Influence of the grinding wheel's dive speed on the damage of rectified hardened steels

The world tendency is the increase of the productivity and the production of pieces more and more sophisticated, with high degree of geometric and dimensional tolerances, with good surface finish and low cost. Rectification is responsible for the final finish in the machining process of a material. However, damages generated in this production phase affect all the resources used in the previous processes. Great part of the problems happennig in the rectification process is due to the enormous temperature generated in this activity because of the machining conditions. The dive speed, which is directly related to the productivity, is considered responsible for the damages that occur during rectification, limiting its values to those that do not cause such damages. In this work, through the variation of the dive speed in the process of cylindrical grinding of type ABNT D6 steel, rationalizing the application of two cutting fluids and using a CBN (cubic boron nitrate) abrasive wheel with vitrified blond, the influence of the dive speed on the surface damages of hardened steels was evaluated. The results allowed to say that the dive speed, associated to an efficient cooling and lubrication, didn't provoke thermal damages (including heated zones, cracks and tension stresses) to the material. Residual stresses and the roughness of rectified materials presented a correlation with the machining conditions. The work concluded that it is possible to increase the productivity without provoking damages in the rectified components.

Evaluation of the kinetics of xylose formation from dilute sulfuric acid hydrolysis of forest residues of Eucalyptus grandis

Dilute acid hydrolysis studies were performed on forest residues of Eucalyptus grandis, in a cylindrical reactor of stainless steel. The kinetics of this hydrolysis reaction was investigated employing 0.65% sulfuric acid, a residue/acid solution ratio of 1/9 (w/w), temperatures of 130, 140, 150, and 160 degrees C, and reaction times in the range 20-100 min. The results showed that, under the optimized conditions of acid hydrolysis employed in this study, the variables temperature and reaction time had a strong influence on hemicellulose removal and a small influence on the degree of lignin and cellulose removal. The highest xylose extraction yield was 87.6% attained at 160 degrees C, after 70 min reaction time, simultaneously with the formation of decomposition products, namely 2.8% acetic acid, 0.6% furfural, and 0.06% 5-hydroxymethylfurfural. A similar xylose extraction yield (82.8%) was observed at 150 degrees C after 100 min, with the formation of 3.2% acetic acid, 1.0% furfural, and 0.07% 5-hydroxymethylfurfural. The kinetic parameters determined at 130, 140, 150, and 160 degrees C for degradation of xylan present in the hemicellulose of the eucalyptus forest residue during the formation of xylose were the first-order reaction rate constants (k) for each temperature, 1.22 x 10(-4), 2.12 x 10(-4), 5.43 x 10(-4), and 9.05 x 10(-4) s(-1), respectively, and an activation energy (E-a) of 101.3 kJ mol(-1).

Notes on vibration control of a micro/macromanipulator mounted on a flexible structure

The objective of this study is to describe the design and the implementation of an experimental set-up used to study the dynamics, the experimental identification, and the active vibration control of a flexible structure mounted manipulator system. The system consists of a three-degree-of-freedom cylindrical manipulator system with a flexible link on its tip. A two-degree-of-freedom polar rigid manipulator is mounted on the flexible macromanipulator. The dynamic modelling and experimental modal analysis identification in the frequency domain are being applied to design active digital control strategies for the micro-manipulator system to damp the mechanical vibrations of the flexible structure on the tip of the macro-manipulator system.

Effect of target bias on magnetic field enhanced plasma immersion ion implantation

Recent studies have demonstrated that sheath dynamics in plasma immersion ion implantation (PIII) is significantly affected by an external magnetic field, especially in the case when the magnetic field is parallel to the workpiece surface or intersects it at small angles. In this work we report the results from two-dimensional, particle-in-cell (PIC) computer simulations of magnetic field enhanced plasma immersion implantation system at different bias voltages. The simulations begin with initial low-density nitrogen plasma, which extends with uniform density through a grounded cylindrical chamber. Negative bias voltage is applied to a cylindrical target located on the axis of the vacuum chamber. An axial magnetic field is created by a solenoid installed inside the target holder. A set of simulations at a fixed magnetic field of 0.0025 T at the target surface is performed. Secondary electron emission from the target subjected to ion bombardment is also included. It is found that the plasma density around the cylindrical target increases because of intense background gas ionization by the electrons drifting in the crossed E x B fields. Suppression of the sheath expansion and increase of the implantation current density in front of the high-density plasma region are observed. The effect of target bias on the sheath dynamics and implantation current of the magnetic field enhanced PIII is discussed. (C) 2007 Elsevier B.V. All rights reserved.

