排序方式: 共有112条查询结果,搜索用时 156 毫秒
21.
张继县 《光谱学与光谱分析》1992,12(1):108-110
火焰原子吸收测定人发中Ca,当加入锶盐为释放剂时,经实验得知:样品需稀释500倍以上方能得出正确的结果。 相似文献
22.
M. A. Pedrosa C. Hidalgo A. López-Fraguas B. Ph. Van Milligen R. Balbín J. A. Jiménez E. Sánchez J. Castellano TJ-II Team L. García B. A. Carreras V. E. Lynch 《Czechoslovak Journal of Physics》2000,50(12):1463-1470
It has been shown that transport barriers in toroidal magnetically confined plasmas tend to be linked to regions of unique
magnetic topology such as the location of a minimum in the safety factor, rational surfaces or the boundary between closed
and open flux surfaces. In the absence ofE×B sheared flows, fluctuations are expected to show maximum amplitude near rational surfaces, and plasma confinement might tend
to deteriorate. On the other hand, if the generation ofE×B sheared flows were linked to low order rational surfaces, these would be beneficial for confinement. Experimental evidence
ofE×B sheared flows linked to rational surfaces has been obtained in the plasma edge region of the TJ-II stellarator.
Presented at the Workshop on the Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June, 2000. 相似文献
23.
Jakubowski MW Schmitz O Abdullaev SS Brezinsek S Finken KH Krämer-Flecken A Lehnen M Samm U Spatschek KH Unterberg B Wolf RC;TEXTOR Team 《Physical review letters》2006,96(3):035004
The magnetic-field perturbation produced by the dynamic ergodic divertor in TEXTOR changes the topology of the magnetic field in the plasma edge, creating an open chaotic system. The perturbation spectrum contains only a few dominant harmonics and therefore it can be described by an analytical model. The modeling is performed in the vacuum approximation without assuming a backreaction of the plasma and does not rely on any experimentally obtained parameters. It is shown that this vacuum approximation predicts in many details the experimentally observed plasma structure. Several experiments have been performed to prove that the plasma edge behavior is defined mostly by the magnetic topology of the perturbed volume. The change in the transport can be explained with the knowledge of only the magnetic structures; i.e., the ergodic pattern dominates the plasma properties. 相似文献
24.
25.
Thermal decomposition of zinc carbonate hydroxide 总被引:3,自引:0,他引:3
N. Kanari D. Mishra I. Gaballah B. Dupr Mineral Processing Environmental Engineering Team 《Thermochimica Acta》2004,410(1-2):93-100
This study is devoted to the thermal decomposition of two zinc carbonate hydroxide samples up to 400 °C. Thermogravimetric analysis (TGA), boat experiments and differential scanning calorimetry (DSC) measurements were used to follow the decomposition reactions. The initial samples and the solid decomposition products were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and laser particle size analyzer. Results showed that zinc carbonate hydroxide decomposition started at about 150 °C and the rate of decomposition became significant at temperatures higher than 200 °C. The apparent activation energies (Ea) in the temperature range 150–240 °C for these two samples were 132 and 153 kJ/mol. The XRD analyses of the intermediately decomposed samples and the DSC results up to 400 °C suggested a single-step decomposition of zinc carbonate hydroxide to zinc oxide with not much change in their overall morphologies. 相似文献
26.
Slide-away discharges are achieved by decreasing the plasma density or ramping down the plasma current in runaway discharges in the HT-7 tokamak. In the case of plasma current ramp down, the ratio of the electron plasma frequency to the electron cyclotron frequency is higher than in the stationary pulses when the discharge goes into a slide-away regime. The instability regime is characterized by relaxations in the electron cyclotron emission due to relativistic anomalous Doppler effect which transfers energy from parallel to perpendicular motion. The triggering of relativistic anomalous Doppler effect at higher density by ramping down of plasma current may provide a alternative runaway energy control scenario. 相似文献
27.
在一系列H模放电条件下,建立了一个旨在研究等离子体温度分布剖面不变性的数据库。介绍了数据库建立过程中要解决的关键问题和所用软件,对等离子体温度分布剖面不变性及芯部约束与边缘参数的关系进行了研究。 相似文献
28.
Giruzzi G Imbeaux F Ségui JL Garbet X Huysmans G Artaud JF Bécoulet A Hoang GT Litaudon X Maget P Saoutic B;Tore Supra Team 《Physical review letters》2003,91(13):135001
During noninductively driven discharges in the Tore Supra tokamak, steady sinusoidal oscillations of the central electron temperature, lasting as long as 2 min, have been observed for the first time. Having no helical structure, they cannot be ascribed to any known MHD instability. The most plausible explanation of this new phenomenon is that the plasma current density and the electron temperature evolve as a nonlinearly coupled predator-prey system. This interpretation is supported by the numerical solution of coupled resistive current diffusion and heat transport equations. 相似文献
29.
Fast, high resolution multichannel Thomson scattering is used to quantitatively determine plasma perturbations induced by type-I edge-localized modes (ELMs) in the low-field side edge of ASDEX Upgrade H-mode plasmas. 2D snapshots of temperature and density, deduced from the laser light scattered in a vertically elongated, poloidal array of 5 x 10 scattering volumes, are obtained in the hot, steep edge gradient zone, which is difficult to access by other diagnostics. Local maxima and minima with large amplitude are identified during ELMs and even in the precursor phase, both in density and temperature. Interpreting these structures as footprints of approximately field aligned helical modes in accordance with previous experimental and theoretical work, toroidal mode numbers between 8 and 20 are obtained, roughly consistent with corresponding scrape-off layer and divertor measurements. 相似文献
30.
The spatial and temporal structures of magnetic signal in the tokamak ADITYA is analysed using recently developed singular
value decomposition (SVD) technique. The analysis technique is first tested with simulated data and then applied to the ADITYA
Mirnov coil data to determine the structure of current peturbation as the discharge progresses. It is observed that during
the current rise phase, current perturbation undergoes transition from m=5 poloidal structure to m=4 and then to m=3. At the time of current termination, m=2 perturbation is observed. It is observed that the mode frequency remains nearly constant (≈10 kHz) when poloidal mode structure
changes from m=4 to m=2. This may be either an indication of mode coupling or a consequences of changes in the plasma electron temperature and
density scale length. 相似文献