Discriminability of tryptophan containing dipeptides using quantum control

We show that the coherent manipulation of molecular wavepackets in the excited states of trp-containing dipeptides allows efficient discrimination among them. Optimal dynamic discrimination fails, however, for some dipeptide couples. When considering the limited spectral resources at play (3nm bandwidth at 266nm), we discuss the concept of discriminability, which appears uncorrelated to both static spectra and relaxation lifetime

On the geometry of coating layers formed by overlap

A recursive model is presented for the prediction of the profile of a coating layer formed by single track overlap. A known shape of single track is assumed and on the base of simple physical assumptions the recursive sequence is deduced to construct an entire profile of such coatings. Calculations of these profiles for different basic shapes and overlaps of tracks show the dependence of coating thickness, waviness and cladding angle on these parameters. A generalized formulation of the model based on purely geometric considerations allows for an application towards different types of cladding processes, including multilayer cladding and 3D depositions. The model is tested experimentally for the laser cladding process in two different set-ups. The cladding track is formed by a continuous deposition of metallic particles into the melt-pool formed by a high power laser beam that continuously moves over a substrate. Good agreement with the parabolic shape of a single track and experimental observations of height and waviness was concluded for a wide range of overlap ratios.

Thickness and waviness of surface coatings formed by overlap:Modelling and experiment

Several surface engineering techniques are known that form a hard facing coating on an inexpensive substrate by a successive overlap of individual cladding tracks. Typical examples include laser cladding and laser additive manufacturing. Realistic predicting the final thickness and waviness of the coating as a function of geometry of single cladding track and their overlap are lacking in literature. In this contribution a recursive model for the calculation of the coating profile is presented. A few basic shapes of single tracks are presumed and on the basis of physical assumptions a recursive formula is deduced to construct a shape of the whole coating profile. Calculations of such profiles for different shapes of tracks and different overlaps show a dependence of the coating thickness and its waviness on these parameters. The model is tested experimentally for a laser cladding process, in which the laser track is formed by a continuous deposition of small metallic particles into the meltpool formed by a high power laser beam continuously moving over the substrate. © 2013 WIT Press

Prediction of coating geometry: theory and experiment

In this contribution we present a comparison between laser clad experiments and model predictions of the entire geometry of laser deposited multi-layered coatings. Recently we have shown that the recursive model describing the geometry of laser clad coatings combined with experimental track characteristics leads to specific functions describing the geometry of coatings formed by overlap of individual tracks depending on the processing parameters. The recursive model provides an adequate description of the whole geometry of the coating from the Height H and width w of a single laser track for any overlap ratio OR. We have shown that the height and width of a single track are well correlated with the main laser cladding processing parameters for both coaxial and side cladding set-ups. Combining these two approaches leads to a prediction of the complete geometry of laser clad coatings from a number of basic processing parameters. These parameters are: Feeding rate F, Laser beam scanning speed S and overlap ratio OR. The functions that describe the height and waviness of the final coating are the same for both coaxial and side cladding set-ups. These model predictions lead to very simple, yet very accurate predictions of the entire geometry of the laser deposited layers

A versatile model for the prediction of complex geometry in 3D direct laser deposition

We present a versatile model for the prediction of the geometry of laser clad depositions formed by overlap of individual tracks and layers as a 2D cross-sectional model that can be used for prediction of 3D structures. The main strength of our approach lies in the ability to achieve physically sound predictions of the geometry of deposition based entirely on experimental parameters that can be easily adjusted during the deposition process. As far as applications are concerned, with our model we are able to make predictions for any number of clad tracks and also any number of layers. We present two different ways of validating our model with experimental results, i.e. using a prediction based on the first track geometry and second, also a complete a priori prediction based on combined experimental dependencies in laser deposition process. The model therefore requires some level of prior experimental work to be conducted to calibrate the model for a particular set up which in turns makes the model very computationally simple and easy to apply. Good agreement with experiments in both scenarios is concluded

Optimal Dynamic Discrimination in Tryptophan-Containing Dipeptides

Optimal Dynamic Discrimination based on the phase-shaping of deep ultraviolet femtosecond pulses was applied to selectively modulate the time-resolved fluorescence depletion of pairs of tryptophan-containing dipeptides. Our results indicate that phase-sensitive excitation allows their differential identification, beyond the limits of linear and time-resolved spectroscopy

Texture development in direct powder deposition

A simple, versatile, and qualitative guide for the prediction interpretation of texture development in coatings and three dimensional objects formed by direct powder deposition is presented. The texture predictions are based on the direction of crystal growth during solidification based on both existing experimental evidence and theoretical understanding of the role of solid-liquid interface during solidification following laser melting of a material. The predictions are confirmed experimentally by electron back-scatter observations. (C) 2017 Laser Institute of America