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Selective laser melting is a new manufacturing technique that can easily facilitates metal parts with complex structural shapes and high performance. This paper processed 316L stainless steel by SLM technology, and characterized the microstructure and mechanical properties of the as-built specimen. The complex microstructure with cells and columnar grains was observed in the specimen, the specimen density is about 97% and the hardness can reach 189 HV. The wear test results show that the average friction coefficient of the SLM sample is 0.642.Selective laser melting is a new manufacturing technique that can easily facilitates metal parts with complex structural shapes and high performance. This paper processed 316L stainless steel by SLM technology, and characterized the microstructure and mechanical properties of the as-built specimen. The complex microstructure with cells and columnar grains was observed in the specimen, the specimen density is about 97% and the hardness can reach 189 HV. The wear test results show that the average friction coefficient of the SLM sample is 0.642.

In this study, we collected 20 Tibet Rubus taxa from 4 sections, Idaeobatus, Malachobatus, Chamaebatus, and Cylactis of genus Rubus, as well as two outgroups, Fragaria vesca and Rosa banksiae. To investigate the phylogenetic relationships among Tibet Rubus species, the phylogeny was reconstructed by using chloroplast rbcL, rpl20-rps12, and trnG-trnS, nuclear ITS, GBSSI-2 and PEPC sequences. The final combined chloroplast DNA matrix consisted of 22 taxa and 2124 bp, of which 204 (9.60%) were variable and 94 (4.43%) parsimony informative. The nuclear DNA dataset included 22 accessions and 1897 aligned nucleotides that contained 374 (19.72%) variable and 146 (7.70%) parsimony informative sites. TIM1+I+G and TrN+G were selected as the best-fit models for the combined chloroplast and nuclear datasets, respectively. The Tibet Rubus is resolved as a monophyletic group and well supported through both chloroplast and nuclear datasets. Sect. Idaeobatus species have at least two independent evolutionary routes. Two sect. Malachobatus species clustered together with high support values. Then they were sister to three sect. Cylactis species in chloroplast tree, while to the subclade of major sect. Idaeobatus species in nuclear tree. This could be interpreted by frequent hybridization and genetic introgression. Rubus calycinus of sect. Chamaebatus forms a separate clade, suggesting its monophyly. To be concluded, the combined chloroplast and nuclear DNA sequences provided abundant information for the phylogenetic relationships among Tibet Rubus species.

Polyimide(PI), with its great thermal and mechanical properties, has been widely used in various fields, such as aerospace and microelectronics. However, with the development of high technology, common PI materials can not satisfy the demands, due to its high resistance. In this work, we used 2,2’- Bis(trifluoromethyl) benzidine(TFMB) to functionalize GO and further form GO-TFMB/PI nanocomposite film. In the end, we got GO-TFMB/PI nanocomposite films with excellent thermal stability, better toughness and better electrical conductivity. As shown in results, the incorporation of GO-TFMB maintained excellent thermal stability. With the addition of GO-TFMB, the resistivity of the composite film decreased continuously. And when the content of GO-TFMB was 0.8 wt%, the resistivity could achieve the excellent antistatic material standard.

This paper presents a comprehensive emergency power control strategy for AC/DC hybrid power systems containing VSC-HVDC. Firstly, the paper analyzes the power support of the VSC-HVDC to the AC lines using the Power Transferring Relativity Factor (PTRF). Then the power adjustment of the VSC-HVDC in several different circumstances are calculated. Finally, the online power control strategies of VSC-HVDC are designed, which could rapidly control the power of the VSC-HVDC, keeping the power flow of AC lines below the upper limit. Furthermore, the strategy is proven to be effective by the simulations with EMTDC/PSCAD.

