Influence of water flow rate on shear bond strength of resin composite to Er : YAG cavity preparation

Purpose: To evaluate in vitro the influence of water flow rate on shear bond strength of a resin composite to enamel and dentin after Er:YAG cavity preparation. Methods: Ten bovine incisors were selected and roots removed. Crowns were sectioned in four pieces, resulting in 40 samples that were individually embedded in polyester resin (n=10), and ground to plane the enamel and expose the dentin. The bonding site was delimited and samples were randomly assigned according to cavity preparation: (1) Er:YAG/1.0 mL/minute; (2) Er:YAG/1.5 mL/minute; (3) Er:YAG/2.0 mL/minute and (4) High speed handpiece/bur (control group). Samples were fixed to a metallic device, where composite resin cylinders were prepared. Subsequently, they were stored for 24 hours and subjected to a shear bond strength test (500N at 0.5 mm/minute). Results: Means (MPa) were: enamel: 1: 12.8; 2: 16.8; 3: 17.5; 4: 36.0 and Dentin: 1: 13.6; 2: 18.7; 3: 12.1; 4: 21.3. Data were submitted to ANOVA and Tukey`s test. Adhesion to enamel was more efficient than for dentin. The cavities prepared with conventional bur (control) presented higher statistically significant bond strength values (P<0.05) than for Er:YAG laser for both enamel and dentin. No significant differences were observed between water flow rates employed during enamel ablation. For dentin, the shear bond strength of 2.0 mL/minute water flow rate was lower than for 1.5 mL/minute and 1.0 mL/minute rates. The Er:YAG laser adversely affected shear bond strength of resin composite to both enamel and dentin, regardless of the water flow rate used.

Influence of dentin cavity surface finishing on micro-tensile bond strength of adhesives

The current trend toward minimal-invasive dentistry has introduced innovative techniques for cavity preparation. Chemical vapor deposition (CVD) and laser-irradiation technology have been employed as an alternative to the common use of regular burs in high-speed turbines. Objectives. The purpose of this study was to assess the influence of alternative techniques for cavity preparation on the bonding effectiveness of different adhesives to dentin, and to evaluate the morphological characteristics of dentin prepared with those techniques. Methods. One etch&rinse adhesive (OptiBond FL, Kerr) and three self-etch systems (Adper Prompt L-Pop, 3M ESPE; Clearfil SE Bond, Kuraray; Clearfil S3 Bond, Kuraray) were applied on dentin prepared with a regular bur in a turbine, with a CVD bur in a turbine, with a CVD tip in ultrasound and with an ErCr:YSGG laser. The micro-tensile bond strength (mu TBS) was determined after storage in water for 24 h at 37 degrees C, and morphological evaluation was performed by means of field -emission -gun scanning electron microscopy (Feg-SEM). Results. Feg-SEM evaluation revealed different morphological features on the dentin surface after the usage of both the conventional and alternative techniques for cavity preparation, more specifically regarding smear-layer thickness and surface roughness. CVD bur-cut, CVD ultra-sonoabraded and laser-irradiated dentin resulted in lower mu TBSs than conventionally bur-cut dentin, irrespective of the adhesive employed. Significance. The techniques, such as CVD diamond-bur cutting, CVD diamond ultra-sonoabrasion and laser-irradiation, used for cavity preparation may affect the bonding effectiveness of adhesives to dentin, irrespective of their acidity or approach. (C) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Influence of Er,Cr : YSGG laser treatment on the microtensile bond strength of adhesives to dentin

Purpose: In light of the concept of minimally invasive dentistry, erbium lasers have been considered as an alternative technique to the use of diamond burs for cavity preparation. The purpose of this study was to assess the bonding effectiveness of adhesives to Er,Cr:YSGG laser-irradiated dentin using irradiation settings specific for cavity preparation. Materials and Methods: Fifty-four midcoronal dentin surfaces, obtained from sound human molars, were irradiated with an Er,Cr:YSGG laser or prepared with a diamond bur using a high-speed turbine. One etch-and-rinse (Optibond FL/Kerr) and three self-etching adhesives (Adper Prompt L-Pop/3M ESPE, Clearfil SE Bond/Kuraray, and Clearfil S-3 Bond/Kuraray) were used to bond the composite to dentin. The microtensile bond strength (mu TBS) was determined after 24 h of storage in water at 37 degrees C. The Kruskal-Wallis test was used to determine pairwise statistical differences (p < 0.05). Prepared dentin surfaces, adhesive interfaces, and failure patterns were analyzed using a stereo microscope and Field-emission gun Scanning Electron Microscopy (Feg-SEM). Results: Significantly lower mu TBS was observed to laser-irradiated than to bur-cut dentin (p < 0.05), irrespective of the adhesive employed. Feg-SEM photomicrographs of lased dentin revealed an imbricate patterned substrate and the presence of microcracks at the dentin surface. Conclusion: Morphological alterations produced by Er,Cr:YSGG laser-irradiation adversely influence the bonding effectiveness of adhesives to dentin. Keywords: dentin, adhesion, adhesives, laser, ErCr:YSGG.

