Real-time error compensation of a three-axis machine tool using a laser tracker

The concept of measurement-enabled production is based on integrating metrology systems into production processes and generated significant interest in industry, due to its potential to increase process capability and accuracy, which in turn reduces production times and eliminates defective parts. One of the most promising methods of integrating metrology into production is the usage of external metrology systems to compensate machine tool errors in real time. The development and experimental performance evaluation of a low-cost, prototype three-axis machine tool that is laser tracker assisted are described in this paper. Real-time corrections of the machine tool's absolute volumetric error have been achieved. As a result, significant increases in static repeatability and accuracy have been demonstrated, allowing the low-cost three-axis machine tool to reliably reach static positioning accuracies below 35 μm throughout its working volume without any prior calibration or error mapping. This is a significant technical development that demonstrated the feasibility of the proposed methods and can have wide-scale industrial applications by enabling low-cost and structural integrity machine tools that could be deployed flexibly as end-effectors of robotic automation, to achieve positional accuracies that were the preserve of large, high-precision machine tools.

Experimental comparison of dynamic tracking performance of iGPS and laser tracker

External metrology systems are increasingly being integrated with traditional industrial articulated robots, especially in the aerospace industries, to improve their absolute accuracy for precision operations such as drilling, machining and jigless assembly. While currently most of the metrology assisted robotics control systems are limited in their position update rate, such that the robot has to be stopped in order to receive a metrology coordinate update, some recent efforts are addressed toward controlling robots using real-time metrology data. The indoor GPS is one of the metrology systems that may be used to provide real-time 6DOF data to a robot controller. Even if there is a noteworthy literature dealing with the evaluation of iGPS performance, there is, however, a lack of literature on how well the iGPS performs under dynamic conditions. This paper presents an experimental evaluation of the dynamic measurement performance of the iGPS, tracking the trajectories of an industrial robot. The same experiment is also repeated using a laser tracker. Besides the experiment results presented, this paper also proposes a novel method for dynamic repeatability comparisons of tracking instruments. © 2011 Springer-Verlag London Limited.

Liquid core fibre Bragg grating based refractive index sensor formed by femtosecond assisted chemical etching technique

We report the fabrication of a refractive index (RI) sensor based on a liquid core fibre Bragg grating (FBG). A micro-slot FBG was created in standard telecom optical fibre employing the tightly focused femtosecond laser inscription aided chemical etching. A micro-slot with dimensions of 5.74(h) × 125(w) × 1388.72(l) μm was engraved across the whole fibre and along 1mm long FBG which gives advantage of a relatively robust liquid core waveguide. The device performed the refractive index sensitivity up to about 742.72 nm/RIU. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Excimer laser surface ablation - a review

Corneal surface laser ablation procedures for the correction of refractive error have enjoyed a resurgence of interest, especially in patients with a possible increased risk of complications after lamellar surgery. Improvements in the understanding of corneal biomechanical changes, the modulation of wound healing, laser technology including ablation profiles and different methods for epithelial removal have widened the scope for surface ablation. This article discusses photorefractive keratectomy, trans-epithelial photorefractive keratectomy, laser-assisted sub-epithelial keratomileusis and epithelial-laser-assisted in situ keratomileusis. © 2010 The Authors. Journal compilation © 2010 Royal Australian and New Zealand College of Ophthalmologists.

Accuracy of computer-aided design/computer-assisted manufacture (CAD/CAM) fabricated dental restorations: a comparative study

