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Artykuły w czasopismach na temat "HEMISPHERICAL TIP"
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DAVIES, KERRIE A., WEIMIN YE, GARY S. TAYLOR, SONJA SCHEFFER, F. BARTHOLOMAEUS i ROBIN M. GIBLIN-DAVIS. "Nematodes from galls on Myrtaceae. XI. Descriptions of five new species of Fergusobia from Australia". Zootaxa 4399, nr 1 (20.03.2018): 1. http://dx.doi.org/10.11646/zootaxa.4399.1.1.
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Five new species of Fergusobia are described. Fergusobia janetae Davies n. sp. is characterized by the combination of an arcuate to straight, spindle-shaped parthenogenetic female with a relatively small oesophageal gland, an extensile uterus and a conoid tail, an arcuate infective female with a bluntly rounded tail tip, and a C-shaped male with an arcuate to angular spicule and bursa arising at more than 90% of body length. Fergusobia robustae Davies n. sp. is characterized by the combination of a small, C-shaped parthenogenetic female with a short cylindroid tail with a broadly rounded tip; an arcuate to C-shaped, relatively broad, infective female with a tail tip that is almost hemispherical; and an arcuate male with a strong angular spicule and a bursa arising at 30–40% of body length. Fergusobia pruinosae Davies n. sp. is characterized by the combination of a medium sized, open C-shaped, parthenogenetic female in which the cuticle does not swell upon fixation, with a strongly sclerotised stylet, with a more or less narrowly conoid tail with a bluntly or broadly rounded tip; infective female that is arcuate to J-shaped with a notched tail tip; and open C-shaped males with stout, angular spicules and bursa arising near the secretory/excretory pore. Fergusobia pauciflorae Davies n. sp. is characterized by the combination of a medium sized, arcuate, parthenogenetic female with a small stylet, and a conoid tail with a bluntly rounded tip; a small, open C to J-shaped infective female with a broadly rounded to almost hemispherical tail tip; and straight to arcuate males with stout, angular spicules and bursa at ~70% of body length anterior to the cloaca. Fergusobia obliquae Davies n. sp. has a relatively broad, arcuate, parthenogenetic female having a small but strongly sclerotised stylet, and a short conoid tail with a bluntly rounded tip; an arcuate, infective female with an almost hemispherical tail tip; and C-shaped males with arcuate to angular (not heavily sclerotised) spicules and bursa arising 50–80% of body length anterior to tail. Sequencing of the 18S and 28S rDNA domains for F. janetae n. sp. and of mitochondrial DNA cytochrome oxidase subunit I (mtCOI) for F. pauciflorae n. sp. confirm that they are distinct species.
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Christman, Locke. "Optimization of LaB6 Cathode Tip Shape for Maximum Brightness Over Lifetime". Proceedings, annual meeting, Electron Microscopy Society of America 48, nr 1 (12.08.1990): 430–31. http://dx.doi.org/10.1017/s0424820100180902.
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LaB6 cathodes are widely used as high brightness cathodes in electron microscopy and are capable of providing about five times the brightness of a tungsten hairpin filament. It is desirable to optimize the shape of the LaB6 tip to provide the highest possible brightness and to insure that this high level of brightness is maintained over the life of the cathode.It is well known that a high brightness electron beam is important in obtaining ultimate resolution in electron microscopy. Brightness is defined as the current density per unit solid angle, or amperes per square centimeter per steradian, in the electron beam. In electron microscopy, one would like to obtain the maximum possible brightness for the particular electron gun. Brightness is a conserved quantity, meaning that as the beam traverses the column, brightness can not be gained, only lost. Therefore, one must begin with the brightest possible cathode in order to obtain the best possible electron beam brightness.Much work has been done to determine the optimum LaB6 cathode tip shape and crystallographic orientation which will provide the highest brightness over cathode lifetime. The purpose of this is to review some of the previous results, present further data, and draw conclusions as to the optimum LaB6 cathode tip shape for high sustained brightness over cathode life. Nearly all commercially available LaB6 cathodes for electron microscopy employ an axially oriented LaB6 <100> crystal with a conical tip. Most are made with a full cone angle of 2α=90° (Figure 1). Some have a small radius, hemispherical point at the apex of the cone, while others simply have a small diameter truncation (flat) on top of the cone. The geometrical parameters affecting cathode brightness which will be considered here are hemispherical tip radius (R) and flat diameter (ϕ). Of primary interest is the dependence of brightness over lifetime with the variation of these parameters, and the comparison between the hemispherical and the flat tips.