Under the background of building global energy interconnection and achieving green and low-carbon development, this paper grasps a new round of energy restructuring and the trend of energy technology change, based on the present situation of global and China’s global energy interconnection development, established the index system of the impact of global energy interconnection development factors. A subjective and objective weight analysis of the factors affecting the development of the global energy interconnection was conducted separately by network level analysis and entropy method, and the weights are summed up by the method of additive integration, which gives the comprehensive weight of the influencing factors and the ranking of their influence.Under the background of building global energy interconnection and achieving green and low-carbon development, this paper grasps a new round of energy restructuring and the trend of energy technology change, based on the present situation of global and China’s global energy interconnection development, established the index system of the impact of global energy interconnection development factors. A subjective and objective weight analysis of the factors affecting the development of the global energy interconnection was conducted separately by network level analysis and entropy method, and the weights are summed up by the method of additive integration, which gives the comprehensive weight of the influencing factors and the ranking of their influence.

An Eulerian–Lagrangian computational model for simulations of gas-liquid flows in a continuous casting mold is developed. The flow of the fluid phase is solved in an Eulerian frame of reference together with the motion of every individually injected gas bubble, solved in its own Lagrangian frame of reference. It is assumed that the gas bubbles remain spherical and their shape variations are neglected. In order to consider the bidirectional interactions between the bubbles and the melt flow two different methods (the one-way coupling and the two-way coupling) are studied and compared. The simulations show that the two-way coupling is essential to get realistic results.

Definition of raceway shape and size has always been a challenging task. In this study, based on physical simulation of the COREX melter gasifier, the pictures near the raceway zone are recorded by a high speed camera and the particles velocity contours are analyzed. Then three progressive methods are developed to describe the raceway size under different blowing rates. In the first method, the raceway depth and height are determined qualitatively through judging the particles velocity contours; In the second method, the fractal dimensions of different particles velocity contours are obtained by using fractal theory, then the two-dimension raceway depth and height are defined through analyzing the fractal dimensions; In the third method, the surface area of three-dimension ellipsoidal raceway is obtained by using the law of additive codimensions and the fractal dimensions which are from the second method. Due to the same data is used by the three methods, different raceway sizes are obtained, but the general trend is similar and the raceway size from all methods increase with the increasing of blowing rate.

The two sequencing batch reactors (SBRs) were operated to investigate the different effect of Ca2+ and Mg2+ augmentation on aerobic granulation. R1 was augmented with Ca2+ at 40 mg/L, while Mg+ was added to R2 with 40 mg/L. Results indicated that R1 had a faster granulation process, and aerobic granulation reached the steady state after 60 cycles in R1 but 80 cycles in R2. The mean diameter of the mature granules in R1 was 1.6 mm which was consistently larger than that (0.8 mm) in R2, and aerobic granules in R1 also showed a higher physical strength. However, the mature granules in R2 had the higher production yield of polysaccharides and proteins, and aerobic granules in R2 experienced a faster substrate biodegradation. Microbial and genetic characteristics in mature granules were analyzed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results revealed that Mg2+ addition led to higher microbial diversity in mature granules. In addition, the uncult...

A271 ELECTRON CYCLOTRON CURRENT DRIVE IN DIII-D: EXPERIMENT AND THEORY. Experiments on the DIII-D tokamak in which the measured off-axis electron cyclotron current drive has been compared systematically to theory over a broad range of parameters have shown that the Fokker-Planck code CQL3D provides an excellent model of the relevant current drive physics. This physics understanding has been critical in optimizing the application of ECCD to high performance discharges, supporting such applications as suppression of neoclassical tearing modes and control and sustainment of the current profile.

Lorentz gas model is used to examine collisionality modification of the trapped electron effects on electron cyclotron current drive efficiency. Appreciable collisionality enhancement of the current drive efficiency appears to be possible in the strong trapping cases in present-day current drive experiments.

Increased efficiency of off-axis electron cyclotron current drive (ECCD) has been obtained in discharges in DIII-D with higher electron beta, and these results have been understood by studying computationally the particle fluxes in velocity space driven by the EC waves. The relativistic cyclotron resonance tends to shift away in velocity space from the trapped-passing boundary for low-field-side launch as the electron temperature and/or density rise, increasing the net efficiency toward that of the trapping-free Fisch-Boozer level. Calculations with the CQL3D Fokker-Planck code illustrate clearly that the flux in velocity space due to rf-induced diffusion moves away from the trapping boundary for values of βe which have been realized in the experiments.