Introduction: Computer-Aided-Design (CAD) and Computer-Aided-Manufacture (CAM) has been developed to fabricate fixed dental restorations accurately, faster and improve cost effectiveness of manufacture when compared to the conventional method. Two main methods exist in dental CAD/CAM technology: the subtractive and additive methods. While fitting accuracy of both methods has been explored, no study yet has compared the fabricated restoration (CAM output) to its CAD in terms of accuracy. The aim of this present study was to compare the output of various dental CAM routes to a sole initial CAD and establish the accuracy of fabrication. The internal fit of the various CAM routes were also investigated. The null hypotheses tested were: 1) no significant differences observed between the CAM output to the CAD and 2) no significant differences observed between the various CAM routes. Methods: An aluminium master model of a standard premolar preparation was scanned with a contact dental scanner (Incise, Renishaw, UK). A single CAD was created on the scanned master model (InciseCAD software, V2.5.0.140, UK). Twenty copings were then fabricated by sending the single CAD to a multitude of CAM routes. The copings were grouped (n=5) as: Laser sintered CoCrMo (LS), 5-axis milled CoCrMo (MCoCrMo), 3-axis milled zirconia (ZAx3) and 4-axis milled zirconia (ZAx4). All copings were micro-CT scanned (Phoenix X-Ray, Nanotom-S, Germany, power: 155kV, current: 60µA, 3600 projections) to produce 3-Dimensional (3D) models. A novel methodology was created to superimpose the micro-CT scans with the CAD (GOM Inspect software, V7.5SR2, Germany) to indicate inaccuracies in manufacturing. The accuracy in terms of coping volume was explored. The distances from the surfaces of the micro-CT 3D models to the surfaces of the CAD model (CAD Deviation) were investigated after creating surface colour deviation maps. Localised digital sections of the deviations (Occlusal, Axial and Cervical) and selected focussed areas were then quantitatively measured using software (GOM Inspect software, Germany). A novel methodology was also explored to digitally align (Rhino software, V5, USA) the micro-CT scans with the master model to investigate internal fit. Fifty digital cross sections of the aligned scans were created. Point-to-point distances were measured at 5 levels at each cross section. The five levels were: Vertical Marginal Fit (VF), Absolute Marginal Fit (AM), Axio-margin Fit (AMF), Axial Fit (AF) and Occlusal Fit (OF). Results: The results of the volume measurement were summarised as: VM-CoCrMo (62.8mm3 ) > VZax3 (59.4mm3 ) > VCAD (57mm3 ) > VZax4 (56.1mm3 ) > VLS (52.5mm3 ) and were all significantly different (p presented as areas with different colour. No significant differences were observed at the internal aspect of the cervical aspect between all groups of copings. Significant differences (p< M-CoCrMo Internal Occlusal, Internal Axial and External Axial 2 ZAx3 > ZAx4 External Occlusal, External Cervical 3 ZAx3 < ZAx4 Internal Occlusal 4 M-CoCrMo > ZAx4 Internal Occlusal and Internal Axial The mean values of AMF and AF were significantly (p M-CoCrMo and CAD > ZAx4. Only VF of M-CoCrMo was comparable with the CAD Internal Fit. All VF and AM values were within the clinically acceptable fit (120µm). Conclusion: The investigated CAM methods reproduced the CAD accurately at the internal cervical aspect of the copings. However, localised deviations at axial and occlusal aspects of the copings may suggest the need for modifications in these areas prior to fitting and veneering with porcelain. The CAM groups evaluated also showed different levels of Internal Fit thus rejecting the null hypotheses. The novel non-destructive methodologies for CAD/CAM accuracy and internal fit testing presented in this thesis may be a useful evaluation tool for similar applications.

Tailoring Magnetic, Mechanical and Dielectric Properties of Magnetorheological Elastomers based on Natural Rubber and Iron by Magnetic Field Assisted Curing for Possible Applications