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Roy, T., i R. Balasubramaniam. "Effect of various factors influencing the generation of hemispherical micro features using non-conformal RMEDM". Journal of Micromanufacturing 2, nr 2 (1.04.2019): 110–22. http://dx.doi.org/10.1177/2516598419829593.
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Non-conformal reverse micro electrical discharge machining (NC-RMEDM) is a variant of conventional RMEDM developed by the present authors wherein modification in the tool is carried out to generate different shapes of micro features. In this study, the effect of various factors like flat bottom and taper bottom hole, inversing the position of tool and workpiece and changing the hole depth have been experimentally investigated to determine the optimal combination required for generating hemispherical shaped micro features. It was found that hemispherical shaped micro feature can be generated by employing tapered bottom blind hole as tool. Buoyancy assisted machining (BAM) with traverse of workpiece (anode) downwards into the tool (cathode) and vice versa, i.e., buoyancy opposed machining (BOM) with traverse of tool downwards into the workpiece were carried out to study the generation of hemispherical micro feature based on inversion of electrode positions. Although both BAM and BOM generated hemispherical shaped feature, BAM is preferred due to reduced machining time as opposed to BOM. Also, increasing the hole depths led to altering the shape of micro feature from hemispherical to cylindrical with hemispherical end and coni-spherical end. An array of hemispherical micro features was fabricated based on the finding from this study, and surface roughness analysis was carried out which showed that irrespective of the position of micro feature on the array, surface roughness at the tip and base of the micro feature is lower as compared to side portion.
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Yao, Tao, Shu-Dao Zhou, Min Wang, Song Ye i Yang-Chun Zhang. "Optimal Design of Hemispherical 7-Hole Probe Tip With Perpendicular Holes". IEEE Access 9 (2021): 85101–8. http://dx.doi.org/10.1109/access.2021.3087613.
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Hollis, Brian R. "Correlation of Recent and Historical Hemispherical Nose Tip Distributed Roughness Transition Data". Journal of Spacecraft and Rockets 56, nr 3 (maj 2019): 664–86. http://dx.doi.org/10.2514/1.a34219.
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FASOULAS, J., i Z. DOULGERI. "ACTIVE CONTROL OF ROLLING MANOEUVRES OF A ROBOTIC FINGER WITH HEMISPHERICAL TIP". International Journal of Humanoid Robotics 07, nr 01 (marzec 2010): 183–212. http://dx.doi.org/10.1142/s0219843610002039.
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In this paper we are concerned with the problem of sensory motor coordination of a robotic finger in order to evoke rolling maneuvers in a force-positioning task on a flat rigid surface. We use two different approaches to modeling the reaction of the soft fingertip with the contacted surface. Firstly, we assume that the environment imposes a purely kinematic rolling constraint on the end-effector motion in the tangent direction of the contacted surface. This implies no energy transfer or dissipation between the fingertip and the environment due to frictional forces. On the other hand, we assume that it is feasible for the fingertip to slip in which case pure rolling motion could be disturbed. The two different models are subsequently used to show by simulation that control laws, which have been designed on a rolling constraint dynamic model for frictional forces, fail to perform rolling in various environments. An extra control input that uses a reference rolling trajectory that is state dependent is proposed, which, if superimposed on a conventional force-position control law, can achieve rolling even on a surface with low friction characteristics. The proposed feedback signal does not utilize the modeling information in the control formulation, and thus permits easy implementation. Finally, the total controller is shown to achieve asymptotic convergence to the desired force-positioning task by simultaneously evoking pure rolling motion for the fingertip.
