Results 1 - 10 of 1560
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[en] The present work attempts to formulate the equilibrium of axisymmetric plasma with purely toroidal flow within ideal MHD theory. In general, the inertial term Rho(v.Del)v caused by plasma flow is so complicated that the equilibrium equation is completely different from the Grad-Shafranov equation. However, in the case of purely toroidal flow the equilibrium equation can be simplified so that it resembles the Grad-Shafranov equation. Generally one arbitrary two-variable functions and two arbitrary single variable functions, instead of only four single-variable functions, are allowed in the new equilibrium equations. Also, the boundary conditions of the rotating (with purely toroidal fluid flow, static - without any fluid flow) equilibrium are the same as those of the static equilibrium. So numerically one can calculate the rotating equilibrium as a static equilibrium. (author)
[en] Modification of inorganic electrode surfaces has attracted great attention in the quest to optimize organic optoelectronic devices. An air-stable, cross-linkable trimethoxysilane functionalized hole-transporting triarylamine (4,4'-bis[(p-trimethoxysilylpropylphenyl)phenylamino]biphenyl, TPD-[Si(OMe)3]2) has been synthesized and self-assembled or spin-coated onto tin-doped indium oxide (ITO) anode surfaces to form monolayers or multilayer siloxane films, respectively. The modified ITO surfaces were characterized by advancing aqueous contact angle, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and cyclic voltammetry (CV). Increased surface work function and enhanced ITO-hole transport layer (HTL) contact via robust covalent bonding are expected to facilitate hole injection from the ITO anode, resulting in organic light-emitting diode (OLED) performance enhancement versus that of a device without such interlayers. For a device having the structure ITO/spin-coated-TPD-[Si(OMe)3]2 from aqueous alcohol + acetic acid blend solution (40 nm)/NPB (20 nm)/Alq (60 nm)/LiF (1 nm)/Al (100 nm), a maximum light output of 32800 cd/m2, a 4.25 V turn-on voltage, and a maximum current efficiency of 5.8 cd/A is achieved. This performance is comparable to or superior to that of analogous devices prepared with analogous trichorosilyl precursors. The air-stable interlayer material developed here is also applicable to large-area coating techniques.
[en] The Canadian Super-Critical Water-cooled Reactor (SCWR) is a Generation IV reactor that is being designed as part of the international initiative to design next generation nuclear reactors known as the Generation-IV International Forum (GIF). It is a heavy-water moderated pressure-tube type reactor that uses supercritical water as coolant (which allows ∼40% higher thermodynamic efficiency than current light-water reactors), employs passive safety systems, uses an insulated fuel channel design, and burns thorium as fuel for sustainability and proliferation resistance. The pressure tube design feature provides more flexibility to optimize the reactor efficiency in addition to enhancing reactor safety in comparison with other reactor designs. The operating pressure (25 MPa) and temperatures (typically 450oC to 625oC) of SCW reactors are significantly higher than those in existing light-water reactors, presenting design challenges that require innovative solutions. This paper provides a summary of current status of the mechanical design of the Canadian SCWR, discusses some of the design challenges and proposes path forward for future R&D to deal with these challenges. Also the paper discusses a variety of technologies that may be employed to achieve optimized reactor efficiency and increased plant reliability as well as plant economics. (author)
[en] The well-known theory of relaxed plasmas (Taylor states) is extended to external magnetic fields whose field lines intersect the conducting toroidal boundary. Application to an axially symmetric, large-aspect-ratio torus with circular cross section shows that the maximum pinch ratio, and hence the phenomenon of current saturation, is independent of the external field. The relaxed state is explicitly given for an external octupole field. In this case, field reversal is inhibited near parts of the boundary if the octupole generates magnetic x-points within the plasma. (orig.)
[en] The syntheses of the sandwich complexes ferrocene, (η5-C5H5)2-Fe, in 1951 and uranocene, (η8-C8H8)2U, in 1968 ushered in the modern eras of organotransition metal and organoactinide chemistry, respectively. Ferrocene and uranocene are examples of linear sandwich complexes, that is, those in which the (ring centroid)-M-(ring centroid) angle (denoted θ) is 180 degree. In the case of (η5-C5H5)2M chemistry, a number of bent (θ < 180degree) complexes are known when M is a main-group or rare-earth element. The explanation for the bent structures of these complexes has been the subject of some debate concerning the relative importance of covalent, electrostatic, and steric interactions. The authors report optimized geometries of Bz2An (An = Th-Am) and (η6-C6H3R3)2An (An = Th, U, Pu; R = Me, tBu) obtained by using local density approximation (LDA) and Perdew-Wang (PW91) gradient-corrected relativistic density functional theory (DFT) methods. These DFT methods are found to be able to reproduce the experimental geometries and vibrational frequencies of organoactinide complexes with satisfactory accuracy. The (TTB)2An calculations that are reported here are, to date, the largest full geometry optimizations to be carried out on an actinide system
[en] This paper describes the behavior of a plasma in a bar-mirror--combination magnetic well. The plasma is produced by collisional ionization of an electron beam, injected along the mirror axis, with neutral hydrogen molecules. Experimental results on such a plasma are also presented
[en] Here, negative compressibility ITG turbulence in a linear plasma device (CSDX) can induce a negative viscosity increment. However, even with this negative increment, we show that the total axial viscosity remains positive definite, i.e. no intrinsic axial flow can be generated by pure ITG turbulence in a straight magnetic field. This differs from the case of electron drift wave (EDW) turbulence, where the total viscosity can turn negative, at least transiently. When the flow gradient is steepened by any drive mechanism, so that the parallel shear flow instability (PSFI) exceeds the ITG drive, the flow profile saturates at a level close to the value above which PSFI becomes dominant. This saturated flow gradient exceeds the PSFI linear threshold, and grows with ∇T_i_0 as |∇V_∥|/|k_∥c_s|∼|∇T_i_0|"2"/"3/(k_∥T_i_0)"2"/"3. This scaling trend characterizes the effective stiffness of the parallel flow gradient.
[en] A semi-analytical simulation method is proposed in this paper to assess system reliability of structures. Monte Carlo simulation with variance-reduction techniques, systematic and antithetic sampling, is employed to obtain the samples of the structural resistance in this method. Variance-reduction techniques make it possible to sufficiently simulate the structural resistance with less runs of structural analysis. When resistance samples and its moments determined, exponential polynomial method (EPM) is used to fit the probability density function of the structural resistance. EPM can provide the approximate distribution and statistical characteristic of the structural resistance and then the first-order second-moment method can be carried out to calculate the structural failure probability. Numerical examples are provided for a structural component and two ductile frames, which illustrate the method proposed facilitates the evaluation of system reliability in assessments of structural safety
[en] This paper presents the weight functions for the determination of the stress intensity factor and T-stress solutions for edge-cracked plates with built-in ends under complex stress distributions. First, a compliance analysis approach is used to calculate stress intensity factor and T-stress for edge cracks in finite width plates with built-in ends with uniform or linear stress distributions acting on the crack face. The results serve as the reference solutions for the next step in which the approaches of deriving weight functions from reference stress intensity factor and T-stress solutions developed for stress boundary conditions are extended to obtain the corresponding weight functions for edge-cracked plates with built-in ends. Finite element analysis is conducted to validate the derived solutions. The weight functions derived are suitable for obtaining stress intensity factors and T-stress solutions under any complex stress field