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A Feynman-Kac-type formula for the deterministic and stochastic wave equations and other P.D.E.'s
No full textPRO
Thermal-hydraulic analysis of alternative cable-in-conduit conductors for the European DEMO hybrid central solenoid
No full textA hybrid design of the Central Solenoid is under study within the conceptual design phase of the European DEMO fusion reactor. It is based on HTS conductors in the innermost high-field layers, and Nb3Sn and NbTi conductors for field values below 15 T. Since the resistance of the stainless steel jacket to mechanical fatigue drives the whole magnet design, alternative layouts of the cable-in-conduit conductors are aimed at decoupling the mechanical and hydraulic functions of the jacket itself. Thus, a reduced steel thickness, a smaller radial build of the coil and a larger magnetic flux are achievable. In this work, we analyse a new cable design based on filled conductors and tight He channels, both for the HTS and the LTS layers, and study their thermal-hydraulic performance by means of numerical simulations. After having introduced the geometrical and material details of the considered conductors, we describe the model and assumptions made for estimating the AC losses, assumed as the only heating source. Finally, we discuss the resulting minimum temperature margin of the conductors and provide useful insights for future activities on conductor development.SP
Preface
No full textLCSBFIELD Section Title:Chemical Engineering Department,Pennsylvania State University,University Park,PA,USA. FIELD URL:written in English
3D Printing of Double Network Granular Elastomers with Locally Varying Mechanical Properties
No full textFast advances in the design of soft actuators and robots demand for new soft materials whose mechanical properties can be changed over short length scales. Elastomers can be formulated as highly stretchable or rather stiff materials and hence, are attractive for these applications. They are most frequently cast such that their composition cannot be changed over short length scales. A method that allows to locally change the composition of elastomers on hundreds of micrometer lengths scales is direct ink writing (DIW). Unfortunately, in the absence of rheomodifiers, most elastomer precursors cannot be printed through DIW. Here, 3D printable double network granular elastomers (DNGEs) whose ultimate tensile strain and stiffness can be varied over an unprecedented range are introduced. The 3D printability of these materials is leveraged to produce an elastomer finger containing rigid bones that are surrounded by a soft skin. Similarly, the rheological properties of the microparticle-based precursors are leveraged to cast elastomer slabs with locally varying stiffnesses that deform and twist in a predefined fashion. These DNGEs are foreseen to open up new avenues in the design of the next generation of smart wearables, strain sensors, prosthesis, soft actuators, and robots.|A novel ink composed of jammed precursor-loaded elastomeric microparticles that can be direct ink written into double network granular elastomers that can attain a wide range of stiffnesses and ultimate tensile strains is presented. Inks with different stiffnesses can be 3D printed into cm-sized structures with locally varying compositions and hence mechanical properties using commercial multinozzle 3D printers. imageSMA
Doping of Alkali, Alkaline-Earth, and Transition Metals in Covalent-Organic Frameworks for Enhancing CO2 Capture by First-Principles Calculations and Molecular Simulations
No full textWe use the multiscale simulation approach, which combines the first-principles calculations and grand canonical Monte Carlo simulations, to comprehensively study the doping of a series of alkali (Li, Na, and K), alkaline-earth (Be, Mg, and Ca), and transition (Sc and Ti) metals in nanoporous covalent organic frameworks (COFs), and the effects of the doped metals on CO2 capture. The results indicate that, among all the metals studied, Li, Sc, and Ti can bind with COFs stably, while Be, Mg, and Ca cannot, because the binding of Be, Mg, and Ca with COFs is very weak. Furthermore, Li, Sc, and Ti can improve the uptakes of CO2 in COFs significantly. However, the binding energy of a CO2 molecule with Sc and Ti exceeds the lower limit of chemisorptions and, thus, suffers from the difficulty of desorption. By the comparative studies above, it is found that Li is the best surface modifier of COFs for CO2 capture among all the metals studied. Therefore, we further investigate the uptakes of CO2 in the Li-doped COFs. Our simulation results show that at 298 K and 1 bar, the excess CO2 uptakes of the Li-doped COF-102 and COF-105 reach 409 and 344 mg/g, which are about eight and four times those in the nondoped ones, respectively. As the pressure increases to 40 bar, the CO2 uptakes of the Li-doped COF-102 and COF-105 reach 1349 and 2266 mg/g at 298 K, respectively, which are among the reported highest scores to date. In summary, doping of metals in porous COFs provides an efficient approach for enhancing CO2 capture. © 2010 American Chemical Society.LSMOLan, Jianhui Cao, Dapeng Wang, Wenchuan Smit, Beren
Generic 3D ball animation model for networked interactive VR environments
No full textThe paper describes a versatile, robust, and parametric ball animation model that can be used in many types of interactive virtual reality (VR) environments. The generic model is particularly useful for animation of ball-like objects such as tennis balls and footballs in networked collaborative environments where low frame rates, network delays and information losses complicate collision detection of fast moving objects. The ball animation model includes a multi-level physical modeling as well as collision detection and treatment. Finally, the parameterization of typical applications is discussedVRLABInst. fur Inf., Zurich Univ., Switzerlan
Belief control strategies for interactions over weak graphs
No full textIn diffusion social learning over weakly-connected graphs, it has been shown that influential agents end up shaping the beliefs of non-influential agents. In this paper, we analyse this control mechanism more closely and reveal some critical properties. In particular, we characterize the set of beliefs that can be imposed on non-influential agents (i.e., the set of attainable beliefs) and how the graph topology of these latter agents helps resist manipulation but only to a certain degree. We also derive a design procedure that allows influential agents to drive the beliefs of non-influential agents to desirable attainable states. We illustrate the results with two examples.AS
Ion scattering simulations of the Si(100)-SiO2 interface
No full textWe carry out ion scattering simulations to investigate the nature of the transition region at the Si(100)-SiO2 interface. Ion scattering experiments performed in the channeling geometry provide us with a genuine interfacial property, the excess Si yield, resulting from distortions in the Si substrate and from Si atoms in intermediate oxidation states. To interpret the ion scattering data, we first generate a series of model structures for the interface by applying sequentially classical molecular dynamics and density-functional relaxation methods. These models reproduce atomic-scale features consistent with a variety of available experimental data. Then, we design a classical scheme to perform ion scattering simulations on these model interfaces. In our study, we separate the excess Si yield obtained from experiments in two distinct contributions. First, Si atoms in intermediate oxidation states account for similar to 25% of the excess Si yield, a contribution that is fully determined by the population of suboxide determined from photoemission data. The remaining similar to 75% of the excess Si yield characterizes the amount of lateral distortion of the substrate Si layers in the vicinity of the Si(100)-SiO2 interface. The comparison between calculated and experimental excess Si yields indicates that the distortions propagating from the interface into the Si substrate are consistent with interfacial transition structures extending over more than two Si layers, eventually including a disordered bonding pattern. Nearly abrupt interfaces induce distortions in the upper layers of the Si substrate which are insufficient for reproducing the experimental excess Si yields.CSE