Analysis of irradiation processes for laser-induced periodic surface structures

The influence of errors on the irradiation process for laser-induced periodic surface structures (LIPSS) was studied theoretically with energy density simulations. Therefore an irradiation model has been extended by a selection of technical variations. The influence of errors has been found in a deviation from optimal conditions, by a shift or spread of accumulated fluence and a variation of local fluence, related to variations of the peak fluence and relative pulse intersection. The analysis of the irradiation process by energy density simulations, gives the possibility to perform realistic irradiation simulations and derive optimization strategies for the determination of irradiation parameters. This analysis is required for the application of LIPSS for surface functionalization. © 2013 The Authors

Towards Friction Control using laser-induced periodic Surface Structures

This paper aims at contributing to the study of laser-induced periodic surface structures (LIPSS) and the description of their tribological properties in order to facilitate the knowledge for contact mechanical applications. To obtain laser parameters for LIPSS formation, we propose to execute two D2-Experiments. For the transfer of results from static experiments to areas of LIPSS we propose the discrete accumulation of fluences. Areas covered by homogeneously distributed LIPSS were machined. Friction force of these areas was measured using a tribometer in a ball on flat configuration. The friction force was found to be higher on the structured area than on the initial surface

Finite-difference Time-domain Modeling of Laser-induced Periodic Surface Structures

Laser-induced periodic surface structures (LIPSSs) consist of regular wavy surface structures with amplitudes the (sub)micrometer range and periodicities in the (sub)wavelength range. It is thought that periodically modulated absorbed laser energy is initiating the growth of LIPSSs. The “Sipe theory” (or “Efficacy factor theory”) provides an analytical model of the interaction of laser radiation with a rough surface of the material, predicting modulated absorption just below the surface of the material. To address some limitations of this model, the finite-difference time-domain (FDTD) method was employed to numerically solve the two coupled Maxwell's curl equations, for linear, isotropic, dispersive materials with no magnetic losses. It was found that the numerical model predicts the periodicity and orientation of various types of LIPSSs which might occur on the surface of the material sample. However, it should be noted that the numerical FDTD model predicts the signature or “fingerprints” of several types of LIPSSs, at different depths, based on the inhomogeneously absorbed laser energy at those depths. Whether these types of (combinations of) LIPSSs will actually form on a material will also depend on other physical phenomena, such as the excitation of the material, as well as thermal-mechanical phenomena, such as the state and transport of the materia

Greenhouse gas fluxes from arable land in the Netherlands : BSIK-KvR programme ME-1

Koolstofdioxide (CO2), methaan (CH4) en lachgas (N2O) zijn de belangrijkste broeikasgassen, die verantwoordelijk zijn voor de opwarming van de aarde (klimaatverandering). Het is van belang om broeikasgasemissies uit verschillende bronnen te kunnen kwantificeren. In dit rapport worden de resultaten gepresenteerd van N2O en CH4 emissiemetingen bij twee akkerbouw-locaties in Nederlan

Laser-induced periodic surface structures:Fingerprints of light localization

The finite-difference time-domain (FDTD) method is used to study the inhomogeneous absorption of linearly polarized laser radiation below a rough surface. The results are first analyzed in the frequency domain and compared to the efficacy factor theory of Sipe and coworkers. Both approaches show that the absorbed energy shows a periodic nature, not only in the direction orthogonal to the laser polarization, but also in the direction parallel to it. It is shown that the periodicity is not always close to the laser wavelength for the perpendicular direction. In the parallel direction, the periodicity is about lambda/Re((n) over tilde), with (n) over tilde being the complex refractive index of the medium. The space-domain FDTD results show a periodicity in the inhomogeneous energy absorption similar to the periodicity of the low-and high-spatial-frequency laser-induced periodic surface structures depending on the material's excitation

Theta Phase Entrainment of Single-Cell Spiking in Rat Somatosensory Barrel Cortex and Secondary Visual Cortex Is Enhanced during Multisensory Discrimination Behavior

