Long Pulse Discharges on the HT-7 Superconducting Tokamak

liqun HU 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III

The exploration of high-performance plasma operation under steady-state conditions and relevant physics is the main purpose of the medium-sized superconducting tokamak device HT-7. The key issues in pursuing such a study are wall recycling, high impurity radiation, and MHD instability. Since the last APFA conference in 2003, several important technical modifications have been made on HT-7 for longer sustained plasma operation with high-integrated performance. Except for two poloidal limiters and one inner toroidal belt limiter, new toroidal double-ring graphite limiters located at the top and bottom of the inner wall were adopted in 2004 for steady-state plasma operation; these were actively water-cooled and made of special doped graphite coated with SiC film. Based on the understanding of plasma surface interaction and combing with good wall boronization and conditioning by means of RF-produced plasmas, nearly full non-inductive current driven plasma (Ip = 120 . 180 kA, Bt = 1.5 . 2.0 T, Te(0) = 2 . 4 keV, and ne(0) = (1.0 . 2.5) × 1019 m.3) was achieved by LHCD with a duration of up to 10 s. For lower-performance operation (Ip = 55 kA, Te(0) 1.0 keV, and central ne(0) = (0.7 . 1.0) × 1019 m.3), reproducible long-pulse discharges with operational duration of up to 240 s were sustained by the LHCD (<200 kW), in almost steady-state condition.

Preparation and Drug Release Behavior of Tussah Silk Fibroin Composite Membrane

Zhuang Hu,Kaixia An,Jia Wang,Xiaoxu Xu,Zhangpei Chen,Jianshe Hu,Liqun Yang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.2

Silk fibroin (SF) aqueous solution was obtained by the degumming and dissolution of tussah silk, and then the obtained solution was chemically cross-linked with sodium alginate (SA) to form composite membrane, which could be used as a carrier for sustained drug release. The mechanical properties and dissolution rate of such composite membrane togetherwith the drug release behavior under different conditions were investigated. A series of structure-tunable composite membranes were prepared through altering the ingredients proportion, the pH value during fabrication, the concentration of Ca2+, and cross-linking time. The drug release behavior of the corresponding drug-loaded composite membrane was elaborate studied using artemisinin as the model drug. It was found that the drug release rate exhibited a decreasing trend with increasing the SF content, the Ca2+ concentration and the cross-linking time of the corresponding composite membrane. Moreover, the drug release behavior exhibited pH sensitivity, and the drug release rate could be promoted under weak alkaline conditions.

FOXK1 regulates epithelial-mesenchymal transition and radiation sensitivity in nasopharyngeal carcinoma via the JAK/STAT3 signaling pathway

Duan Liqun,Huang Jinlong,Zhang Yong,Pi Guoliang,Ying Xiaofang,Zeng Fanyu,Hu Desheng,Ma Jia 한국유전학회 2023 Genes & Genomics Vol.45 No.6

Background Nasopharyngeal carcinoma (NPC) is the most common head and neck tumor in China. Forkhead box (FOX) proteins have 19 subfamilies, which can maintain cell metabolism, regulate cell cycle and cell growth, etc. FOXK1 is a member of the FOX family, and studies have found that FOXK1 is closely related to tumors. Objective This experiment aims to study the effects of FOXK1 interference on proliferation, apoptosis, invasion, epithelial-mesenchymal transition (EMT), and radiosensitivity, by regulating the Janus kinas/signal translator and activator of the transfer 3 (JAK/STAT3) pathway. Methods The expression of FOXK1 was detected via immunohistochemistry using clinical nasopharyngeal carcinoma tissues and adjacent tissues. The relationship between FOXK1 expression and tumor stage was subsequently evaluated. The colony formation rate was calculated through the colony formation experiment. Cell apoptosis and cell cycle distribution were detected using flow cytometry, while cell invasion was detected using the Transwell method. The number of cells in the nucleus of each group after 30 min, 4 h, and 24 h of radiotherapy with the 2 Gy dose was counted using immunofluorescence under γ-H2AX focal points of a laser confocal microscope. Results FOXK1 is clearly expressed in the patients’ cancer tissues. The expression of FOXK1 was significantly correlated with the patient’s sex. FOXK1 interference or Peficitinib can upregulate the apoptosis rate of 5-8 F and CNE-2 cells; increase the G2 phase of cells; and inhibit the invasion, migration, and EMT of cells. At the same time, FOXK1 interference can downregulate the protein expression of p-JAK1, p-JAK2, and p-STAT3 in cells. Interference from FOXK1 or Peficitinib alone can reduce the rate of cell colony formation under different radiation doses, and enhance the green fluorescence intensity of γ-H2AX in the nucleus after 4 and 24 h of the 2 Gy dose of radiotherapy. These results are optimal when FOXK1 interference and Peficitinib are used together. Conclusion FOXK1 interference in NPC cells can regulate EMT through the JAK/STAT3 signal pathway, enhance the radiosensitivity of cells, and thus inhibit tumor cell progression.

