Use of fused airborne scanning laser altimetry and digital map data for urban flood modelling

Flood modelling of urban areas is still at an early stage, partly because until recently topographic data of sufficiently high resolution and accuracy have been lacking in urban areas. However, Digital Surface Models (DSMs) generated from airborne scanning laser altimetry (LiDAR) having sub-metre spatial resolution have now become available, and these are able to represent the complexities of urban topography. The paper describes the development of a LiDAR post-processor for urban flood modelling based on the fusion of LiDAR and digital map data. The map data are used in conjunction with LiDAR data to identify different object types in urban areas, though pattern recognition techniques are also employed. Post-processing produces a Digital Terrain Model (DTM) for use as model bathymetry, and also a friction parameter map for use in estimating spatially-distributed friction coefficients. In vegetated areas, friction is estimated from LiDAR-derived vegetation height, and (unlike most vegetation removal software) the method copes with short vegetation less than ~1m high, which may occupy a substantial fraction of even an urban floodplain. The DTM and friction parameter map may also be used to help to generate an unstructured mesh of a vegetated urban floodplain for use by a 2D finite element model. The mesh is decomposed to reflect floodplain features having different frictional properties to their surroundings, including urban features such as buildings and roads as well as taller vegetation features such as trees and hedges. This allows a more accurate estimation of local friction. The method produces a substantial node density due to the small dimensions of many urban features.

Extraction of tidal channel networks from aerial photographs alone and combined with laser altimetry

Tidal channel networks play an important role in the intertidal zone, exerting substantial control over the hydrodynamics and sediment transport of the region and hence over the evolution of the salt marshes and tidal flats. The study of the morphodynamics of tidal channels is currently an active area of research, and a number of theories have been proposed which require for their validation measurement of channels over extensive areas. Remotely sensed data provide a suitable means for such channel mapping. The paper describes a technique that may be adapted to extract tidal channels from either aerial photographs or LiDAR data separately, or from both types of data used together in a fusion approach. Application of the technique to channel extraction from LiDAR data has been described previously. However, aerial photographs of intertidal zones are much more commonly available than LiDAR data, and most LiDAR flights now involve acquisition of multispectral images to complement the LiDAR data. In view of this, the paper investigates the use of multispectral data for semiautomatic identification of tidal channels, firstly from only aerial photographs or linescanner data, and secondly from fused linescanner and LiDAR data sets. A multi-level, knowledge-based approach is employed. The algorithm based on aerial photography can achieve a useful channel extraction, though may fail to detect some of the smaller channels, partly because the spectral response of parts of the non-channel areas may be similar to that of the channels. The algorithm for channel extraction from fused LiDAR and spectral data gives an increased accuracy, though only slightly higher than that obtained using LiDAR data alone. The results illustrate the difficulty of developing a fully automated method, and justify the semi-automatic approach adopted.

Effect of Er : YAG and diode laser irradiation on the root surface: Morphological and thermal analysis

Background: the aim of the present study was to compare the effects of Er:YAG and diode laser treatments of the root surface on intrapulpal temperature after scaling and root planing with hand instruments.Methods: Fifteen extracted single-rooted teeth were scaled and root planed with hand instruments. The teeth were divided into 3 groups of 5 each and irradiated on their buccal and lingual surfaces: group A: Er:YAG laser, 2.94 mum/100 mJ/10 Hz/ 30 seconds; group B: diode laser, 810 nm/1.0 W/0.05 ms/30 seconds; group C: diode laser, 810 nm/1.4 W/0.05 ms/30 seconds. The temperature was monitored by means of a type T thermocouple (copper-constantan) positioned in the pulp chamber to assess pulpal temperature during and before irradiation. Afterwards, the specimens were longitudinally sectioned, and the buccal and lingual surfaces of each root were analyzed by scanning electron microscopy.Results: In the Er:YAG laser group, the thermal analysis revealed an average temperature of -2.2 +/- 1.5degreesC, while in the diode laser groups, temperatures were 1.6 +/- 0.8degreesC at 1.0 W and 3.3 +/- 1.0degreesC at 1.4 W. Electronic micrographs revealed that there were no significant morphological changes, such as charring, melting, or fusion, in any group, although the specimens were found to be more irregular in the Er:YAG laser group.Conclusions: the application of Er:YAG and diode lasers at the utilized parameters did not induce high pulpal temperatures. Root surface irregularities were more pronounced after irradiation with an Er:YAG laser than with a diode laser.