Phase entrainment of cells by theta oscillations is thought to globally coordinate the activity of cell assemblies across different structures, such as the hippocampus and neocortex. This coordination is likely required for optimal processing of sensory input during recognition and decision-making processes. In quadruple-area ensemble recordings from male rats engaged in a multisensory discrimination task, we investigated phase entrainment of cells by theta oscillations in areas along the corticohippocampal hierarchy: somatosensory barrel cortex (S1BF), secondary visual cortex (V2L), perirhinal cortex (PER), and dorsal hippocampus (dHC). Rats discriminated between two 3D objects presented in tactile-only, visual-only, or both tactile and visual modalities. During task engagement, S1BF, V2L, PER, and dHC LFP signals showed coherent theta-band activity. We found phase entrainment of single-cell spiking activity to locally recorded as well as hippocampal theta activity in S1BF, V2L, PER, and dHC. While phase entrainment of hippocampal spikes to local theta oscillations occurred during sustained epochs of task trials and was nonselective for behavior and modality, somatosensory and visual cortical cells were only phase entrained during stimulus presentation, mainly in their preferred modality (S1BF, tactile; V2L, visual), with subsets of cells selectively phase-entrained during cross-modal stimulus presentation (S1BF: visual; V2L: tactile). This effect could not be explained by modulations of firing rate or theta amplitude. Thus, hippocampal cells are phase entrained during prolonged epochs, while sensory and perirhinal neurons are selectively entrained during sensory stimulus presentation, providing a brief time window for coordination of activity

Rendementsmeting luchtwasser 90/95% ammoniakreductie Inno- en luchtwassysteem

Om de emissies van ammoniak te reduceren is invoering van emissiebeperkende staltechnieken noodzakelijk. Luchtwassystemen behoren tot de systemen die in de Regeling ammoniak en veehouderij (Rav) opgenomen zijn als ammoniakemissiereducerende technieken. Het principe van een chemische wasser is erop gebaseerd dat NH3 die zich in de stallucht bevindt wordt gebonden door het aanwezige zuur in de wasser. Inno+ BV brengt een nieuw type chemische wasser dat gebaseerd is op het in serie plaatsen van twee wascomponenten die ieder 70% ammoniak reduceren. Het verwachte reductiepercentage van dit systeem is 95% en moet worden gemeten voordat men het kan opnemen in de Rav. Inno+ BV heeft de Animal Science Group opdracht gegeven om het rendement van het 90-95% ammoniakreductie Inno+ Luchtwassysteem vast te stellen. Deze metingen worden volgens het nieuwe meetprotocol voor ammoniak uitgevoerd. In dit project werd het wanden concept bij twee pluimveestallen (vleeskuikenouderdieren en vleeskuikens) en het module concept bij twee varkensstallen (stal met biggen, kraam- en dragende zeugen en een stal met biggen en kraamzeugen) gemeten. De ammoniakconcentratie werd volgens de natchemische meetmethode voor NH3 bepaald. In totaal werden 16 metingen uitgevoerd waarbij bij iedere meting de NH3-concentratie in de ingaande en uitgaande lucht in duplo werd gemeten. De variatie in NH3-concentratie van de ingaande lucht groot was groot (0,4 tot 84 ppm). De variatie van de uitgaande lucht was echter beperkt (0,03 tot 0,39 ppm). Het rendement van de chemische wasser varieerde van 84,2 tot 99,9%. Gemiddeld was het rendement 96,9% (96,4% inclusief meting 4 op locatie 1: bij deze meting was de zuurvoorraad aan het einde van de meting op

Maatregelen ter vermindering van fijnstofemissie uit de pluimveehouderij: validatie van een ionisatiesysteem op vleeskuikenbedrijven = Measures to reduce fine dust emission from poultry: validation of an ionization system on broiler farms

In this study, the fine dust emission reduction of a negative ionization system was determined through validation measurements on broiler farms