摘要:
It is crucial to correctly predict the S-matrix with plasma and set the optimal impedance matching device in the ion cyclotron resonance heating (ICRH) antenna system design. In this paper, a hybrid circuit/3DLHDAP code to verify the S-matrix measurements in the presence of plasma and optimize the load-resilient conjugate-T circuit for Large Helical Device (LHD) ICRH antennas has been developed and benchmarked. The variation of S-matrices for handshake form (HAS) and field-aligned-impedance-transforming (FAIT) antenna systems with density, magnetic field and coupling distance during heating obtained by the code's simulations agrees with that of with the LHD ICRH experiments. The mutual coupling of toroidally aligned HAS antennas is larger than that of poloidally aligned FAIT antennas over a wide range of densities. When the density and coupling distance increase, under a magnetic field on the magnetic axis of 2.75 T and 1.0 T, within a certain density change range, at the minimum voltage position with vacuum injection, the change rule of the antennas' S-a_minV_ 11 and S-a_minV_ 22 with density is opposite to that with coupling distance, which means that under certain conditions, adjusting the coupling distance may make up for the S-parameters changes caused by plasma density variation, keeping the minimum voltage position fixed, and may make impedance matching easier to achieve during long-pulse operation. Based on obtaining the S parameters, conjugate-T circuits for the HAS and FAIT antennas are designed with the hybrid circuit/3DLHDAP code, which can keep the reflection coefficients low without controlling impedance matching device over a wide range of plasma parameters region. The related results in this paper may provide some guidance for the high-power long-pulse operation of the ICRH antenna system on the fusion device.
通讯机构:
[Wang, Y ] U;Univ South China, Sch Elect Engn, Hunan Prov Key Lab Ultrafast Micro Nano Technol &, Hengyang 421001, Peoples R China.
摘要:
Wireless rechargeable sensor network (WRSN) uses mobile chargers (MCs) to charge sensor nodes wirelessly to solve the energy problems faced by traditional wireless sensor network. In WRSN, mobile charging schemes with multiple MCs supplementing energy are quite common. How to properly plan the MC's moving path to reduce the charge energy loss and deploy nodes to improve network coverage rate has become a huge research challenge. In this paper, a collaborative energy optimization algorithm (CEOA) is proposed for multiple chargers based on k-mean++ and node collaborative scheduling. The CEOA combines internal energy optimization and external device power supply, effectively prolongs network lifetime, and improves network coverage rate. It uses the k-mean++ to cluster nodes in the network; then, the nodes in the network are scheduled to sleep based on the confident information coverage (CIC) model. Finally, the CEOA uses a main mobile charger to carry multiple auxiliary mobile chargers to charge all the nodes in the cluster. Simulation results show that the proposed algorithm increases the network lifetime by more than 8 times and the coverage rate by about 20%.
通讯机构:
[Wang, XZ ; Du, XY; Hao, XT ] S;Shandong Univ, Sch Phys, State Key Lab Crystal Mat, Jinan 250100, Shandong, Peoples R China.;Southern Univ Sci & Technol, Acad Adv Interdisciplinary Studies, Shenzhen 518055, Guangdong, Peoples R China.;Southern Univ Sci & Technol, Dept Mat Sci & Engn, Shenzhen 518055, Guangdong, Peoples R China.;Univ South China, Sch Elect Engn, Hengyang 421001, Peoples R China.
关键词:
exciton dynamics;non-fullerene acceptors;organic solar cells;photovoltaic stability;ultrafast spectroscopy
摘要:
Benefiting from the synergistic development of material design, device engineering, and the mechanistic understanding of device physics, the certified power conversion efficiencies (PCEs) of single-junction non-fullerene organic solar cells (OSCs) have already reached a very high value of exceeding 19%. However, in addition to PCEs, the poor stability is now a challenging obstacle for commercial applications of organic photovoltaics (OPVs). Herein, recent progress made in exploring operational mechanisms, anomalous photoelectric behaviors, and improving long-term stability in non-fullerene OSCs are highlighted from a novel and previously largely undiscussed perspective of engineering exciton and charge carrier pathways. Considering the intrinsic connection among multiple temporal-scale photocarrier dynamics, multi-length scale morphologies, and photovoltaic performance in OPVs, this review delineates and establishes a comprehensive and in-depth property-function relationship for evaluating the actual device stability. Moreover, this review has also provided some valuable photophysical insights into employing the advanced characterization techniques such as transient absorption spectroscopy and time-resolved fluorescence imagings. Finally, some of the remaining major challenges related to this topic are proposed toward the further advances of enhancing long-term operational stability in non-fullerene OSCs.
