibited time- and concentration-dependent anti-proliferative effects in SPC-A-1 human lung adenocarcinoma cells with cell cycle arrest in the G0/G1 phase while apoptosis-induction was also confirmed with flow cytometry and morphological analyses. Interestingly, curcumol did not display growth inhibition in MRC-5 human embryonic lung fibroblasts, suggesting the anti-proliferative effects of curcumol were specific to cancer cells. Anti-neoplastic effects of curcumol were also confirmed in tumor bearing mice. Curcumol (60 mg/ kg daily) significantly reduced tumor size without causing notable toxicity. In conclusion, curcumol appears a favorable anti-cancer candidate for further development.

Metrological performance investigation of swirl flowmeter affected by vortex inflow

Qi Liu,Jia-hui Ye,Guang Zhang,Zhe Lin,Hong-guang Xu,Zu-chao Zhu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6

In fluid transportation industries, long straight transition pipelines upstream of flowmeters are required to eliminate the influence of disturbed inflow on flow metering accuracy. To ensure an accurate flow measurement, the straight transition pipeline, which is often lengthy, can be shortened, particularly when the installation space is limited. However, the characteristics of disturbed flow (mainly characterized by vortex inflow) evolving along the straight transition pipeline to affect the metrological performance must be investigated for optimizing the pipeline length. The objective of this study was to investigate the metrological performance of a swirl flowmeter affected by the vortex inflow caused by flow regulation with a sleeve valve. The effect of a straight transition pipeline length upstream of a swirl flowmeter on the evolving characteristics of the vortex inflow was investigated experimentally and by conducting a numerical simulation under flow regulation parameters, including valve openings and flow velocities. The flow coefficients for different straight transition pipeline lengths were investigated to verify the flow simulation. The periodic pressure variation in the swirl flowmeter was monitored and its corresponding characteristic frequency was analyzed. It was found that the metrological characteristics of the swirl flowmeter were extremely affected by a smaller valve opening, which can be improved by lengthening the straight transition pipeline. By analyzing the velocity vector and vorticity in the internal flow field, the vortex inflow was found to be vulnerable to dissipation within a longer straight transition pipeline. The average vorticity at the cross-section of the entrance to the swirl flowmeter was adopted to evaluate the inflow vortex intensity. Additionally, a power curve model was established to assess the critical characteristic frequency determined by the maximum unaffected inflow vorticity for different straight transition pipeline lengths. This study can provide helpful insights to the metrological performance and pipeline arrangement in the field of fluid transportation engineering.

Development of Integrated Multi-Station System to Precisely Detect and Mitigate Surface Damage on Fused Silica Optics

Lin-Jie Zhao,Jian Cheng,Ming-Jun Chen,Xiao-Dong Yuan,Wei Liao,Hao Yang,Qi Liu,Hai-Jun Wang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.1

In high power laser facility, irreversible damage on fused silica optics, induced by laser irradiation or processing, seriously affects the service life of optics. Therefore, the work of inhibiting damage growth has been carried out in various countries. In our work, an integrated multi-station system is designed to detect and mitigate surface damage on fused silica. The process of processing fused silica optics include UV laser conditioning, surface damage detection and surface damage mitigation with CO2 laser. UV laser conditioning pre-initiates surface damage on fused silica optics with the laser flux less than Laser-Induced Damage Threshold (LIDT). Images of surface damage acquired from camera are processed by improved global threshold segmentation algorithm to extract damage information. Finally, CO2 laser is applied to process the damage with specific morphology to enhance the laser damage resistance. This integrated multi-station system saves the repeated optics installation time between the workstations with the positioning accuracy of 20 μm. Furthermore, the damage with diameter of 10 μm is mitigated to prolong service life of processed fused silica optics. The efficient and accurate integrated multi-station system is of great significance for off -line detecting and mitigating surface damage of fused silica optics in high power laser facility.

Influence of different parameters on nonlinear friction-induced vibration characteristics of water lubricated stern bearings

Lin Chang-Gang,Zou Ming-Song,Zhang Hai-Cheng,Qi Li-Bo,Liu Shu-Xiao 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1

To investigate the mechanism of friction-induced vibration and noise of ship water lubricated stern bearings, a two-degree-of-freedom (2-DOF) nonlinear self-excited vibration model is established. The novelty of this work lies in the detailed analysis of influence of different parameters on the stability and nonlinear vibration characteristics of the system, which provides a theoretical basis for the various friction vibration and noise phenomenon and has a very important directive meaning for low noise design of water lubricated stern bearings. The results reveal that the change of any parameter, such as rotating speed of shaft, contact pressure, friction coefficient, system damping and stiffness, has an important influence on the stability and nonlinear response of the system. The vibration amplitudes of the system increase as (a) rotating speed of shaft, contact pressure, and the ratio of static friction coefficient to dynamic friction coefficient increase and (b) the transmission damping between motor and shaft decreases. The frequency spectrum of the system is modulated by the first mode natural frequency, which is continuous multi-harmonics of the first mode natural frequency. The response of the system presents a quasi-periodic motion.