In vitro study of the Nd : YAG laser effect on human dental enamel: Optical and scanning electron microscope analysis

Objective: the Nd:YAG laser irradiation of dental enamel was evaluated in enamel demineralization experiments in a Streptococcus mutans culture media. Summary Background Data: Previous studies had shown that a continuous wave Nd:YAG laser at an energy of approximately 67 mJ may induce an increased acid resistance in human dental enamel when exposed to severe demineralization conditions. Methods: Enamel windows of 3 x 4 cm in the buccal surface were irradiated with a continuous wave Nd:YAG laser at a wavelength of 1,064 Ecm using energy densities of from 83.75 to 187.50 J/cm(2), Enamel windows of 3 x 4 cm on the lingual surface served as control (without the laser irradiation). The enamel windows were then exposed to a Streptococcus mutans culture media at a temperature of 37 degrees C for 15 and 21 days. The laser effects and demineralization were examined both by optical microscopy and scanning electron microscopy (SEM), Results: A comparison between the lased and the unlased windows of enamel showed fusion and recrystalization of the enamel and increased acid-resistance in all groups irradiated with the Nd:YAG laser, on the other hand, the 3 x 4 delimited enamel surfaces from the control group (not irradiated with the Nd:YAG laser) showed 100% deminerization, Conclusions: These findings are consistent with the finding that laser irradiation of dental results in significant reduction of the effective solubility of enamel mineral.

Microestrutura e resistência à corrosão do Ti c.p. soldado a laser utilizando em prótese sobre implantes

Foram realizados estudos para avaliar a microestrutura, a dureza e a resistência à corrosão do titânio comercialmente puro-Ti c.p. soldado por laser e utilizado na confecção de prótese sobre implantes. Verificou-se que na soldagem a laser a microestrutura apresentou três regiões distintas: o cordão de solda, a zona afetada pelo calor - ZAC e o metal base. O Ti c.p. possui microestrutura granular, a microestrutura do cordão de solda é mais refinada e de maior dureza do que o metal base. A ZAC obtida por este processo de soldagem foi relativamente pequena quando comparada com o processo de soldagem por brasagem. Os ensaios eletroquímicos mostraram que a região da solda apresentou menor resistência à corrosão em meio de NaCl 0,15 molL-1 à temperatura ambiente.

Investigação da Interface Metal-Porcelana da Liga Ni-Cr-Mo Soldada a LASER

The interface formed between the metal and the porcelain of a LASER welded Ni-Cr-Mo alloy was studied. The characterization was carried out through optical microscopy, scanning electron microscopy, X-ray dispersive spectroscopy-EDS and mechanical testing by three-point flexion test-TPE in the region LASER welded with and without the porcelain. The porcelain adhesion with the alloy alone is possible after the oxidation of the metallic surface and subsequent application of an adhesive called opaco. The applied porcelain, on the base metal and fusion zone presented some distinct behaviors. After the TPF test the base metal presented fractures while that in the fusion zone was completely gone. One noticed that the region submitted to the LASER welding showed less porcelain adhesion than the region of the base metal due to the microestructural refinement of the fusion zone. These results can be evidenced by the EDS of the studied regions. The TPF had demonstrated that the Ni-Cr-Mo alloy submitted to the LASER welding, undergone significant alterations in its mechanical properties after the application of the porcelain.