If magnetism is universal in nature, magnetic materials are ubiquitous. A life without magnetism is unthinkable and a day without the influence of a magnetic material is unimaginable. They find innumerable applications in the form of many passive and active devices namely, compass, electric motor, generator, microphone, loud speaker, maglev train, magnetic resonance imaging, data recording and reading, hadron collider etc. The list is endless. Such is the influence of magnetism and magnetic materials in ones day to day life. With the advent of nanoscience and nanotechnology, along with the emergence of new areas/fields such as spintronics, multiferroics and magnetic refrigeration, the importance of magnetism is ever increasing and attracting the attention of researchers worldwide. The search for a fluid which exhibits magnetism has been on for quite some time. However nature has not bestowed us with a magnetic fluid and hence it has been the dream of many researchers to synthesize a magnetic fluid which is thought to revolutionize many applications based on magnetism. The discovery of a magnetic fluid by Jacob Rabinow in the year 1952 paved the way for a new branch of Physics/Engineering which later became magnetic fluids. This gave birth to a new class of material called magnetorheological materials. Magnetorheological materials are considered superior to electrorheological materials in that magnetorheology is a contactless operation and often inexpensive.Most of the studies in the past on magnetorheological materials were based on magnetic fluids. Recently the focus has been on the solid state analogue of magnetic fluids which are called Magnetorheological Elastomers (MREs). The very word magnetorheological elastomer implies that the rheological properties of these materials can be altered by the influence of an external applied magnetic field and this process is reversible. If the application of an external magnetic field modifies the viscosity of a magnetic fluid, the effect of external magnetic stimuli on a magnetorheological elastomer is in the modification of its stiffness. They are reversible too. Magnetorheological materials exhibit variable stiffness and find applications in adaptive structures of aerospace, automotive civil and electrical engineering applications. The major advantage of MRE is that the particles are not able to settle with time and hence there is no need of a vessel to hold it. The possibility of hazardous waste leakage is no more with a solid MRE. Moreover, the particles in a solid MRE will not affect the performance and durability of the equipment. Usually MR solids work only in the pre yield region while MR fluids, typically work in the post yield state. The application of an external magnetic field modifies the stiffness constant, shear modulus and loss modulus which are complex quantities. In viscoelastic materials a part of the input energy is stored and released during each cycle and a part is dissipated as heat. The storage modulus G′ represents the capacity of the material to store energy of deformation, which contribute to material stiffness. The loss modulusG′′ represents the ability of the material to dissipate the energy of deformation. Such materials can find applications in the form of adaptive vibration absorbers (ATVAs), stiffness tunable mounts and variable impedance surfaces. MREs are an important material for automobile giants and became the focus of this research for eventual automatic vibration control, sound isolation, brakes, clutches and suspension systems

Variação sazonal e influência de fatores meteorológicos na incidência de descolamentos regmatógenos da retina na zona centro de Portugal e na Madeira

Objetivos: Analisar a variação sazonal e a influência de fatores meteorológicos na incidência a 5 anos de descolamento regmatógeno da retina (DRR), na região centro do país e região autónoma da Madeira (RAM). Métodos: Série de casos consecutiva, retrospetiva e multicêntrica. Incluíram-se doentes submetidos a cirurgia de DRR no Centro Hospitalar e Universitário de Coimbra e Hospital Doutor Nélio Mendonça entre Janeiro’10 e Dezembro’14. A seleção de casos foi feita através codificação ICD-9-CM e os critérios de inclusão foram: 1)idade ≥18 anos; 2)DRR de novo; 3)reparação cirúrgica do DRR. Consideraram-se critérios de exclusão: 1)DR tracional, exsudativo ou misto; 2)DR antigo ou re-descolamento; 3)soluções de continuidade ou lesões regmatógenas tratadas apenas com laser. Os dados meteorológicos diários das estações de Coimbra, Leiria, Aveiro, Viseu, Guarda, Castelo Branco e Funchal, foram utilizados na análise estatística. Resultados: Foram incluídos 1013 olhos (914 da região centro e 99 da RAM), com idade média 61,84±14,00 anos. Através de um modelo cronológico de regressão linear constatou-se a presença de sazonalidade com picos nos meses de Maio e Setembro. A temperatura média apresentou uma associação marginalmente significativa com a incidência de DRR num modelo biológico de regressão linear considerando os mais fortes preditores de DRR da amostra. Conclusões: Os nossos resultados demonstram que a incidência de DRR se associa a um padrão sazonal significativo que parece ser explicado pela temperatura. Este estudo alerta para a necessidade de um eficaz planeamento em saúde que deverá passar por uma gestão harmoniosa de recursos humanos em épocas de maior incidência.

