CP Asymmetries in B to f_0 K_S Decays

We consider the branching ratio and the CP asymmetries in B to f_0(980)K_S decay to the end of determining the deviation of the time-dependent CP asymmetry from sin(2 beta) arising from Standard Model physics. We obtain Delta S_{f_0 K_S} within the context of the QCD factorization framework for the B to f_0(980)K_S decay amplitudes assuming the f_0(980) is a q\bar{q} state and employing a random scan over the theoretical parameter space to assess the possible range in Delta S_{f_0 K_S}. Imposing the value of the experimental branching ratio within 1 sigma and 3 sigma, respectively, of its central value as a constraint, we find the range of Delta S_{f_0 K_S} to be [0.018, 0.033] for a scan in which the parameters are allowed to vary within 1 sigma of their central values and the range [-0.019, 0.064] for a scan in which the parameters vary within 3 sigma of their central values.Comment: 27 pages, 10 figures, references adde

Studies of structural, magnetic, electrical and photoconducting properties of Bi1−x_{1-x}Cax_{x}MnO3_{3} epitaxial thin films

The dynamics of the charge ordered (CO) state under non-equilibrium conditions created by strong dc-electric field (~106 V/cm) and photo-illumination with short (~ 6 ns) laser pulses is investigated in Bi1-xCaxMnO3 (x > 0.5) epitaxial films. A pulsed laser deposition method was used to synthesize films on (100) LaAlO3 (LAO) and (100) SrTiO3 (STO) substrates. The crystallographic structure, temperature dependence of electrical resistivity and magnetization of the samples of different composition prepared under different oxygen partial pressure (pO2) and deposition temperature (TD) are studied. For the x = 0.6 sample grown on LAO, a clear signature of charge ordering at ~275 K is seen in the magnetization and at ~ 260 K in the resistivity data. The same sample grown on STO revealed a complex behavior, which entails charge ordering at ~300 K, a Neel order at ~150 K and finally a weak ferromagnetic phase below 50 K. A strong correlation between charge ordering temperature (TCO) and the c-axis lattice parameter (c) of the type (dTCO/dc ~-350 K/A) imerges from measurements on films deposited under different growth conditions. Since the out of plane lattice parameter (c) increases with in plane compressive strain, this effect directly show a compressive strain induced suppression of the TCO. The current (I)- voltage (V) characteristics of the samples at T < TCO show hysteresis due to a compound effect of Joule heating and collapse of the CO state. Transient changes in conductivity of lifetime ranging from nano to microseconds are seen at T < TCO on illumination with pulsed UV (355 nm) radiation. These observations are explained on the basis of the topological and electronic changes in the charge ordered phase.Comment: 19 figures, 34 page

ScanComplete: Large-Scale Scene Completion and Semantic Segmentation for 3D Scans

We introduce ScanComplete, a novel data-driven approach for taking an incomplete 3D scan of a scene as input and predicting a complete 3D model along with per-voxel semantic labels. The key contribution of our method is its ability to handle large scenes with varying spatial extent, managing the cubic growth in data size as scene size increases. To this end, we devise a fully-convolutional generative 3D CNN model whose filter kernels are invariant to the overall scene size. The model can be trained on scene subvolumes but deployed on arbitrarily large scenes at test time. In addition, we propose a coarse-to-fine inference strategy in order to produce high-resolution output while also leveraging large input context sizes. In an extensive series of experiments, we carefully evaluate different model design choices, considering both deterministic and probabilistic models for completion and semantic inference. Our results show that we outperform other methods not only in the size of the environments handled and processing efficiency, but also with regard to completion quality and semantic segmentation performance by a significant margin.Comment: Video: https://youtu.be/5s5s8iH0NF

Thermal Modeling of Metal Powder-Based Selective Laser Sintering

In order to get a better understanding of Selective Laser Sintering (SLS) process of the metal powders, three-dimensional modeling of laser sintering of a metal powder mixture that contains two kinds of metal powder with significantly different melting points under a moving Gaussian laser beam is investigated numerically. Laser induced melting and resolidification accompanied by shrinkage are modeled using a temperature transforming model. The liquid flow of the melted low melting point metal driven by capillary and gravity forces is also included in the physical model. Both complete and partial shrinkages are considered in the model. Simulations are performed for both single line laser scanning and multiple-line laser scanning. The numerical results are compared with experimental results and a detailed parametric study is performed. The effects of the moving heat source intensity, the scanning velocity, the thickness of the powder layer and the number of existing sintered layers underneath on the sintering depth, the shape of the heat affected zone (HAZ) and the temperature distribution are discussed. The optimized dimensionless moving heat source intensity increases with increasing scanning velocity in order to achieve the desired sintering depth and bond the newly sintered layer to the previously sintered layers.Mechanical Engineerin

Spiral Growth Manufacturing (SGM) – A Continuous Additive Manufacturing Technology for Processing Metal Powder by Selective Laser Melting

Spiral growth manufacturing is a new innovative powder based rapid manufacturing technique. The innovation exists in the methodology in which powder layers are deposited. Unlike other pre-placed powder systems, the deposited layers move relative to the location at which they are processed. This is made possible by a rotating build drum into which powder is deposited, in spiralled layers, from a stationary hopper. With this configuration powder can be continuously deposited and levelled and simultaneously processed, eliminating delays in the build cycle. Stainless steel and cobalt-chrome powder is selectively melted using a 100W flash lamp pumped Nd:YAG laser. This paper reports on factors affecting build rate and on build strategies for creating a number of axis-symmetric thin and thick walled cylinders. Experimental results suggest that build rate for thin walled structures bonded to a substrate will ultimately be governed by tangential movements of the powder particles when frictional forces are not sufficient to accelerate the particles along a curved path, provided that enough laser power is available for melting. Even melt pool balling, which is evident when melting one layer at high speeds, diminishes in multiple layer builds due to re-melting and infilling.Mechanical Engineerin

Quarkonium production in the LHC era: a polarized perspective

Polarization measurements are usually considered as the most difficult challenge for the QCD description of quarkonium production. In fact, global data fits for the determination of the non-perturbative parameters of bound-state formation traditionally exclude polarization observables and use them as a posteriori verifications of the predictions, with perplexing results. With a change of perspective, we move polarization data to the centre of the study, advocating that they actually provide the strongest fundamental indications about the production mechanisms, even before we explicitly consider perturbative calculations. Considering psi(2S) and Y(3S) measurements from LHC experiments and state-of-the-art NLO short-distance calculations in the framework of non-relativistic QCD factorization (NRQCD), we perform a search for a kinematic domain where the polarizations can be correctly reproduced together with the cross sections, by systematically scanning the phase space and accurately treating the experimental uncertainties. This strategy provides a straightforward solution to the "quarkonium polarization puzzle" and reassuring signs that the theoretical framework is reliable. At the same time, the results expose unexpected hierarchies in the non-perturbative NRQCD parameters, that open new paths towards the understanding of bound-state formation in QCD.Comment: Submitted to Phys. Lett.