Laser weld: microstructure and corrosion study of Ag-Pd-Au-Cu alloy of the dental application

The laser Welding process was introduced into dentistry by the end of the 1980s, resulting on a great impulse to that area with the development of cheaper and smaller equipment, using simpler technique. This allowed greater use of that process on the confection of prostheses compared to the brazing process since the heat source for that process is a concentrated light beam of high power, which minimizes distortion problems on the prosthetic pieces. Ag-Pd-Au-Cu alloy used on the confection of dental implant prostheses was observed before and after subjection to the laser welding process. The microstructure was analyzed with the. use of optic microscopy and the corrosion resistance was studied by the traditional electrochemical techniques and by electrochemical impedance, under environmental conditions simulating the aggressiveness found in the mouth cavity. A structural change was detected on the weld area, which presented a refined microstructure deriving from the high-speed cooling. The base metal out of the weld area presented a fusion coarse microstructure. The electrochemical essays showed differences on the potentiodynamic polarization behavior in both weld and metal base areas, indicating superior corrosion resistance in the weld area. The impedance spectra were characterized by capacitive distorted components, presenting linear impedance in the low frequencies area. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Morphological assessment of dentine and cementum following apicectomy with Zekrya burs and Er:YAG laser associated with direct and indirect Nd:YAG laser irradiation

Objectives. This study aimed to assess the apical surface morphology of maxillary central incisors resected 3.0 mm from the tooth apex using Zekrya burs or Er:YAG laser, with or without subsequent direct Nd:YAG laser irradiation (apical and buccal surfaces) and indirect irradiation (palatal surface).Study design. Forty maxillary central incisors were instrumented and obturated. The roots were divided into 4 groups according to the root resection method (Zekrya bur or Er: YAG laser -1.8 W, 450 mJ, 4 Hz, 113 J/cm(2)) and further surface treatment (none or Nd: YAG laser -2.0 W, 100 mJ, 20 Hz, 124 J/cm(2)). The teeth were prepared for SEM analysis. Scores ranging from 1 to 4 were attributed to cut quality and morphological changes. The data were analyzed by the Kruskal-Wallis test and by Dunn's test.Results. SEM images showed irregular surfaces on the apical portions resected with Zekrya burs, with smear layer and grooves in the resected dentine and slight gutta-percha displacement and plasticization. on the other hand, apicectomies carried out with Er: YAG laser showed morphological changes compatible with ablated dentine, with rough surfaces and craters. In spite of the presence of plasticized gutta-percha, with the presence of bubbles, an irregular adaptation of the filling material to the root walls was also observed. Direct Nd: YAG laser irradiation of the apical and buccal surfaces of the resected roots resulted in areas of resolidification and fusion in the dentine and cementum, with a vitrified aspect; indirect Nd: YAG laser irradiation of the palatal surfaces yielded a lower number of changes in the cementum, with irregular resolidification areas.Conclusions. There were no differences in terms of cut quality between the use of burs and Er: YAG laser or between the 2 surfaces (apical and buccal) treated with Nd: YAG laser with direct irradiation. However, morphological changes were significantly less frequent on surfaces submitted to indirect irradiation (palatal) when compared with those directly irradiated. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 109: e77-e82)

Nd:YAG Laser Irradiation effect on apical intracanal dentin-a microleakage and SEM evaluation

The purpose of this in vitro study was to evaluate the effect of neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation on intracanal dentin surface by SEM analysis and its interference in the apical seal of filled canals. After endodontic treatment procedures, 34 maxillary human incisors were randomly assigned to 2 groups. In the negative control group (n=17), no additional treatment was performed and teeth were filled with vertically condensed gutta-percha; in the laser-treated group (n=17), the root canals were irradiated with Nd:YAG laser (1.5 W, 100 mJ, 15 Hz) before filling as described for the control group. Two specimens of each group were prepared for SEM analysis to evaluate the presence and extent of morphological changes and removal of debris; the other specimens were immersed in 0.5% methylene blue dye (pH 7.2) for 24 h for evaluation of the linear dye leakage at the apical third. SEM analysis of the laser-treated group showed dentin fusion and resolidification without smear layer or debris. The Student's t-test showed that the laser-treated group had significantly less leakage in apical third than the control group. Within the limitations of this study, it may be concluded that the morphological changes on the apical intraradicular dentin surface caused by Nd:YAG laser resulted in less linear dye apical leakage.