Variação sazonal e influência de fatores meteorológicos na incidência de descolamentos regmatógenos da retina na zona centro de Portugal e na Madeira

Objetivos: Analisar a variação sazonal e a influência de fatores meteorológicos na incidência a 5 anos de descolamento regmatógeno da retina (DRR), na região centro do país e região autónoma da Madeira (RAM). Métodos: Série de casos consecutiva, retrospetiva e multicêntrica. Incluíram-se doentes submetidos a cirurgia de DRR no Centro Hospitalar e Universitário de Coimbra e Hospital Doutor Nélio Mendonça entre Janeiro’10 e Dezembro’14. A seleção de casos foi feita através codificação ICD-9-CM e os critérios de inclusão foram: 1)idade ≥18 anos; 2)DRR de novo; 3)reparação cirúrgica do DRR. Consideraram-se critérios de exclusão: 1)DR tracional, exsudativo ou misto; 2)DR antigo ou re-descolamento; 3)soluções de continuidade ou lesões regmatógenas tratadas apenas com laser. Os dados meteorológicos diários das estações de Coimbra, Leiria, Aveiro, Viseu, Guarda, Castelo Branco e Funchal, foram utilizados na análise estatística. Resultados: Foram incluídos 1013 olhos (914 da região centro e 99 da RAM), com idade média 61,84±14,00 anos. Através de um modelo cronológico de regressão linear constatou-se a presença de sazonalidade com picos nos meses de Maio e Setembro. A temperatura média apresentou uma associação marginalmente significativa com a incidência de DRR num modelo biológico de regressão linear considerando os mais fortes preditores de DRR da amostra. Conclusões: Os nossos resultados demonstram que a incidência de DRR se associa a um padrão sazonal significativo que parece ser explicado pela temperatura. Este estudo alerta para a necessidade de um eficaz planeamento em saúde que deverá passar por uma gestão harmoniosa de recursos humanos em épocas de maior incidência.

Uso de espectrometria de massa por ionização e dessorção a laser assistida por matriz : tempo de voo (MALDI-TOF MS) para formação de bibliotecas e caracterização da ocupação nodular em soja por estirpes de Bradyrhizobium

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Programa de Pós-Graduação em Biologia Microbiana, 2016.

Utilizzo congiunto di aerofotogrammetria e Laser Scanner terrestre per il rilievo del torrente Ravone di Bologna

La città di Bologna è sicuramente famosa per le sue due torri, ma anche per la fitta rete idraulica ormai nascosta sotto le strade e sotto gli edifici. I primi canali di Bologna furono realizzati tra il XII e il XVI secolo a seguito della costruzione delle due opere fondamentali: le chiuse di San Ruffillo e di Casalecchio. Queste due opere di presa servivano e, servono ancora oggi, ad alimentare i canali del Navile, del Reno, del Savena, del Cavaticcio e delle Moline. Oltre a questi canali alimentati dalle acque dei fiumi, sotto la città di Bologna scorrono torrenti che drenano le acque prevalentemente meteoriche della zona pedecollinare della città, come ad esempio il torrente Ravone. Il presente lavoro di tesi ha come caso di studio proprio quest’ultimo. Il Ravone, in origine, scorreva a cielo aperto attraversando la città, ma per permettere l’urbanizzazione fuori dalle mura, è stato tombato in diversi tratti e in diverse epoche. La scarsità di informazioni riguardo la sua esatta posizione e la mancanza di elaborati grafici in grado di descriverne la sua geometria, ha spinto le autorità a richiedere un accurato rilievo al LARIG dell’UniBo. Le operazioni di rilievo si sono svolte con l’uso di tecniche geomatiche per la modellazione tridimensionale come l’aerofotogrammetria e l’acquisizione con laser scanner terrestre. Al fine di georeferenziare il dato acquisito, si è ricorso a tecniche di rilievo topografico come il posizionamento GNSS e la misurazione di angoli e distanze con stazione totale. I primi capitoli di questo elaborato sono dedicati alla descrizione dei fondamenti teorici della geodesia e delle tecniche di rilievo utilizzate per la restituzione del modello tridimensionale. Gli ultimi capitoli, invece, sono dedicati alla descrizione delle fasi di rilievo e all’analisi dei dati, dedicando particolare attenzione alla georeferenziazione delle nuvole di punti acquisite in ambienti confinati, come i tratti tombati del torrente Ravone.