Fishbone Oscillations in the Experimental Advanced Superconductivity Tokamak

Liqing Xu,Liqun Hu,Yi Yuan,Yingying Li,Guo-Qiang Zhong,Hai-Qing Liu,Kaiyun Chen,Tong-Hui Shi,Yan-Min Duan 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.6

A fishbone oscillation was observed in the neutral beam injection plasma at Experimental Ad- vanced Superconductivity Tokamak (EAST). This m = 1/n = 1 (m, n: poloidal, toroidal mode numbers, respectively) typical internal kink mode travels in the ion-diamagnetism direction in the poloidal section with a rotation speed close to the ion diamagnetic drift frequency. A high thermal plasma beta and high amounts of energetic ions are necessary for the mode to develop. Fishbone oscillations can expel heavy impurities in the core, which favors sustaining a high-performance plasma. The born frequency of the fishbone oscillation is the ion diamagnetic drift frequency and the chirping down of the frequency during the initial growth phase is the result of a drop in ion- diamagnetic drift frequency. The excitation energy is thought to be due to the thermal plasma pressure gradient; however, the development of a fishbone oscillation is related to energetic ions. A fishbone oscillation was observed in the neutral beam injection plasma at Experimental Advanced Superconductivity Tokamak (EAST). This m = 1/n = 1 (m, n: poloidal, toroidal mode numbers, respectively) typical internal kink mode travels in the ion-diamagnetism direction in the poloidal section with a rotation speed close to the ion diamagnetic drift frequency. A high thermal plasma beta and high amounts of energetic ions are necessary for the mode to develop. Fishbone oscillations can expel heavy impurities in the core, which favors sustaining a high-performance plasma. The born frequency of the fishbone oscillation is the ion diamagnetic drift frequency and the chirping down of the frequency during the initial growth phase is the result of a drop in ion- diamagnetic drift frequency. The excitation energy is thought to be due to the thermal plasma pressure gradient; however, the development of a fishbone oscillation is related to energetic ions.

Static Output-feedback Controller Synthesis for Positive Systems under ℓ∞ Performance

Xiaoming Chen,Mou Chen,Liqun Wang,Jun Shen,Jiapan Hu 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.11

This paper investigates the ℓ∞-induced output-feedback controller synthesis problem for discrete-time positive systems. For positive linear systems, a necessary and sufficient condition for stability and ℓ∞-induced performance is first put forward using a group of linear inequalities. Then, on the basis of these inequalities, theconditions on which static output-feedback controllers exist are set up, and to solve these conditions, a method of iterative convex optimization is provided. Moreover, a complete solution to the synthesis problem of the controller is proposed based on linear programming for positive systems with single output or input. Finally, two examples are presented to illustrate and verify the effective and applicable methods derived in this paper.

Transient Snakes in an Ohmic Plasma Associated with a Minor Disruption in the HT-7 Tokamak

Songtao Mao,Liqing Xu,Liqun Hu,Kaiyun Chen 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.9

A transient burst (2 ms, an order of the fast-particle slowdown timescale) of a spontaneous snakeis observed for the first time in a HT-7 heavy impurity ohmic plasma. The features of the low-Zimpurity snake are presented. The flatten electron profile due to the heavy impurity reveals theformation of a large magnetic island. The foot of the impurity accumulation is consistent with thelocation of the transient snake. The strong frequency-chirping behaviors and the spatial structuresof the snake are also presented.

Long-lived Impurity-ion Snakes in the EAST ELM-free H-mode Sawtoothing Plasma

Tianpeng Ma,Liqing Xu,Liqun Hu 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.11

Two types of long-lived impurity-ion snakes (LLSs) including the ideal-like kink mode which damps before the large sawtooth crash, termed sawtooth-free LLSs (SF-LLSs) and complex LLSs (C-LLSs), which coexist with compound sawtooth and final damping after sawtooth crash were observed in EAST ELM-free H-mode sawtoothing plasma. These LLSs have an m = 1 structure, accompanied by several harmonic modes (m = 2, m = 3 . . .). There is a slight frequency-chirping behavior of the LLS. Similar with the typical sawtooth crash phase, a large crescent-shaped helical island-like structure in the core region of the C-LLSs was visible after the major crash of the coexisting compound sawtooth. The strong coupling of the C-LLSs and the 2/1 tearing mode (TM) can trigger a neo-classical tearing mode (NTM) due to a forced magnetic reconnection.

Stability of the m/n=1/1 mode during the ramp phase of the sawtooth oscillations at different phase angles of the lower hybrid wave on the HT-7 tokamak

youwen Sun,Baonian Wan,Biao Shen,Bojiang Ding,Haiqing Liu,Jinping Qian,Liqun Hu,Zhongyong Chen 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III

The stability of the m/n = 1/1 mode (named “mid-oscillation”) during the ramp phase of the sawtooth oscillations in different current profiles has been investigated in a recent experiment. Modification of the local current density profile in the central region was obtained by changing the spectrum of the parallel refractive index Nk of the lower hybrid wave (LHW) with other parameters fixed. This shows that the amplitude and the growth rate of the mid-oscillation decrease with increasing peak value of the parallel refractive index Npeak k and the mode disappears during most of the sawtooth rampphases when Npeak k 3.15. This result directly demonstrates that the mode is mainly destabilized by the local current density gradient

Recent Advances of Scintillator-Based Escaping Fast Ion Diagnostics in Toroidal Fusion Plasmas in Japan, Korea, and China

Isobe, Mitsutaka,Kim, Junghee,Zhang, Yipo,Chang, Jiafeng,Ogawa, Kunihiro,Kim, Jun Young,Liu, Yi,Hu, Liqun AMERICAN NUCLEAR SOCIETY, INC. 2017 Fusion science and technology Vol.72 No.1