A local representation is used to determine localized features in the current profiles due to ECCD in the DIII-D tokamak discharges from equilibrium reconstruction based on spectroscopic and external magnetic measurements. Initial results indicate that reconstruction using a local basis function can resolve very peaked ECCD profiles. The reconstructed narrow ECCD profiles are consistent with the quasi-linear Fokker-Planck results from the CQL3D code.

Electron cyclotron current drive (ECCD) experiments on the DIII-D tokamak are solidifying the physics basis for localized, off-axis current drive in both standard and advanced operating modes, the goal being to validate a predictive model for ECCD. The measured ECCD efficiency is found to be in agreement with theoretical calculations using the CQL3D Fokker-Planck code over a range of toroidal injection angles, absorption radii, and electron beta. The latter dependence is especially important since the ECCD efficiency is shown to increase with local electron beta, which is favorable for current profile control using off-axis ECCD in high-beta advanced tokamaks.

Plasma rotation has many beneficial effects on tokamak operation including stabilization of MHD and microturbulence to improve the beta limit and confinement. Contrary to present-day tokamaks, neutral beams may not be effective in driving rotation in fusion reactors; hence the investigation of radiofrequency (RF) induced plasma rotation is of great interest and potential importance. This paper reviews the experimental results of RF induced rotation and possible physical mechanisms, suggested by theories, to explain the observations. This subject is only in the infancy of its research and many challenging issues remained to be understood and resolved.

In plasmas with toroidal rotation, the ions are pushed towards the low-field side of the torus by the centrifugal force. An electrostatic potential is set up to maintain charge neutrality which tends to attract electrons towards the low-field side of the torus. Due to this electrostatic potential, the trapped/passing boundary in the electron velocity space changes from a cone for stationary plasmas to an hyperboloid in a rotating plasma. This reduces the phase space for passing electrons. This paper attempts to address rotation effects on the electron cyclotron current drive efficiency.

A velocity-space connection formula is proposed to estimate the collisionality effect on electron cyclotron current drive efficiency. The collisionality correction gives modest improvement in agreement between theoretical and recent DIII-D experimental results

In a variety of discharge conditions on DIII-D it is observed that rf electron heating reduces the toroidal rotation speed and core ion temperature. The rf heating can be with either fast wave or electron cyclotron heating and this effect is insensitive to the details of the launched toroidal wavenumber spectrum. To date all target discharges have rotation first established with co-directed neutral beam injection. A possible cause is enhanced ion momentum and thermal diffusivity due to electron heating effectively creating greater anomalous viscosity. Another is that a counter directed toroidal force is applied to the bulk plasma via rf driven radial current.

The power deposition profiles for different poloidal and toroidal launch angles have been determined by modulating the ECH power and measuring the electron temperature response. The peak of the measured power density follows the poloidal steering of the ECH launcher, and perpendicular launch gives a narrower deposition profile than does oblique (current drive) launch. The difference in wave refraction between X-mode and O-mode allows positive identification of an unwanted O-mode component of the launched beam.

Neoclassical tearing modes are found to limit the achievable beta in many high performance discharges in DIII-D. Electron cyclotron current drive within the magnetic islands formed as the tearing mode grows has been proposed as a means of stabilizing these modes or reducing their amplitude, thereby increasing the beta limit by a factor around 1.5. Some experimental success has been obtained previously on Asdex-U. Here we examine the parameter range in DIII-D in which this effect can best be studied.