Joint-transform Correlator Multiple-image Encryption System Based on Quick-response Code Key

Qi Chen,Xueju Shen,Yue Cheng,Fuyu Huang,Chao Lin,HeXiong Liu 한국광학회 2019 Current Optics and Photonics Vol.3 No.4

A method for joint-transform correlator (JTC) multiple-image encryption based on a quick-response (QR) code key is proposed. The QR codes converted from different texts are used as key masks to encrypt and decrypt multiple images. Not only can Chinese text and English text be used as key text, but also symbols can be used. With this method, users have no need to transmit the whole key mask; they only need to transmit the text that is used to generate the key. The correlation coefficient is introduced to evaluate the decryption performance of our proposed cryptosystem, and we explore the sensitivity of the key mask and the capability for multiple-image encryption. Robustness analysis is also conducted in this paper. Computer simulations and experimental results verify the correctness of this method.

A Reliability Model of Wind Farm Considering the Complex Terrain and Cable Failure Based on Clustering Algorithm

Liu, Wenxia,Chen, Qi,Zhang, Yuying,Qiu, Guobing,Lin, Chenghui The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.6

A reliability model of wind farm located in mountainous land with complex terrain, which considers the cable and wind turbine (WT) failures, is proposed in this paper. Simple wake effect has been developed to be applied to the wind farm in mountainous land. The component failures in the wind farm like the cable and WT failures which contribute to the wind farm power output (WFPO) and reliability is investigated. Combing the wind speed distribution and the characteristic of wind turbine power output (WTPO), Monte Carlo simulation (MCS) is used to obtain the WFPO. Based on clustering algorithm the multi-state model of a wind farm is proposed. The accuracy of the model is analyzed and then applied to IEEE-RTS 79 for adequacy assessment.

A Hardware-in-the-loop Platform for Modular Multilevel Converter Simulations

Liu, Chongru,Tian, Pengfei,Wang, Yu,Guo, Qi,Lin, Xuehua,Wang, Jiayu The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

In this paper, a hardware-in-the-loop simulation platform for MMCs is established, which connects a real time digital simulator (RTDS) and a designed MMC controller with optical fiber. In this platform, the converter valves are simulated with a small time step of 2.5 microsecond in the RTDS, and multicore technology is implemented for the controller so that the parallel valve control is distributed between different cores. Therefore, the designed controller can satisfy the requirements of real-time control. The functions of the designed platform and the rationality for the designed controller are verified through experimental tests. The results show that different modulation modes and various control strategies can be implemented in the simulation platform and that each control objective can been tracked accurately and with a fast dynamic response.

Comparison of the Efficacy and Safety of EFGR Tyrosine Kinase Inhibitor Monotherapy with Standard Second-line Chemotherapy in Previously Treated Advanced Non-small-cell Lung Cancer: a Systematic Review and Meta-analysis

Qi, Wei-Xiang,Shen, Zan,Lin, Feng,Sun, Yuan-Jue,Min, Da-Liu,Tang, Li-Na,He, Ai-Na,Yao, Yang Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.10

Purpose: To compare the efficacy and safety of epidermal growth factor receptor tyrosine kinase inhibitormonotherapy (EFGR-TKIs: gefitinib or erlotinib) with standard second-line chemotherapy (single agent docetaxel or pemetrexed) in previously treated advanced non-small-cell lung cancer (NSCLC). Methods: We systematically searched for randomized clinical trials that compared EGFR-TKI monotherapy with standard second-line chemotherapy in previously treated advanced NSCLC. The end points were overall survival (OS), progression-free survival (PFS), overall response rate (ORR), 1-year survival rate (1-year SR) and grade 3 or 4 toxicities. The pooled hazard ratio (HR) or risk ratio (RR), with their corresponding 95% confidence intervals (CI) were calculated employing fixed- or random-effects models depending on the heterogeneity of the included trials. Results: Eight randomized controlled trials (totally 3218 patients) were eligible. Our meta-analysis results showed that EGFR-TKIs were comparable to standard second-line chemotherapy for advanced NSCLC in terms of overall survival (HR 1.00, 95%CI 0.92-1.10; p=0.943), progression-free survival (HR 0.90, 95%CI 0.75-1.08, P=0.258) and 1-year-survival rate (RR 0.97, 95%CI 0.87-1.08, P=0.619), and the overall response rate was higher in patients who receiving EGFR-TKIs(RR 1.50, 95%CI 1.22-1.83, P=0.000). Sub-group analysis demonstrated that EGFR-TKI monotherapy significantly improved PFS (HR 0.73, 95%CI: 0.55-0.97, p=0.03) and ORR (RR 1.96, 95%CI: 1.46-2.63, p=0.000) in East Asian patients, but it did not translate into increase in OS and 1-year SR. Furthermore, there were fewer incidences of grade 3 or 4 neutropenia, febrile neutropenia and neutrotoxicity in EGFR-TKI monotherapy group, excluding grade 3 or 4 rash. Conclusion: Both interventions had comparable efficacy as second-line treatments for patients with advanced NSCLC, and EGFR-TKI monotherapy was associated with less toxicity and better tolerability. Moreover, our data also demonstrated that EGFR-TKImonotherapy tended to be more effective in East Asian patients in terms of PFS and ORR compared with standard second-line chemotherapy. These results should help inform decisions about patient management and design of future trials.