Numerical simulation of magnetic field enhanced plasma immersion ion implantation

The behavior of plasma and sheath characteristics under the action of an applied magnetic field is important in many applications including plasma probes and material processing. Plasma immersion ion implantation (PIII) has been developed as a fast and efficient surface modification technique of complex shaped three-dimensional objects. The PIII process relies on the acceleration of ions across a high-voltage plasma sheath that develops around the target. Recent studies have shown that the sheath dynamics is significantly affected by an external magnetic field. In this work we describe a two-dimensional computer simulation of magnetic field enhanced plasma immersion implantation system. Negative bias voltage is applied to a cylindrical target located on the axis of a grounded cylindrical vacuum chamber filled with uniform nitrogen plasma. An axial magnetic field is created by a solenoid installed inside the cylindrical target. The computer code employs the Monte Carlo method for collision of electrons and neutrals in the plasma and a particle-in-cell (PIC) algorithm for simulating the movement of charged particles in the electromagnetic field. Secondary electron emission from the target subjected to ion bombardment is also included. It is found that a high-density plasma region is formed around the cylindrical target due to the intense background gas ionization by the magnetized electrons drifting in the crossed ExB fields. An increase of implantation current density in front of high density plasma region is observed. (C) 2007 Elsevier B.V. All rights reserved.

Distribuição diária das atividades comportamentais dos camarões marinhos Farfantepenaeus subtilis (Pérez Farfante, 1967) e Litopenaeus schmitti (Burkenroad, 1938) em condições laboratoriais

Marine aquaculture has developed in the last decades all over the world, especially related to shrimp management. In Brazil, the introduction of the species Litopenaeus vannamei has contributed to the success of the activity, even if there are problems associated with the management of a exotic species, such as new diseases and ecological pressure on native species. It has been emphasized the need of research for developing new methodology that will allow native species management, being the most important Farfantepenaeus subtilis and Litopenaeus schmitti. Most knowledge obtained from research with those species has generally used a technical approach and mainly focused feeding process. There are no specific behavioral data on their activity pattern which should be of great importance for the use of native species on commercial culture farms. So, it was our objective to study and compare the daily distribution of behavioral activities of the marine shrimp species Litopenaeus schmitti and Farfantepenaeus subtilis. Forty animals of each species, 5 individuals per aquarium, were maintained in aquaria containing 200L of sea water under continuous aeration and filtration. They were marked individually and were observed by the instantaneous focal time sampling, along 10 continuous days, in 6 daily 15 min observation windows, every two hour. In each window, behaviors and location position of the animals in the aquarium were registered at 1 min intervals. Food was offered 3 times a day, representing 10% of each aquarium biomass. Aquaria were maintained in artificial photoperiod, 12hour light/l2 hour dark, 4 aquaria in light cycle equivalent to the environmental one (light from 06:00 to 17:59 h and dark from 18:00 to 05:59 h) and the other 4 in the reverse light cycle (light from 18:00 to 05:59 h and dark from 06:00 to 17:59 h) to allow sequential behavioral observation in both phases of the 24 hour cycle. There was a clear distinction between the distribution of behavioral activities of F. subtilis and L. schmitti in the two phases. The activity pattern of Farfantepenaeus subtilis demonstrates that species has prominently night habits and a burying pattern during the light cycle. Exploration, inactivity and swimming were the most common activities. The behavioral pattern of Litopenaeus schmitti indicates that species is active along both phases of the light cycle, and the most evident behaviors were exploration, inactivity and swimming

Thin films generated by plasma immersion ion implantation and deposition of hexamethyldisilazane mixed with nitrogen in different proportions