In spherical tokamaks (ST), the magnetic field strength varies over a wide range across the plasma, and at high betas it deviates significantly from the 1/R dependence of conventional tokamaks. This, together with the high density expected in ST, poses challenging problems for RF heating and current drive. In this paper, the authors investigate the various possible applications of fast waves (FW) in ST. The adjoint technique of calculating current drive is implemented in the raytracing code CURRAY. The applicability of high harmonic and subharmonic FW to steady state ST is considered. They find that high harmonic FW tends to be totally absorbed before reaching the core and may be considered a candidate for off axis current drive while the subharmonic FW tends to be absorbed mainly in the core region and may be considered for central current drive. A difficult problem is the maintenance of current at the startup stage. In the bootstrap ramp-up scenario, the current ramp-up is mainly provided by the bootstrap current. Under this condition, the role of rf becomes mainly the sustainment of plasma through electron heating. Using a slab full-wave code SEMAL, the authors find that the ion-ion-hybrid mode conversion scheme is a promising candidate. The effect of possible existence of edge Alfven resonance and high harmonic cyclotron resonance is investigated and regimes of minimization of edge heating identified.

The physics of non-inductive current drive and current profile control using the fast magnetosonic wave has been demonstrated on the DIII-D tokamak. In non-sawtoothing discharges formed by neutral beam injection (NBI), the radial profile of the fast wave current drive (FWCD) was determined by the response of the loop voltage profile to co, counter, and symmetric antenna phasings, and was found to be in good agreement with theoretical models. The application of counter FWCD increased the magnetic shear reversal of the plasma and delayed the onset of sawteeth, compared to co FWCD. The partial absorption of fast waves by energetic beam ions at high harmonics of the ion cyclotron frequency was also evident from a build up of fast particle pressure near the magnetic axis and a correlated increase in the neutron rate. The anomalous fast particle pressure and neutron rate increased with increasing NBI power and peaked when a harmonic of the deuterium cyclotron frequency passed through the center of the plasma. The experimental FWCD efficiency was highest at 2 T where the interaction between the fast waves and the beam ions was weakest; as the magnetic field strength was lowered, the FWCD efficiency decreased to approximately half of the maximum theoretical value.

In modeling electron cyclotron (EC) waves for heating (ECH) and current drive (ECCD) applications, the standard approach describes wave propagation using geometric optic ray tracing with cold plasma dispersion and wave absorption using a relativistic warm plasma expression. However, recent vertical O-mode transmission measurements on Tore Supra indicate that wave trajectories near the fundamental resonance frequency can significantly deviate from predictions of cold plasma analysis. The experimental results were attributed to warm plasma refraction effects caused by the anomalous dispersion associated with wave-particle resonance. Here, warm plasma refraction effects on wave propagation and absorption are examined in the context of a slab model in the parameter regime of interest to the upcoming 110 GHz electron cyclotron heating and current drive experiments on DIII-D.

The application of fast wave power in DIII-D has proven effective for both electron heating and current drive. Since the last RIF Conference FW power has been applied to advanced confinement regimes in DIII-D; negative central shear (NCS), VH- and H-modes, high {beta}{sub p}, and high-{ell}i. Typically these regimes show enhanced confinement of toroidal momentum exhibited by increased toroidal rotation velocity. Indeed, layers of large shear in toroidal velocity are associated with transport barriers. A rather common occurrence in these experiments is that the toroidal rotation velocity is decreased when the FW power is turned on, to lowest order independent of whether the antennas are phased for co or counter current drive. At present all the data is for co-injected beams. The central toroidal rotation can be reduced to 1/2 of the non-FW level. Here the authors describe the effect in NCS discharges with co-beam injection.

To fully utilize the available power sources in DIII–D (FW, NBI, ECH), understanding of the synergism between the heating mechanisms is important. In this paper the ion distribution, under simultaneous application of NBI and FW, is calculated from Fokker‐Planck code CQL3D coupled to ray‐tracing code CURRAY. It is found that interaction between energetic ions and FW can be minimized or maximized by adjusting various parameters such as magnetic field, density, beam energy, and FW frequency. Specifically, in DIII–D, we find negligible interactions above 1.8 T and above 80 MHz, while the interaction increases at lower fields and frequencies. The results are compared with experiments in DIII–D including the calculated neutron rate. Energetic ion orbit losses may play an important role in the ion distribution, and this effect is being investigated.