摘要:
With the wide application of pulsed power technology in tumor ablation, sewage treatment, and other related fields, researchers have found that bipolar electrical pulses are more effective than unipolar electrical pulses. In this article, a new bipolar pulse generator is proposed, which combines the features of boost circuit and Marx circuit to significantly improve the boost ratio of output pulse and the tunability of pulse peak. In order to improve the load regulation rate and peak stability of bipolar pulse power supply, a bipolar pulse power supply based on peak closed-loop control method is designed in this article. The high-voltage pulse is attenuated, and its peak is sampled by the pulse peak sampling circuit, and the pulse peak voltage is fed back to the DSP controller for comparison with the set peak value, and the proportional integral differential (PID) adjustment is performed according to the voltage deviation, and the boost ratio of the pulse generator is changed to realize the constant peak output of the bipolar pulse. In order to verify the feasibility of the proposed bipolar pulse generator with peak closed-loop control scheme, simulation and experimental studies of the bipolar pulse power supply with five-stage peak closed-loop control were conducted. The results show that the output repetition frequency of 5 kHz, pulsewidth of 5– $10~\mu \text{s}$ , and peak pulse value within ±2.0 kV can be stabilized when the input voltage is 100 V.
摘要:
模块化多电平换流器(Modular Multilevel Converters,MMC)具有维护方便,易扩容等优点,在柔性直流输电(High Voltage Direct Current,HVDC)、电网谐波治理等领域得到广泛应用。但其子模块中的分散电容,在实际使用中会产生谐波环流,影响了模块电容电压波动,降低换流器的安全裕度和经济性。文章首先介绍了MMC组成结构;然后通过建立桥臂瞬时功率方程,分析环流产生机理,并得出桥臂环流中存在二次谐波分量的结论,通过控制直流侧电压与桥臂等效输出电压之间的差值,调节环流中的谐波分量,进而将现阶段国内、外环流抑制方法分为间接环流抑制方法与直接环流抑制方法,并对环流的利用也做了相关阐述。最后对环流抑制存在的问题进行总结与展望。
摘要:
High concentration of Er3+/Yb3+ co‐doped WS2 monolayer is creatively prepared by in‐situ chemical vapor deposition technique. The performances of the devices (photodetectors and field‐effect transistors) are significantly enhanced after rare‐earth (RE) co‐doping, which can be attributed to the stronger light absorption and higher the transitions of electronic states, providing an excellent strategy for practical application in optoelectronics. Abstract Chemical doping is a significant means to modulate bandgap structures and optoelectronic properties of transition metal dichalcogenides (TMDCs). Herein, an Er3+/Yb3+ co‐doped WS2 monolayer with ultrahigh and tunable concentrations is successfully fabricated by in‐situ chemical vapor deposition (CVD) technique. The morphologies, thicknesses, components, and structures of the samples are systemically characterized by optical microscope, atomic force microscopy, Raman, X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscope with energy dispersive spectrometer, and high‐resolution transmission electron microscopy, respectively. Photoluminescent peaks are enhanced significantly with red shifts, and the absorption is broadened to near‐infrared, implying a shrinked bandgap after RE co‐doping, which is consistent to the calculation results by density functional theory (DFT). The Er3+/Yb3+ co‐doped WS2 device demonstrates high carrier mobility, photocurrent, photoresponsivity, external quantum efficiency, and specific detectivity, which are approximately two orders of magnitudes compared with those of the pristine WS2 device. The values of photoresponsivity and specific detectivity approach 4.8 × 104 A W−1 and 5.5 × 1014 Jones, respectively, at 20 V bias and 1.77 mW cm−2 luminescence, which may refresh the records as has been reported. The excellent performances of the WS2 photodetector prove the effectiveness of Er3+/Yb3+ co‐doping for practical application in optoelectronics.
作者机构:
[Liu, Yong] Univ South China, Coll Elect Engn, Hengyang 421001, Peoples R China.;[Hu, Ji-wen; Xie, Ya-qian; Liu, Yong] Univ South China, Coll Math & Phys, Hengyang 421001, Peoples R China.
会议名称:
Conference on Biophysical-Society-of-GuangDong-Province-Academic-Forum - Precise Photons and Life Health (PPLH)
会议时间:
DEC 09-11, 2022
会议地点:
Guangzhou, PEOPLES R CHINA
会议主办单位:
[Liu, Yong] Univ South China, Coll Elect Engn, Hengyang 421001, Peoples R China.^[Liu, Yong;Hu, Ji-wen;Xie, Ya-qian] Univ South China, Coll Math & Phys, Hengyang 421001, Peoples R China.