Estudo do comportamento mecânico e microestrutural de um aço maraging após soldagem a laser e tratamentos térmicos

Pós-graduação em Engenharia Mecânica - FEG

Effects of laser beam energy on the pulsed Nd:YAG laser welding of thin sheet corrosion resistant materials

The aim of this study was to value the possibility to join, for pulsed Nd:YAG laser welding, thin foils lap joints for sealing components in corrosive environment. Experimental investigations were carried out using a pulsed neodymium: yttrium aluminum garnet laser weld to examine the influence of the pulse energy in the characteristics of the weld fillet. The pulse energy was varied from 1.0 to 2.5 J at increments of 0.25 J with a 4 ms pulse duration. The base materials used for this study were AISI 316L stainless steel and Ni-based alloys foils with 100 mu m thickness. The welds were analyzed by electronic and optical microscopy, tensile shear tests and micro hardness. The results indicate that pulse energy control is of considerable importance to thin foil weld quality because it can generate good mechanical properties and reduce discontinuities in weld joints. The ultimate tensile strength of the welded joints increased at first and then decreased as the pulse energy increased. In all the specimens, fracture occurred in the top foil heat-affected zone next to the fusion line. The microhardness was almost uniform across the parent metal, HAZ and weld metal. A slight increase in the fusion zone and heat-affected zone compared to those measured in the base metal was observed. This is related to the microstructural refinement in the fusion zone, induced by rapid cooling of the laser welding. The process appeared to be very sensitive to the gap between couples.

Determinação da resistência à flexão de ligas odontológicas, utilizadas em prótese parcial fixa e prótese sobre implante, soldadas por brasagem e a laser

Pós-graduação em Odontologia Restauradora - ICT

Heat Treatment and Yb-Fiber Laser Welding of a Maraging Steel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização mecânica e microestrutural de juntas soldadas a laser em aços maraging com posterior tratamento térmico e termoquímico de superfície a plasma

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Giunzione mediante laser di materiali difficili, ibridi ed a struttura cellulare

Lo studio presentato in questa sede concerne applicazioni di saldatura LASER caratterizzate da aspetti di non-convenzionalità ed è costituito da tre filoni principali. Nel primo ambito di intervento è stata valutata la possibilità di effettuare saldature per fusione, con LASER ad emissione continua, su pannelli Aluminum Foam Sandwich e su tubi riempiti in schiuma di alluminio. Lo studio ha messo in evidenza numerose linee operative riguardanti le problematiche relative alla saldatura delle pelli esterne dei componenti ed ha dimostrato la fattibilità relativa ad un approccio di giunzione LASER integrato (saldatura seguita da un post trattamento termico) per la realizzazione della giunzione completa di particolari tubolari riempiti in schiuma con ripristino della struttura cellulare all’interfaccia di giunzione. Il secondo ambito di intervento è caratterizzato dall’applicazione di una sorgente LASER di bassissima potenza, operante in regime ad impulsi corti, nella saldatura di acciaio ad elevato contenuto di carbonio. Lo studio ha messo in evidenza come questo tipo di sorgente, solitamente applicata per lavorazioni di ablazione e marcatura, possa essere applicata anche alla saldatura di spessori sub-millimetrici. In questa fase è stato messo in evidenza il ruolo dei parametri di lavoro sulla conformazione del giunto ed è stata definita l’area di fattibilità del processo. Lo studio è stato completato investigando la possibilità di applicare un trattamento LASER dopo saldatura per addolcire le eventuali zone indurite. In merito all’ultimo ambito di intervento l’attività di studio si è focalizzata sull’utilizzo di sorgenti ad elevata densità di potenza (60 MW/cm^2) nella saldatura a profonda penetrazione di acciai da costruzione. L’attività sperimentale e di analisi dei risultati è stata condotta mediante tecniche di Design of Experiment per la valutazione del ruolo preciso di tutti i parametri di processo e numerose considerazioni relative alla formazione di cricche a caldo sono state suggerite.