In this work, it was used a plasma system composed of a cylindrical stainless steel reactor, a radio-frequency (13.56MHz) power source fixed at either 25 W or 70 W, a power source with a negative bias of 10kV and a 100Hz pulse. The system worked at an operational pressure of 80mTorr which consisted of varying concentrations of the monomer HMDSN and gaseous nitrogen in ratios: HMDSN (mTorr)/nitrogen (mTorr) from 70/10 to 20/60 in terms of operational pressure. The structural characterization of the films was done by FTIR spectroscopy. Absorptions were observed between 3500 cm(-1) to 3200 cm(-1), 3000 cm(-1) to 2900 cm(-1), 2500 cm(-1) to 2000 cm(-1), 1500 cm(-1) to 700 cm(-1), corresponding, respectively, to OH radicals, C-H stretching bonds in CH2 and CH3 molecules, C-N bonds, and finally, strain C-H bonds, Si-CH3 and Si-N groups, for both the 70 W and the 25 W. The contact angle for water was approximately 100 degrees and the surface energy is near 25mJ/m(2) which represents a hydrophobic surface, measured by goniometric method. The aging of the film was also analyzed by measuring the contact angle over a period of time. The stabilization was observed after 4 weeks. The refractive index of these materials presents values from 1.73 to 1.65 measured by ultraviolet-visible technique.

Amorphous hydrogenated carbon films treated by SF(6) plasma

This work was performed to verify the chemical structure, mechanical and hydrophilic properties of amorphous hydrogenated carbon films prepared by plasma enhanced chemical vapor deposition, using acetylene/argon mixture as monomer. Films were prepared in a cylindrical quartz reactor, fed by 13.56 MHz radiofrequency. The films were grown during 5 min, for power varying from 25 to 125 W at a fixed pressure of 9.5 Pa. After deposition, all samples were treated by SF(6) plasma with the aim of changing their hydrophilic character. Film chemical structure investigated by Raman spectroscopy, revealed the increase of sp(3) hybridized carbon bonds as the plasma power increases. Hardness measurements performed by the nanoindentation technique showed an improvement from 5 GPa to 14 GPa following the increase discharge power. The untreated films presented a hydrophilic character, which slightly diminished after SF(6) plasma treatment.

Effect of electron magnetic trapping in a plasma immersion ion implantation system

In this work we describe a two-dimensional computer simulation of magnetic field enhanced plasma immersion implantation system. Negative bias voltage of 10.0 kV is applied to a cylindrical target located on the axis of a grounded vacuum chamber filled with uniform nitrogen plasma. A pair of external coils creates a static magnetic field with main vector component along the axial direction. Thus, a system of crossed ExB field is generated inside the vessel forcing plasma electrons to rotate in azimuthal direction. In addition, the axial variation of the magnetic field intensity produces magnetic mirror effect that enables axial particle confinement. It is found that high-density plasma regions are formed around the target due to intense background gas ionization by the trapped electrons. Effect of the magnetic field on the sheath dynamics and the implantation current density of the PIII system is investigated. By changing the magnetic field axial profile (varying coils separation) an enhancement of about 30% of the retained dose can be achieved. The results of the simulation show that the magnetic mirror configuration brings additional benefits to the PIII process, permitting more precise control of the implanted dose.

Evaluation of the fretting fatigue behaviour of commercially pure titanium

Fretting fatigue occurs when the contact surfaces of two components undergo small oscillatory movement while they are subjected to a clamping force. A cyclic external load gives rise to the early initiation of fatigue cracks, thus reducing their service life. In this paper, the fretting fatigue behaviour of commercially pure titanium flat samples (1.5 mm thick) is evaluated. A fretting device composed of a frame, load cell, and two screw-mounted cylindrical fretting pads with convex extremities was built and set to a servo-hydraulic testing machine. The fatigue tests were conducted under load control at a frequency of 10 Hz and stress ratio R = 0.1, with various contact load values applied to the fretting pads. Additional tests under inert environment allowed assessing the role of oxidation on the wear debris formation. The fracture surfaces and fretting scars were analysed via scanning electron microscopy in order to evaluate the surface damage evolution and its effect on the fatigue crack features. The effect of the fretting condition on the S-N curve of the material in the range of 10(4)-10(6) cycles is described. Fatigue crack growth calculations allowed estimating the crack initiation and propagation lives under fretting conditions. The effect of the fretting condition in fatigue life is stronger for the lower values of cyclic stress and does not seem to depend on the contact loading value.