会议论文集名称:
Proceedings of SPIE
关键词:
Atherosclerosis;Electromagnetic wave;Ablation of heat;Finite element method
摘要:
The purpose of this study is to explore the thermal damage of microwave to atherosclerotic plaques in order to achieve the purpose of treating atherosclerosis. In this paper, a fluid-solid-heat coupling model of thermal ablation of atherosclerotic plaque is established (The coupling model of blood-plaque-electromagnetic wave is studied in this paper, in which the thermal ablation of atherosclerotic plaque means that the electromagnetic wave is used to generate heat, and the temperature of atherosclerotic plaque tissue rises. If the cells in it reach the threshold of death temperature, they will be killed, so as to achieve the purpose of thermal ablation.). The electromagnetic field and bio-thermal equation are solved and analyzed by finite element method. By calculating the temperature and thermal damage distribution of microwave on atherosclerotic plaque, the effect of microwave on thermal ablation of atherosclerotic plaque was evaluated. The results show that the thermal damage degree of atherosclerotic plaque is positively correlated with electromagnetic wave frequency, electromagnetic wave power and heating time. The model shows that electromagnetic wave hyperthermia may provide a new therapeutic mode for thermal ablation of atherosclerotic plaques.
摘要:
At present, system-level fault detection and diagnosis (FDD) research often uses correlation-based machine learning methods combined with multiple heterogeneous diagnosis methods to improve the fault detection rate (FDR), that is, decision-level fusion. Since it does not take into account the causal direction of the decision relationship, it will affect the realization of the fusion objectives, and lead to the reduction of the fusion range and the decrease of the global decision on FDR. In this regard, the structural causal model (SCM), a commonly used causal model in causal science, can use the causal graph to ensure causal direction of fusion, and the structural equation can be used to achieve fusion objectives to increase FDR, which can improve this problem. In this paper, we propose seven fusion objectives according to the diagnostic advantage interval of each preliminary method, and use SCM to construct causal graph and structural equation to achieve decision-level fusion according to the proposed seven fusion objectives, thereby improving FDR. The proposed method is validated through the simulation platform Tennessee Eastman process. We choose to combine the prediction results of Linear Discriminant Analysis method and Gaussian Naive Bayes method to achieve decision-level fusion. The results show that compared with the single method and the Bayesian network decision-level fusion method, the proposed method can achieve the best results in the FDR of each single system state and average FDR, and the above indicators are significantly improved.
作者机构:
[Lu, Zhendong; Luo, Xiao-Qing; Liu, Qin-Ke; Luo, XQ; Zhou, Yaojie; Wang, Xin-Lin] Univ South China, Sch Elect Engn, Hengyang 421001, Peoples R China.;[Li, Yan] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Liu, W. M.] Chinese Acad Sci, Inst Phys, Beijing Natl Lab Condensed Matter Phys, Beijing 100190, Peoples R China.;[Wang, Xin-Lin] Univ South China, Sch Mech Engn, Hunan Prov Key Lab Ultrafast Micro Nano Technol &, Hengyang 421001, Peoples R China.
通讯机构:
[Luo, XQ ] U;Univ South China, Sch Elect Engn, Hengyang 421001, Peoples R China.
摘要:
Chiral metasurfaces, with appealing properties for studying light-matter interactions at the nanoscale, have emerged as a promising platform for the realization of chiral optical responses, thereby showing advantages in chirality-related applications. The conventional approaches primarily concentrate on circular dichroism and the high Q factor of the chiral resonances, while little attention has been paid to the aspects of flexibility and controllability in the modulation of optical chirality, further inhibiting the implementation of tunable and multifunctional chiral metadevices. Here, we employ a planar chiral silicon metasurface governed by bound states in the continuum (BICs) to unravel steerable chiral optical responses. In particular, the BIC-based intrinsic and extrinsic planar chiralities can be precisely steered by breaking the in-plane symmetry and the illumination symmetry, respectively. Moreover, a hybrid Si−VO2 metasurface, manifested by the chiral coupled-mode theory, showcases the feasibility of actively tuning the dissipative loss while maintaining chiral quasi-BICs, then yielding desired loss-steered optical chirality. Our results provide alternative insights into tunable optical chirality and pave the way for advancements in chiroptical applications.
摘要:
Two-dimensional (2D) GeSe has been proven promising in fast and broadband optoelectronic applications for its complicated band structure, inert surface property, and excellent stability. The major challenge is the deficiency of the effective technique for controllably prepared large-scale few-to-monolayer GeSe films. For this purpose, a layer-by-layer thinning method by thermal sublimation for manufacturing large-scale mixed few-layer GeSe with direct bandgaps is proposed, and an optimized sublimation temperature of 300 °C in vacuum is evaluated by atomic force microscopy. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectra, and fluorescence mapping measurements are performed on the thinned GeSe layers, and results are well-indexed to the orthorhombic lattice structure with direct bandgaps with an atomic ratio of Ge/Se ≈ 5:4. Raman and fluorescence spectra show an α-type crystalline structure of the thinned GeSe films, indicating the pure physical process of the sublimation thinning. Both the bulk and few-layer GeSe films demonstrate broadband absorption. Conductivity of the few-layer GeSe device indicates the overall crystalline integrity of the film after thermal thinning. Given the convenience and efficiency, we provide an effective approach for fabrication of large-scale 2D materials that are difficult to be prepared by traditional methods.