Revisiting 2D numerical models for the 19th century outbursts of eta Carinae

We present here new results of two-dimensional hydrodynamical simulations of the eruptive events of the 1840s (the great) and the 1890s (the minor) eruptions suffered by the massive star eta Carinae (Car). The two bipolar nebulae commonly known as the Homunculus and the little Homunculus (LH) were formed from the interaction of these eruptive events with the underlying stellar wind. We assume here an interacting, non-spherical multiple-phase wind scenario to explain the shape and the kinematics of both Homunculi, but adopt a more realistic parametrization of the phases of the wind. During the 1890s eruptive event, the outflow speed decreased for a short period of time. This fact suggests that the LH is formed when the eruption ends, from the impact of the post-outburst eta Car wind (that follows the 1890s event) with the eruptive flow (rather than by the collision of the eruptive flow with the pre-outburst wind, as claimed in previous models; Gonzalez et al.). Our simulations reproduce quite well the shape and the observed expansion speed of the large Homunculus. The LH (which is embedded within the large Homunculus) becomes Rayleigh-Taylor unstable and develop filamentary structures that resemble the spatial features observed in the polar caps. In addition, we find that the interior cavity between the two Homunculi is partially filled by material that is expelled during the decades following the great eruption. This result may be connected with the observed double-shell structure in the polar lobes of the eta Car nebula. Finally, as in previous work, we find the formation of tenuous, equatorial, high-speed features that seem to be related to the observed equatorial skirt of eta Car.

Real-Time Recognition System for Traffic Signs

The aim of this thesis project is to develop the Traffic Sign Recognition algorithm for real time. Inreal time environment, vehicles move at high speed on roads. For the vehicle intelligent system itbecomes essential to detect, process and recognize the traffic sign which is coming in front ofvehicle with high relative velocity, at the right time, so that the driver would be able to pro-actsimultaneously on instructions given in the Traffic Sign. The system assists drivers about trafficsigns they did not recognize before passing them. With the Traffic Sign Recognition system, thevehicle becomes aware of the traffic environment and reacts according to the situation.The objective of the project is to develop a system which can recognize the traffic signs in real time.The three target parameters are the system’s response time in real-time video streaming, the trafficsign recognition speed in still images and the recognition accuracy. The system consists of threeprocesses; the traffic sign detection, the traffic sign recognition and the traffic sign tracking. Thedetection process uses physical properties of traffic signs based on a priori knowledge to detect roadsigns. It generates the road sign image as the input to the recognition process. The recognitionprocess is implemented using the Pattern Matching algorithm. The system was first tested onstationary images where it showed on average 97% accuracy with the average processing time of0.15 seconds for traffic sign recognition. This procedure was then applied to the real time videostreaming. Finally the tracking of traffic signs was developed using Blob tracking which showed theaverage recognition accuracy to 95% in real time and improved the system’s average response timeto 0.04 seconds. This project has been implemented in C-language using the Open Computer VisionLibrary.

Det personliga nätverkets funktion : Etablering och underhåll av presonliga nätverk inom ljuddesign för rörlig bild