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Wibowo, Edy, Sutisna, Naily Ulya i Mamat Rokhmat. "Spin Direction of a Hemispherical Object". Physics Teacher 61, nr 3 (marzec 2023): 222–23. http://dx.doi.org/10.1119/5.0048889.
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When rotating a ball using a hand [Figs. 1(a) and (b)], the fingers that touch the ball’s outer surface will exert frictional forces on the ball. These frictional forces cause torques on the ball so that the ball spins in the same direction as the finger’s rotational direction. If the finger rotates clockwise, the ball’s rotational direction will also be clockwise and vice versa. When the ball is cut into half, it is rotated similarly to when spinning a full ball. Thus, we can easily guess that its direction of rotation will be the same as when circling a full ball. What if the ball is spun differently? The half ball is spun using one fingertip from the bottom center of the inside, as shown in Figs. 1(c) and (d). What is the direction of rotation of the half ball? Would it be the same as when the ball is rotated from the outside? It turns out that the spin direction of the half ball is the opposite of the finger’s spin direction. The same result was observed when using a pen or a stick to rotate the half ball from the center base [Fig. 1(d) and supplemental video. Finally, suppose we shift the finger’s tip to any location so that it will no longer be at the center of the bottom of the object. In that case, the half ball’s rotation direction is similar to the one of the finger or stick. Why does this happen? In this paper, the answer to this question is presented.
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Ahmida, Mahmoud Abdelrazek, Mahmoud Abdelrazek Ahmida, Abdlmanam S. A. Elmaryami, Farag Gait Abelrahman Boukhrias i Ahmed M. Ahmed El Menshaz. "Investigation of Using Physical Optical Reflectivity Probes in Evaluating and Monitoring Powder Mixtures of Sugar and Slag". Instrumentation Mesure Métrologie 21, nr 2 (30.04.2022): 43–48. http://dx.doi.org/10.18280/i2m.210202.
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A preliminary investigation of some factors which can affect the reflected light intensity from granular and icing sugar has been carried out using an end viewing hemispherical tip probe. It is found that the reflectance is strongly dependent on the size range of the sugar particles, with the finer particles being more reflective. This property could be very useful in monitoring segregation in mixtures of mono-colored powders having different size distributions. Force applied to the probe will also affect the intensity readings. A layered mixture of sugar and slag powder was used to compare the sampling performance of the above probe with a side viewing wedge tip probe. Calibration curves for reflected light intensity versus percent slag concentration are obtained for two types of slag.
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DAVIES, KERRIE, ROBIN GIBLIN-DAVIS, WEIMIN YE, GARY TAYLOR i KELLEY THOMAS. "Nematodes from galls on Myrtaceae. III. Fergusobia from flower bud and stigma galls on Eucalyptus, with descriptions of four new species". Zootaxa 3532, nr 1 (31.10.2012): 1. http://dx.doi.org/10.11646/zootaxa.3532.1.1.
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Four new species of Fergusobia from flower bud galls and a stigma gall on Eucalyptus spp. in Australia are described. Fer-gusobia eugenioidae Davies n. sp. is characterised by having an arcuate, open C or C-shaped parthenogenetic female witha conoid tail, an arcuate to open C-shaped infective female with a hooked tail region and a broadly rounded tail tip, andarcuate or open C-shaped males with angular spicules and short bursa. Fergusobia fasciculosae Davies n. sp. is character-ised by the combination of an arcuate parthenogenetic female with a short, broadly conoid tail, an open C-shaped infectivefemale with a hemispherical tail tip, and J-shaped males with angular spicules and short peloderan bursa. This is the firstFergusobia/Fergusonina association to be described from flower stigma galls. Fergusobia juliae Davies n. sp. is character-ised by the combination of an arcuate to C-shaped parthenogenetic female with a short, broadly conoid tail, a J-shaped in-fective female with a hooked tail region, a cuticular plate around the vulva, and a broadly rounded tail tip, and J-shapedmales with angular spicules and short peloderan bursa. Fergusobia morrisae Davies n. sp. has a C-shaped parthenogeneticfemale with a narrowly conoid tail, an arcuate or J-shaped infective female with most curvature behind the vulva and a shorttail with an almost hemispherical tip, and arcuate or J-shaped males with strongly sclerotised, angular spicules and a longpeloderan bursa. Other known similar forms of Fergusobia/Fergusonina flower bud galls from Eucalyptus spp. are outlinedand the larval shield morphology of their associated mutualistic fly species is discussed where known. An inventory of allknown Fergusobia/Fergusonina associations from flower bud galls from Eucalyptus spp. is presented. Molecular analysisof Fergusobia nematodes was inferred from DNA sequencing of 28S rDNA D2/D3 domains and a portion of mitochondrial DNA cytochrome oxidase subunit I (mtCOI). Possible evolutionary relationships are discussed.