Membrane Lipid Profile Monitored By Mass Spectrometry Detected Differences Between Fresh And Vitrified In Vitro-produced Bovine Embryos.

Summary This study aimed to evaluate the impact of vitrification on membrane lipid profile obtained by mass spectrometry (MS) of in vitro-produced bovine embryos. Matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) has been used to obtain individual embryo membrane lipid profiles. Due to conditions of analysis, mainly membrane lipids, most favorably phosphatidylcholines (PCs) and sphingomyelins (SMs) have been detected. The following ions described by their mass-to-charge ratio (m/z) and respective attribution presented increased relative abundance (1.2-20×) in the vitrified group: 703.5 [SM (16:0) + H]+; 722.5 [PC (40:3) + Na]+; 758.5 [PC (34:2) + H]+; 762.5 [PC (34:0) + H]+; 790.5 [PC (36:0) + H]+ and 810.5 [PC (38:4) + H]+ and/or [PC (36:1) + Na]+. The ion with a m/z 744.5 [PCp (34:1) and/or PCe (34:2)] was 3.4-fold more abundant in the fresh group. Interestingly, ions with m/z 722.5 or 744.5 indicate the presence of lipid species, which are more resistant to enzymatic degradation as they contain fatty acyl residues linked through ether type bonds (alkyl ether or plasmalogens, indicated by the lowercase 'e' and 'p', respectively) to the glycerol structure. The results indicate that cryopreservation impacts the membrane lipid profile, and that these alterations can be properly monitored by MALDI-MS. Membrane lipids can therefore be evaluated by MALDI-MS to monitor the effect of cryopreservation on membrane lipids, and to investigate changes in lipid profile that may reflect the metabolic response to the cryopreservation stress or changes in the environmental conditions.

Oxidative Stress And Susceptibility To Mitochondrial Permeability Transition Precedes The Onset Of Diabetes In Autoimmune Non-obese Diabetic Mice.

Beta cell destruction in type 1 diabetes (TID) is associated with cellular oxidative stress and mitochondrial pathway of cell death. The aim of this study was to determine whether oxidative stress and mitochondrial dysfunction are present in T1D model (non-obese diabetic mouse, NOD) and if they are related to the stages of disease development. NOD mice were studied at three stages: non-diabetic, pre-diabetic, and diabetic and compared with age-matched Balb/c mice. Mitochondria respiration rates measured at phosphorylating and resting states in liver and soleus biopsies and in isolated liver mitochondria were similar in NOD and Balb/c mice at the three disease stages. However, NOD liver mitochondria were more susceptible to calcium-induced mitochondrial permeability transition as determined by cyclosporine-A-sensitive swelling and by decreased calcium retention capacity in all three stages of diabetes development. Mitochondria H2O2 production rate was higher in non-diabetic, but unaltered in pre-diabetic and diabetic NOD mice. The global cell reactive oxygen species (ROS), but not specific mitochondria ROS production, was significantly increased in NOD lymphomononuclear and stem cells in all disease stages. In addition, marked elevated rates of 2',7'-dichlorodihydrofluorescein (H2DCF) oxidation were observed in pancreatic islets from non-diabetic NOD mice. Using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) and lipidomic approach, we identified oxidized lipid markers in NOD liver mitochondria for each disease stage, most of them being derivatives of diacylglycerols and phospholipids. These results suggest that the cellular oxidative stress precedes the establishment of diabetes and may be the cause of mitochondrial dysfunction that is involved in beta cell death.

Remediation Of 17-α-ethinylestradiol Aqueous Solution By Photocatalysis And Electrochemically-assisted Photocatalysis Using Tio2 And Tio2/wo3 Electrodes Irradiated By A Solar Simulator.