The aim of this paper was to discover the functions and workings of personal networks and their advantages for self-employed sound designers and producers whose focus was upon the moving image (film, advertising, tv, etc). Investigations on how entrepreneurs develop their networks were made, as well as inquiries on how these networks are used for generating work. Another important aspect perused was whether or not the networks are dependent on specific geographical locations in order to function. A case study and comparative analysis was undertaken, based upon three qualitative interviews with entrepreneurs whose operations shared several similar characteristics. The results pointed out the importance of constantly making new contacts, and maintaining and managing current ones. There was no evidence that traditional marketing strategies or advertising were used by the interviewees. New commissions were often gained from former clients or acquaintances, or through referrals from them. There are definite advantages to having one's business in the geographical area where one's contacts exist. This also makes it easier to keep up these contacts for future prospects. However, it is very feasible to take on contracts, do the job, and to deliver work to clients in far away locations, due to the high speed internet connections available today.Målet med denna uppsats var att ta reda på hur personliga nätverk fungerar och verkar till fördel för egenföretagande ljuddesigers för rörlig bild (Film, Reklam och tv etc.). Hur entreprenörerna utvecklar nätverken utforskades, även hur de används för att generera arbete samt om nätverken bör vara lokaliserade på en speciell plats för att fungera. En fallstudie och komparativ analys utfördes, baserad på tre kvalitativa intervjuer med entreprenörer vars verksamheter liknade varandra på flera plan. Resultatet påvisade vikten av att hela tiden skapa nya kontakter och underhålla befintliga sådana. Inget tydde på att traditionell marknadsföring eller reklam används. Nya uppdrag uppkommer oftast genom tidigare kunder, kontakter eller rekommendationer från dessa. Det finns klara fördelar med att bedriva sin verksamhet i det område där kontakterna finns och det är även lättare att underhålla dem i dessa fall. Det är dock fullt möjligt att åta sig, utföra och leverera uppdrag för befintliga kontakter på långt håll tack vare dagens snabba internetuppkopplingar.

Rate Scheduling for HSDPA in UMTS

The introduction of a new technology High Speed Downlink Packet Access (HSDPA) in the Release 5 of the 3GPP specifications raises the question about its performance capabilities. HSDPA is a promising technology which gives theoretical rates up to 14.4 Mbits. The main objective of this thesis is to discuss the system level performance of HSDPAMainly the thesis exploration focuses on the Packet Scheduler because it is the central entity of the HSDPA design. Due to its function, the Packet Scheduler has a direct impact on the HSDPA system performance. Similarly, it also determines the end user performance, and more specifically the relative performance between the users in the cell.The thesis analyzes several Packet Scheduling algorithms that can optimize the trade-off between system capacity and end user performance for the traffic classes targeted in this thesis.The performance evaluation of the algorithms in the HSDPA system are carried out under computer aided simulations that are assessed under realistic conditions to predict the results as precise on the algorithms efficiency. The simulation of the HSDPA system and the algorithms are coded in C/C++ language

Evolution of artificial defects during shape rolling

Very often defects are present in rolled products. For wire rods, defects are very deleterious since the wire rods are generally used directly in various applications. For this reason, the market nowadays requires wire rods to be completely defect-free. Any wire with defects must be rejected as scrap which is very costly for the production mill. Thus, it is very important to study the formation and evolution of defects during wire rod rolling in order to better understand and minimize the problem, at the same time improving quality of the wire rods and reducing production costs. The present work is focused on the evolution of artificial defects during rolling. Longitudinal surface defects are studied during shape rolling of an AISI M2 high speed steel and a longitudinal central inner defect is studied in an AISI 304L austenitic stainless steel during ultra-high-speed wire rod rolling. Experimental studies are carried out by rolling short rods prepared with arteficial defects. The evolution of the defects is characterised and compared to numerical analyses. The comparison shows that surface defects generally reduce quicker in the experiments than predicted by the simulations whereas a good agreement is generally obtained for the central defect.

An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling

The surface failure characteristics of different work roll materials, i.e. High Speed Steel, High Chromium Iron and Indefinite Chill Iron, used in the finishing stands of a hot strip mill have been investigated using stereo microscopy, 3D optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the surface failure mechanisms of work rolls for hot rolling are very complex, involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. Despite the differences in chemical composition and microstructure, the tribological response of the different work roll materials was found to be strongly dependent on the material microstructure and especially the presence and distribution of microstructural constituents, such as the different carbide phases and graphite (in the case of Indefinite Chill Iron). Cracking and chipping of the work roll surfaces, both having a negative impact on work roll wear, are strongly influenced by the presence of carbides, carbide networks and graphite in the work roll surface. Consequently, the amount of carbide forming elements as well as the manufacturing process must be controlled in order to obtain an optimised microstructure and a predictable wear rate.