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Tembhurnikar, Payal, Akash Jadhav i Devabrata Sahoo. "Effect of intermediate aerodisk mounted sharp tip spike on the drag reduction over a hemispherical body at Mach 2.0". FME Transactions 48, nr 4 (2020): 779–86. http://dx.doi.org/10.5937/fme2004779t.
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Reduction of forebody drag in high speed flying vehicles such as rockets and missiles are of high research interest in the present time. In the present research, drag reduction obtained by using an intermediate aerodisk mounted sharp tip spike has been investigated using computational studies at Mach number of 2.0. The flowfield over a hemispherical blunt body with an intermediate aerodisk mounted sharp tip spike is investigated at zero degree angle of attack and the amount of drag reduction obtained is then compared with that of a conventional sharp tip spike mounted hemisphere. The presence of an intermediate aerodisk changes the flow physics and shock system over the blunt body. The change in the system of shock waves by mounting an intermediate aerodisk results in a higher percentage (20% higher) of drag reduction generated by the blunt spiked body moving at a supersonic speed of Mach 2.0. Use of intermediate aerodisk proves to be beneficial in terms of drag reduction for spike lengths ranging beyond the critical length.
Rozprawy doktorskie na temat "HEMISPHERICAL TIP"
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Mayberry, Curtis Lee. "Interface circuits for readout and control of a micro-hemispherical resonating gyroscope". Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53116.
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Gyroscopes are inertial sensors that measure the rate or angle of rotation. One of the most promising technologies for reaching a high-performance MEMS gyroscope has been development of the micro-hemispherical shell resonator. (μHSR) This thesis presents the electronic control and read-out interface that has been developed to turn the μHSR into a fully functional micro-hemispherical resonating gyroscope (μHRG) capable of measuring the rate of rotation. First, the μHSR was characterized, which both enabled the design of the interface and led to new insights into the linearity and feed-through characteristics of the μHSR. Then a detailed analysis of the rate mode interface including calculations and simulations was performed. This interface was then implemented on custom printed circuit boards for both the analog front-end and analog back-end, along with a custom on-board vacuum chamber and chassis to house the μHSR and interface electronics. Finally the performance of the rate mode gyroscope interface was characterized, showing a linear scale factor of 8.57 mv/deg/s, an angle random walk (ARW) of 34 deg/sqrt(hr) and a bias instability of 330 deg/hr.
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UPADHYAY, NEHA. "ROLE OF HETEROATOMS ON CYLINDRICAL CNT SURFACE WITH HEMISPHERICAL TIP". Thesis, 2016. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15150.
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This project puts forward a theoretical model to examine the growth of the carbon
nanotube (CNT) on top of catalyst substrate surface subjected to reactive plasma. Various
processes have been considered in this model, such as the charging rate of the CNT, kinetics of
electron, ions and neutral atoms. Also, the growth of the CNT due to diffusion and accumulation
of ions on the catalyst nanoparticles is taken into account. For characteristic glow discharge
plasma, numerical calculation on the impact of ion density, temperature and the substrate bias
over the growth rate of carbon nanotubes has been carried out. Through it, the change in radius,
height and the number density of hydrocarbon ions with time has been shown. Comparison has
been made between the two doped gases that are nitrogen and boron, and also with the undoped
condition. Along with it, the change in the concentration of the hydrocarbon ions in plasma along
the time is computed for three conditions (undoped, nitrogen doped and boron doped). The CNT
considered here has hemi-spherical tip as it provides better field emission which distinguish this
work from the work of Tewari and Sharma [31]. Different gases have been used in the process.