The physics of electron heating and current drive with the fast magnetosonic wave has been demonstrated on DIII-D, in reasonable agreement with theoretical modeling. A recently completed upgrade to the fast wave capability should allow full noninductive current drive in steady state advanced confinement discharges and provide some current density profile control for the Advanced Tokamak Program. DIII-D now has three four-strap fast wave antennas and three transmitters, each with nominally 2 MW of generator power. Extensive experiments have been conducted with the first system, at 60 MHz, while the two newer systems have come into operation within the past year. The newer systems are configured for 60 to 120 MHz. The measured FWCD efficiency is found to increase linearly with electron temperature as {gamma} = 0.4 {times} 10{sup 18} T{sub eo} (keV) [A/m{sup 2}W], measured up to central electron temperature over 5 keV. A newly developed technique for determining the internal noninductive current density profile gives efficiencies in agreement with this scaling and profiles consistent with theoretical predictions. Full noninductive current drive at 170 kA was achieved in a discharge prepared by rampdown of the Ohmic current. Modulation of microwave reflectometry signals at the fast wave frequency is beingmore » used to investigate fast wave propagation and damping. Additionally, rf pick-up probes on the internal boundary of the vessel provide a comparison with ray tracing codes, with dear evidence for a toroidally directed wave with antenna phasing set for current drive. There is some experimental evidence for fast wave absorption by energetic beam ions at high cyclotron harmonic resonances.« less

The effect of co and counter fast wave current drive (FWCD) on the plasma current profile has been measured for neutral beam heated plasmas with reversed magnetic shear on the DIII‐D tokamak. Although the response of the loop voltage profile was consistent with the application of co and counter FWCD, little difference was observed between the current profiles for the opposite directions of FWCD. The evolution of the current profile was successfully modeled using the ONETWO transport code. The simulation showed that the small difference between the current profiles for co and counter FWCD was mainly due to an offsetting change in the ohmic current profile. In addition, the time scale for the loop voltage to reach equilibrium (i.e., flatten) was found to be much longer than the FWCD pulse, which limited the ability of the current profile to fully respond to co or counter FWCD.

A combined moment and kinetic approach is developed to consider rf effects on plasma rotation. Appropriate relaxation times for driven toroidal and poloidal rotation are discussed.

Current drive during second harmonic, electron cyclotron heating experiments performed on the T‐10 tokamak have been simulated with the onetwo transport code to determine the effects of induction on the time evolution of the loop voltage and current density profile. Ray tracing shows the well focused rf power can generate centrally peaked current densities which exceed the Ohmic current densities by a factor of five, causing very peaked current profiles which will be unstable to sawteeth. A Kadomtsev model of the sawtooth shows that a limit cycle is quickly reached which maintains a broad current profile and requires generation of a negative dc component of the loop voltage localized near the magnetic axis. This negative electric field effectively reduces the measured current drive efficiency. A broader profile of driven current, as in the fundamental current drive experiment on T‐10, would not suffer this effect.

The CQL3D Fokker‐Planck code is used to investigate effects of quasilinear distortion of the electron tail in the T–10 second harmonic electron cyclotron current (ECCD) drive experiment. The experiment operates in a regime of substantial tail formation. Current drive efficiency may be doubled relative to low power cases. That portion of electric field‐driven current which is synergetic with the rf‐induced nonthermal tail may tend to cancel the ECCD current in relevant cases.

Current drive by fast waves (FWCD) is an important candidate for steady‐state operation of tokamaks. Major experiments using this scheme are being carried out on DIII‐D. There has been considerable study of the theoretical efficiency of FWCD. In Refs. 4 and 5, the nonrelativistic efficiency of FWCD at arbitrary frequencies was studied. For DIII‐D parameters, the results can be considerably different from the Landau and Alfven limits. At the high temperatures of reactors and DIII‐D upgrade, relativistic effects become important. In this paper, the relativistic FWCD efficiency for arbitrary frequencies is studied. Assuming that the plasma is weakly relativistic, i.e., Te/mc2 is small, an analytic expression for FWCD is obtained for high resonant energies (uph/uTe≫1). Comparisons with the results from a numerical code ADJ and the nonrelativistic results shall be made and analytical fits in the whole range of velocities shall be presented.