1998 Yearbook

Sept. 1998; 72 pages; pages 69-72 (Yearzine) b&w, color photographs TOC: Reflections…1 / Dedication…2 / Table of Contents…3 / Message from the President…4 / Message from the Student Government President…5 / The Deans…6 / Robert Francis Kennedy…7 / Student Activities Club Life…8 / Student Activities Club Fair…10 / We Build Potential…12 / Student Government Association 1997/98…14 / Poetry Writing my way out of the Ghetto…16 / Multi-Cultural Appreciation Week 16A-D / Dr. Martin Luther King Jr….17 / Future Leaders Early Childhood Learning Center…18 / Poetry + 5K Race…20 / The Class of 1997/98…21 / Message from the Yearbook Committee…61 / Tribute to Donald Barker Health Center…62 / Poetry Stepping Out…63 / Credits…64 Credits: PROJECT SUPERVISOR: IRENE SOSA; PROJECT COORDINATOR: EDWARD HOLLINS; ASST. PROJECT COORDINATORS: VINCENT COUSIN, ALLEN SCRIBNER, MADODHREE YAMRAJ; EVENT PHOTOGRAPHERS: VINCENT COUSIN, ALLEN SCRIBNER, RANDY FADER-SMITH; GRADUATE PHOTOGRAPHERS: SAMUEL LEE, LUIS REYES; POETRY: MATTHEW JOFFE, LISA KREMENS, THOMAS MCCRAY, JR. Special Thanks: -THE STAFF OF STUDENT LIFE & DEVELOPMENT (FRAN, GREGORY, LUIS, MILLIE) -ENOCK CHARLOTIN -DR. NOMA KRASNEY -HIGH SPEED PHOTO (LOUIS, FERNANDO, JAMES -THANKS GUYS, GREAT JOB!) -WARREN COOPER (TAYLOR PUBLISHING) -ANILA JOHN (S.G.A OFFICE MANAGER) - RON BOERKE (EVENTS OFFICE)

Acumulação de capacidades tecnológicas e mecanismos de aprendizagem: um estudo comparativo em duas subsidiárias de empresas multinacionais do setor de tecnologias da informação e comunicação no Brasil

Esta dissertação examina o relacionamento entre o acúmulo de capacidades tecnológicas e os mecanismos de aprendizagem tecnológica em subsidiárias de empresas multinacionais inseridas em economias em desenvolvimento. Este relacionamento é analisado por meio de estudo de caso comparativo de duas subsidiárias do setor de tecnologia da informação e comunicação brasileiro, de diferente países de origem, para as tecnologias associadas ao acesso à internet em alta velocidade, no período de 2004 a 2009. A literatura referente ao desenvolvimento de capacidades tecnológicas em organizações inseridas em economias emergentes evoluiu consideravelmente nos últimos anos, descrevendo vários exemplos da evolução destas capacidades tecnológicas. Porém, ainda são raros os estudos que examinam este processo em subsidiárias de empresas multinacionais presentes em economias emergentes e,mais raros ainda, os estudos que examinam os relacionamentos entre estas trajetórias de acumulação e os seus mecanismos de aprendizado em duas subsidiárias. Com o objetivo de contribuir para o preenchimento dessa lacuna, esta pesquisa buscou enriquecer este debate baseando-se em evidências empíricas primárias e secundárias, para explorar este relacionamento com bastante profundidade e pôde verificar que: 1. Em ambas as subsidiárias pesquisadas houve acumulação de capacidades tecnológicas. Porém, houve uma forte distinção entre estas empresas estudadas em termos da natureza e velocidade de acumulação de capacidades tecnológicas. 2. Também pôde-se identificar um intenso uso de mecanismos intra-organizacionais de fontes internas e de interorganizacionais de fontes externas de aprendizagem tecnológica. Porém, esta característica também apresentou uma grande variabilidade de diversidade e intensidade do uso destes mecanismos, para acumulação de capacidades tecnológicas ao nível da subsidiária. E, a partir destas evidências, pode-se concluir que os diferentes mecanismos de aprendizado tecnológico utilizados pelas organizações inseridas em economias em desenvolvimento desempenham um papel de fundamental relevância não somente para a natureza das capacidades tecnológicas acumuladas, mas também para a intensidade de acumulação. Assim, desta conclusão pode-se interpretar que a Alcatel-Lucent, através de seus esforços de aprendizado tecnológico, está melhor preparada para um contexto competitivo caracterizado por inovações tecnológicas que a ZTE Corporation. Mas este contexto competitivo muitas vezes não se forma em economias emergentes, como a brasileira, que devido à baixa competição e uma crescente necessidade de resultados econômicos de curto prazo faz com que a opção por empresas com o enfoque de custos (ou capacidades operacionais) seja mais valorizada do que empresas com o enfoque de desenvolvimento de capacidades inovadoras capazes de produzir tecnologias. Logo, os resultados desta dissertação sugerem aos gestores destas empresas: (1) a necessidade de um contínuo engajamento em busca de novas fontes de aprendizado tecnológico interno e externo às suas respectivas organizações, de forma a sustentar e acumular novas capacidades tecnológicas operacionais e inovadoras, (2) a importância da qualidade e intensidade dos diversos tipos de relacionamentos e interações internos e externos a estas organizações, de forma a intensificar estes relacionamentos de aprendizado em tecnologias inexistentes nestas organizações. Os resultados desta dissertação também permitem apontar sugestões para gestores governamentais, visto que, no “Plano Nacional de Banda larga”, em desenvolvimento pelo governo federal brasileiro, (1) deve-se incentivar o fortalecimento das parcerias e interações entre as diversas organizações do setor, como as subsidiárias de EMN, as operadoras e centros tecnológicos e universidades locais, de forma a criar projetos mútuos de pesquisa e desenvolvimento de novas tecnologias no setor e, por conseqüência, um maior desenvolvimento tecnológico setorial e (2) buscar através da regulação do setor, que as empresas sejam incentivadas a buscar novos e melhores mecanismos de aprendizagem de forma a consolidar e evoluir as suas capacidades tecnológicas, visando o desenvolvimento tecnológico setorial.