Tropical dermatology: Marine and aquatic dermatology

Dermatoses caused by marine organisms are frequently seen in dermatology clinics worldwide. Cutaneous injuries after exposure to marine environments include bacterial and fungal infections and lesions caused by aquatic plants and protists. Some of these diseases are well known by dermatologists, such as Vibrio vulnificus septicemia and erysipeloid, but others are uncommon, such as envenomation caused by ingestion or contact with certain dinoflagellates or cyanobacteria, which are associated with rashes that can begin Within minutes after exposure. Many marine/aquatic invertebrates, such as sponges, cnidarians, echinoderms, crustaceans, and mollusks, are associated with different kinds of dermatologic lesions that call vary from irritant or allergic contact dermatitis to physical trauma and envenomations. These cutaneous lesions May result in mild local reactions or can be associated with severe systemic reactions. Invertebrate animals, such as cnidarians, sea urchins, and worms, and aquatic vertebrates, such as venomous fishes and stingrays, are commonly associated with skin lesions in many countries, where they call constitute occupational dermatoses among fishermen and scuba divers, but they can also be observed among persons who contact these animals in kitchens or beaches. The presence of unusual lesions, a recent travel history, and/or a report of contact with an aquatic environment (including ownership of a marine or freshwater aquarium) should alert the dermatologist to the etiology of the cutaneous problems. (J Am Acad Dermatol 2009;61:733-50.)

Avaliando o impacto da utilização de renderizações panorâmicas para a navegação em ambientes virtuais

Panoramic rendering is the visualization of three-dimensional objects in a virtual environment through a wide viewing angle. This work investigated if the use of panoramas is able to promote faster searches in a virtual environment. Panoramas allow the presentation of space through less need to change the orientation of the camera, especially for the case of projections spanning 360º surrounding the user, which can benefit searching. However, the larger the angle, more distorted is the visualization of the environment, causing confusion in navigation. The distortion is even bigger when the user changes the pitch of the camera, by looking up or down. In this work we developed a technique to eliminate specifically the distortions caused by changes in pitch, which was called hemispheric projection. Experiments were done to evaluate the performance of search navigation through perspective, cylindrical and hemispherical projections. The results indicate that navigating with perspective projection is superior than navigating with panoramic projections, possibly due to factors such as (i) lack of experience of the participants in understanding the scenes displayed as panoramas, (ii) the inherent presence of distortion in panoramic projections and (iii) a lower display resolution because the objects are presented in smaller sizes in panoramic projections, making the perception of details more difficult. However, the hemispherical projection was better than the cylindrical, indicating that the developed technique provides benefits for navigation compared to current techniques of panoramic projection. The hemispheric projection also provided the least amount of changes of camera orientation, which is an indication that the hemispheric projections may be particularly useful in situations where there are restrictions on the ease to change the orientation. Future research will investigate the performance of cameras interactions on slower devices, such as using only keyboard, or brain-machine interfaces

Macrofauna de ambientes não consolidados adjacentes à recifes da área de proteção ambiental dos recifes de corais Rio Grande do Norte, Brasil