TiO2 and TiO2/WO3 electrodes, irradiated by a solar simulator in configurations for heterogeneous photocatalysis (HP) and electrochemically-assisted HP (EHP), were used to remediate aqueous solutions containing 10 mg L(-1) (34 μmol L(-1)) of 17-α-ethinylestradiol (EE2), active component of most oral contraceptives. The photocatalysts consisted of 4.5 μm thick porous films of TiO2 and TiO2/WO3 (molar ratio W/Ti of 12%) deposited on transparent electrodes from aqueous suspensions of TiO2 particles and WO3 precursors, followed by thermal treatment at 450 (°)C. First, an energy diagram was organized with photoelectrochemical and UV-Vis absorption spectroscopy data and revealed that EE2 could be directly oxidized by the photogenerated holes at the semiconductor surfaces, considering the relative HOMO level for EE2 and the semiconductor valence band edges. Also, for the irradiated hybrid photocatalyst, electrons in TiO2 should be transferred to WO3 conduction band, while holes move toward TiO2 valence band, improving charge separation. The remediated EE2 solutions were analyzed by fluorescence, HPLC and total organic carbon measurements. As expected from the energy diagram, both photocatalysts promoted the EE2 oxidation in HP configuration; after 4 h, the EE2 concentration decayed to 6.2 mg L(-1) (35% of EE2 removal) with irradiated TiO2 while TiO2/WO3 electrode resulted in 45% EE2 removal. A higher performance was achieved in EHP systems, when a Pt wire was introduced as a counter-electrode and the photoelectrodes were biased at +0.7 V; then, the EE2 removal corresponded to 48 and 54% for the TiO2 and TiO2/WO3, respectively. The hybrid TiO2/WO3, when compared to TiO2 electrode, exhibited enhanced sunlight harvesting and improved separation of photogenerated charge carriers, resulting in higher performance for removing this contaminant of emerging concern from aqueous solution.

Morphological Aspects And Cox-2 Expression After Exposure To 780-nm Laser Therapy In Injured Skeletal Muscle: An In Vivo Study.

The effectiveness of low-level laser therapy in muscle regeneration is still not well known. To investigate the effects of laser irradiation during muscle healing. For this purpose, 63 rats were distributed to 3 groups: non-irradiated control group (CG); group irradiated at 10 J/cm(2) (G10); and group irradiated at 50 J/cm(2) (G50). Each group was divided into 3 different subgroups (n=7), and on days 7, 14 and 21 post-injury the rats were sacrificed. Seven days post-surgery, the CG showed destroyed zones and extensive myofibrillar degeneration. For both treated groups, the necrosis area was smaller compared to the CG. On day 14 post-injury, treated groups demonstrated better tissue organization, with newly formed muscle fibers compared to the CG. On the 21(st) day, the irradiated groups showed similar patterns of tissue repair, with improved muscle structure at the site of the injury, resembling uninjured muscle tissue organization. Regarding collagen deposition, the G10 showed an increase in collagen synthesis. In the last period evaluated, both treated groups showed statistically higher values in comparison with the CG. Furthermore, laser irradiation at 10 J/cm(2) produced a down-regulation of cyclooxygenase 2 (Cox-2) immunoexpression on day 7 post-injury. Moreover, Cox-2 immunoexpression was decreased in both treated groups on day 14. Laser therapy at both fluencies stimulated muscle repair through the formation of new muscle fiber, increase in collagen synthesis, and down-regulation of Cox-2 expression.

Evaluation Of Photodynamic Therapy Using A Diode Laser And Different Photosensitizers Against Enterococcus Faecalis.

Photodynamic therapy (PDT) has been proven to be effective in disinfecting root canals. The aim of this present study was to evaluate the effects of PDT on the viability of Enterococcus faecalis using methylene blue (MB) and malachite green (MG) as photosensitizers. Solutions containing E. faecalis (ATCC 29212) were prepared and harvested by centrifugation to obtain cell suspensions, which were mixed with MB and MG. Samples were individually irradiated by the diode laser at a distance of 1mm for 30, 60, or 120 seconds. Colonyforming units (CFU) were determined for each treatment. PDT for 60 and 120 seconds with MG reduced E. faecalis viability significantly. Similar results were obtained when MB was used as photosensitizer. PDT using MB and MG have antibacterial effect against E. faecalis, showing potential to be used as an adjunctive antimicrobial procedure in endodontic therapy.