Trabalhar para que?: percepções sobre trabalho entre jovens de diferentes estratos sociais

O atual mundo do trabalho vem sofrendo transformações importantes nas últimas décadas. O cenário econômico em constante mudança, as inovações tecnológicas em alta velocidade e a forte competição global são fatores importantes que têm influenciado de forma decisiva os mercados, as empresas e o conceito de trabalho de forma geral. Neste contexto, é inegável a relevância que o trabalho exerce em nossas vidas, e a busca pelo entendimento de seus sentidos, significados e concepções vêm despertando o interesse dos estudiosos do campo dos estudos organizacionais há alguns anos. A produção científica brasileira também vem buscando conhecer, por meio de pesquisas empíricas e/ou teóricas, como o trabalho se organiza e se estabelece em nossas vidas. Nesta pesquisa, tem-se como objetivo conhecer como os jovens, que já nasceram neste contexto de mudança, percebem o trabalho em suas vidas. A partir de um estudo qualitativo, esta pesquisa, que incluiu entrevistas e desenhos com 92 jovens de diferentes estratos sociais, mostrou que existe uma homogeneidade de percepções sobre o trabalho. Em outras palavras, independente do estrato social ao qual pertencem, para a grande maioria destes jovens o trabalho é percebido exclusivamente como meio para se ganhar dinheiro e consumir, e não como um fim em si mesmo. Os discursos destes jovens reforçam a importância que o dinheiro exerce em suas vidas, sendo inclusive o grande protagonista na conquista da felicidade. Com base em uma perspectiva crítica de análise, argumenta-se que o trabalho não tem centralidade na vida destes jovens, e a centralidade que se estabelece no discurso dos participantes é sim o papel que o dinheiro exerce em nossa sociedade do consumo

Trem de alta velocidade RJ-SP: estudo de caso sobre sua não implementação durante os governos Lula e Dilma

This work refers to one of the greatest infrastructure projects planned by the Federal Public Administration entitled Trem de Alta Velocidade RJ-Campinas (TAV Brasil) [High Speed Rail Rio de Janeiro – Campinas], also know as bullet train. The intent of this research is not to explore the technical issues of the project bu the description of some details contributes for a better understanting of the evolved technology. The focus of this work is found under the actions promoted by diverse political actors in such enterprise as well as the context which made the public grant not possible along the two mandates of President Lula and the first one of President Dilma Rousseff. This contemporary matter required a huge documentary investigation performed by available material on the internet, news report of the most important press vehicles in the country, essays and articles published by experts. Some people involved in this policy process were interviewed. These inputs enriched the data explaining the conceived actions and structure of the project by the federal government. The results and final considerations target the complexity of the project and the TAV auctions failure from 2010 to 2014, suggesting further researches concerning the retaking of the bullet train project.