This study aimed to characterize, for the first time, the benthic invertebrates that inhabit the region of soft bottoms adjacent to the APARC reefs in order to situate them as an important component of infralittoral coastal areas of Northeast Brazil. Soft bottoms areas of APARC corresponds to infralittoral zones vegetated by seagrass Halodule wrightii and unvegetated infralittoral zones, both subjected to substantial hydrodynamic stress. Through scuba diving, biological and sedimentary samples of both habitats were analyzed, with a cylindrical sampler. We identified 6160 individuals belonging to 16 groups and 224 species. The most abundant macrofaunal group was Polychaeta (43%), followed by Mollusca (25%) and Crustacea (14%), what was expected for these environments. In the first chapter, regarding vegetated areas, we tested three hypotheses: the existence of differences in the faunal structure associated with H. wrightii banks submitted to different hydrodynamic conditions; the occurrence of minor temporal variations on the associated macrofauna of banks protected from hydrodynamic stress; and if the diversity of macrofauna is affected by both benthophagous predators and H. wrightii biomass. It was observed that macrofauna associated at the Exposed bank showed differences in structure when comparing the Protected bank, the granulometry of the sediments, that co-varies with the hydrodynamism, was the cause of these variations. The results also pointed to a lower temporal variation in the macrofaunal structure on the Protected bank and a negative relation between macrofaunal and benthophagous fish abundance. At the Exposed bank, a greater faunal diversity was observed, probably due to the higher seagrass biomass. The second chapter compares the vegetated and non-vegetated areas in order to test the hypothesis that due to greater seasonal stability in tropical environments, seagrass structure would act to distinguish the vegetated and non-vegetated areas macrofauna, over time. It was also expected that depositivores were the most representative invertebrates on non-vegetated environments, on the assumption that the seagrass bank would work as a source of debris to adjacent areas, enriching them. Considering all sampling periods, the total macrofauna abundance and diversity were higher in vegetated areas, when compared to non-vegetated ones. Seasonally, the structural complexity provided by Halodule differentiated more clearly the fauna from vegetated and non-vegetated areas, but only at the climatic extremes, i.e. Dry season (extreme climatic stability, with low hydronamism variation) and Rainy season (great hydrodynamism variation and probably vegetated bank burial). Furthermore, the high organic matter levels measured in the sandy banks coincided with an outstanding trophic importance of deposit feeders, proving the debris-carrying hypothesis. The last chapter focused on the non-vegetated areas, where we tested that the hypothesis infaunal halo in tropical reefs depending on local granulometry. In this context, we also tested the hypothesis that benthophagous fish predation would have an effect on the low abundance of macrofaunal groups due to the high hydrographic stress, thus allowing other predatory groups to have greater importance in these environments. Proving the hypothesis, no spatial variation, both on abundance families neither on community structure, occur along distance of the edge reefs. However, we found that complex combinations of physical factors (grain size and organic matter levels originated from local hydronamic conditions) covary with the distance from the reefs and has stronger influence on macrofauna than considered biological factors, such as predation by benthophagous fishes. Based on the main results, this study shows that unconsolidated areas around APARC reefs are noteworthy from an ecological and conservational point of view, as evidenced by the biota-environment and organismal relations, never before described for these areas

Facoemulsificação por córnea clara no meridiano mais curvo

OBJETIVOS: Avaliar o efeito da facoemulsificação com incisão em córnea clara no meridiano mais curvo sobre a magnitude do astigmatismo ceratométrico pré-operatório. Mapear a magnitude do astigmatismo cirurgicamente induzido por incisões nas posições nasal (N), temporal (T), temporal superior (TS) e temporal inferior (TI). MÉTODOS: Foi realizado estudo ceratométrico prospectivo em 48 olhos de 48 pacientes, submetidos a facoemulsificação com incisão do meridiano mais curvo. As medidas ceratométricas foram realizadas no pré-operatório e um mês após a realização da cirurgia. O astigmatismo cirurgicamente induzido foi determinado pelo método das coordenadas retangulares em 10 passos, modificado. RESULTADOS: Foram operados 21 olhos direitos e 27 olhos esquerdos e, de acordo com a posição das incisões em córnea clara, foram divididos em: 16 olhos N, 4 olhos T, 22 olhos TS, 6 olhos TI. A média da ametropia cilíndrica pré-operatória foi de 1,06D ± 0,65 e a pós-operatória de 0,89D ± 0,80. Houve diminuição estatisticamente significativa no astigmatismo corneal preexistente (p=0,016). A média total de astigmatismo cirurgicamente induzido foi de 0,94D ± 0,56. em relação aos grupos o astigmatismo cirurgicamente induzido foi de 1,06D ± 0,66 em N, 0,87D ± 0,20 em T, 0,95D ± 0,55 em TS e 0,61D ± 0,25 em TI. Não houve diferença estatística com relação ao astigmatismo cirurgicamente induzido nos grupos N, T, TS e TI (p=0,426). CONCLUSÃO: A técnica se mostrou efetiva na redução do astigmatismo ceratométrico pré-operatório. A média do astigmatismo cirurgicamente induzido foi de 1,06D ± 0,66 em N, 0,95D ± 0,55 em TS, 0,61D ± 0,25 em T e 0,87D ± 0,20 em TI.

Vocal Cysts: Clinical, Endoscopic, and Surgical Aspects

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)