Partition functions of higher derivative conformal fields on conformally related spaces

The character integral representation of one loop partition functions is useful to establish the relation between partition functions of conformal fields on Weyl equivalent spaces. The Euclidean space Sa × AdSb can be mapped to Sa+b provided Sa and AdSb are of the same radius. As an example, to begin with, we show that the partition function in the character integral representation of conformally coupled free scalars and fermions are identical on Sa × AdSb and Sa+b. We then demonstrate that the partition function of higher derivative conformal scalars and fermions are also the same on hyperbolic cylinders and branched spheres. The partition function of the four-derivative conformal vector gauge field on the branched sphere in d = 6 dimension can be expressed as an integral over ‘naive’ bulk and ‘naive’ edge characters. However, the partition function of the conformal vector gauge field on $$ {S}_q^1 $$ S q 1 × AdS5 contains only the ‘naive’ bulk part of the partition function. This follows the same pattern which was observed for the partition of conformal p-form fields on hyperbolic cylinders. We use the partition function of higher derivative conformal fields on hyperbolic cylinders to obtain a linear relationship between the Hofman-Maldacena variables which enables us to show that these theories are non-unitary.

The Performance of 3D Printed Polymer Tools in Sheet Metal Forming

Additively manufactured polymer tools are evaluated for use in metal forming as prototype tools and in the attempt to make sheet metal more attractive to small production volumes. Printing materials, strategies and accuracies are presented before the tools and tested in V-bending and groove pressing of 1 mm aluminum sheets. The V-bending shows that the tools change surface topography during forming until a steady state is reached at around five strokes. The geometrical accuracy obtained in V-bending is evaluated by the spring-back angle and the resulting bend radius, while bending to 90° with three different punch nose radii. The spring-back shows additional effects from the elastic deflection of the tools, and the influence from the punch nose radius is found to be influenced by the printing strategy due to the ratio between tool radius and the printed solid shell thickness enclosing the otherwise less dense bulk part of the tool. Groove pressing shows the combined effect of groove heights and angular changes due to spring-back. In all cases, the repeatability is discussed to show the potential of tool corrections for obtaining formed parts closer to nominal values.

Design and Fabrication of CMOS Microstructures to Locally Synthesize Carbon Nanotubes for Gas Sensing

Carbon nanotubes (CNTs) can be grown locally on custom-designed CMOS microstructures to use them as a sensing material for manufacturing low-cost gas sensors, where CMOS readout circuits are directly integrated. Such a local CNT synthesis process using thermal chemical vapor deposition (CVD) requires temperatures near 900 °C, which is destructive for CMOS circuits. Therefore, it is necessary to ensure a high thermal gradient around the CNT growth structures to maintain CMOS-compatible temperature (below 300 °C) on the bulk part of the chip, where readout circuits are placed. This paper presents several promising designs of CNT growth microstructures and their thermomechanical analyses (by ANSYS Multiphysics software) to check the feasibility of local CNT synthesis in CMOS. Standard CMOS processes have several conductive interconnecting metal and polysilicon layers, both being suitable to serve as microheaters for local resistive heating to achieve the CNT growth temperature. Most of these microheaters need to be partially or fully suspended to produce the required thermal isolation for CMOS compatibility. Necessary CMOS post-processing steps to realize CNT growth structures are discussed. Layout designs of the microstructures, along with some of the microstructures fabricated in a standard AMS 350 nm CMOS process, are also presented in this paper.

Investigation of Carbon Fiber/Polyphenylenesulfone Composites by Method of X-Ray Photoelectron Spectroscopy

The surfaces of polyphenylenesulfone samples with the addition of carbon fibers were studied by X-ray photoelectron and Auger-electron spectroscopy. The state of carbon atoms on the surface, the electronic structure, and the distribution of carbon fibers in the surface region as a function of the concentration of the additive were studied. It is shown that with 10 mass. % carbon fiber addition, the transformation of peaks is mainly associated with an increase in the number of carboxyl groups in the matrix, while with a carbon content exceeding 10 mass. %, the increasing role of differential vertical charging becomes the dominant factor. A further increase in the carbon fiber concentration leads to an increase in the conductivity of the bulk part and, consequently, to a decrease in the charge layer without carbon fiber, and therefore, to a decrease in the broadening effect of the C 1s carbon peak.

Theoretical and numerical analysis of nano-actuators based on grafted polyelectrolytes in an electric field

We analyze, theoretically and by means of molecular dynamics (MD) simulations, the generation of mechanical force by a polyelectrolyte (PE) chain grafted to a plane and exposed to an external electric field; the free end of the chain is linked to a deformable target body. Varying the field, one can alter the length of the non-adsorbed (bulk) part of the chain and hence the deformation of the target body and the arising force. We focus on the impact of added salt on the magnitude of the generated force, which is especially important for applications. In particular, we develop a simple variational theory for the double layer formed near electrodes to compute the electric field acting on the bulk part of the chain. Our theoretical predictions agree well with the MD simulations. Next, we study the effectiveness of possible PE-based nano-vices, comprised of two clenching planes connected by PEs exposed to an external electric field. We analyze a novel phenomenon – two-dimensional diffusion of a nano-particle, clenched between two planes, and introduce a quantitative criterion for clenching efficiency, the clenching coefficient. It is defined as a logarithm of the ratio of the diffusion coefficients of a free and clenched particle. Using first a microscopic counterpart of the Coulomb friction model, and then a novel microscopic model based on surface phonons, with the vibration direction normal to the surface, we calculate the clenching coefficient as a function of the external electric field. Our results demonstrate a dramatic decrease of the diffusion coefficient of a clenched nano-particle for the range of parameters relevant for applications; this proves the effectiveness of the PE-based nano-vices.

Thermal Imaging of Laser Powder Deposition for Process Diagnostics

Thermal imaging is an important tool for future developments in Laser Powder Deposition (LPD). Thermal imaging of the LPD process is typically used for the verification of mathematical models describing the process and/or dynamic melt pool control. The research discussed here shows how thermal imaging can be used to improve our understanding of the connection between deposition parameters, thermal gradients, and final part quality. Data gathered from melt pool and bulk-part thermal images were used to correlate deposition parameters to final part quality. The results presented here are for applications in internal barrel cladding and laser brazing.

DIAGNOSTICS FOR GUIDED LASER PLASMA WAKEFIELD

The structure of the wakefield is studied in a gas filled capillary under conditions of a quasi-monomode laser pulse propagation in a capillary tube. Self-consistent numerical simulations show that in the central bulk part of a plasma where the laser intensity exceeds the ionization threshold, the wakefield structure is similar to that of an infinite homogeneous plasma. The efficient generation of a regular wakefield over long distances suitable for the laser wakefield accelerators is shown. The modification of the spectrum of a frequency doubled probe pulse traveling in a plasma wave created in the wake of a pump pulse guided inside a capillary tube is analyzed for the cases of narrow or broad chirped probe spectra. It is shown that in both cases the measurement of the spectrum can be used as a diagnostic for the amplitude of the plasma wave. The results of full scale numerical modeling confirm the developed analytical theory of wakefield diagnostics.

Study of the Mechanical Properties of Nanostructured Aluminum Obtained by SMAT

Enhanced mechanical properties were found on an Aluminum alloy treated by Surface Mechanical Attrition Treatment (SMAT) in this work. The average hardness of the annealed Aluminum alloy at the surface was enhanced up to 43% and reached 170 HV, and that of the bulk part could also be improved up to 20% which is 140 HV. The yield strength obtained under tensile test had significant improvement which may achieve up to 400 MPa. In this study, it is discovered that the surface nanostructured layer obtained by SMAT can be as thick as 100 μm and its effect can be observable along a specimen of 2 mm thickness. In the paper, more detailed experimental results will be presented as well as the experimental setup. The present study demonstrates the potential of the process for obtaining good strength on Aluminum alloy for aerospace applications.