The mixture of gases includes hydrocarbon (CH3), hydrogen (H2), nitrogen (N2) and boron (B). It
is obtained that the height of CNT increments with the number density of carbon ions and radius
of CNT reduces with hydrogen ion density. The nitrogen and boron acts as doping elements here.
It is found that nitrogen obstruct both the height as well as radius of CNT, whereas in boron, both
the radius and height increases in comparison to the nitrogen doping. The present work can serve
to the better comprehension of procedure parameters amid growth of hemispherical tip CNT
with cylindrical surface by a Plasma Enhanced Chemical Vapor Deposition (PECVD) method.
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SHARMA, ANAND. "FIELD EMISSION OF ELECTRONS FROM HEMISPHERICAL CONDUCTING CARBON NANOTUBE TIP INCLUDING THE EFFECT OF IMAGE FORCE". Thesis, 2016. http://dspace.dtu.ac.in:8080/jspui/handle/repository/14632.
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ABSTRACT
The present work examines the field emission from Conducting Hemispherical Carbon Nanotune (CNT) tip including the Effect of Image Force. An expression for electrostatic potential for a Hemispherical CNT tip at a distance from the centre of CNT has been derived. Using the time-independent Schrodinger equation corresponding expressions for transmission coefficient and field emission current density have been derived for the Hemispherical Conducting Carbon Nanotubes. The numerical calculations of potential, transmission coefficient and the current density function have been calculated for a typical set of carbon nanotube parameters. From the expression of potential energy we found that the potential energy for the hemispherical CNT tip first increases and then decreases with the radial distance. The transmission coefficient increases with the normalized radial energy. And the current density function also increases with the normalized Fermi energy. An important outcome of the present work is that both transmission coefficient and field emission current density function decreases as the hemispherical CNT tip radius increases.
Książki na temat "HEMISPHERICAL TIP"
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Vallar, Giuseppe, i Nadia Bolognini. Unilateral Spatial Neglect. Redaktorzy Anna C. (Kia) Nobre i Sabine Kastner. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199675111.013.012.
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Left unilateral spatial neglect is the most frequent and disabling neuropsychological syndrome caused by lesions to the right hemisphere. Over 50% of right-brain-damaged patients show neglect, while right neglect after left-hemispheric damage is less frequent. Neglect patients are unable to orient towards the side contralateral to the lesion, to detect and report sensory events in that portion of space, as well as to explore it by motor action. Neglect is a multicomponent disorder, which may involve the contralesional side of the body or of extra-personal physical or imagined space, different sensory modalities, specific domains (e.g. ‘neglect dyslexia’), and worsen sensorimotor deficits. Neglect is due to higher-order unilateral deficits of spatial attention and representation, so that patients are not aware of contralesional events, which, however, undergo a substantial amount of unconscious processing up to the semantic level. Cross-modal sensory integration is also largely preserved. Neglect is primarily a spatially specific disorder of perceptual consciousness. The responsible lesions involve a network including the fronto-temporo-parietal cortex (particularly the posterior-inferior parietal lobe, at the temporo-parietal junction), their white matter connections, and some subcortical grey nuclei (thalamus, basal ganglia). Damage to primary sensory and motor regions is not associated to neglect. A variety of physiological lateralized and asymmetrical sensory stimulations (vestibular, optokinetic, prism adaptation, motor activation), and transcranial electrical and magnetic stimulations, may temporarily improve or worsen neglect. Different procedures have been successfully developed to rehabilitate neglect, using both ‘top down’ (training the voluntary orientation of attention) and ‘bottom up’ (the above-mentioned stimulations) approaches.
Części książek na temat "HEMISPHERICAL TIP"
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Maiti, Shubhendu, i Sankar Gangopadhyay. "A Simple but Accurate Method for Prediction of Reflected Intensity Noise for Single-Mode Circular Core Triangular Index Fiber Excitation via Upside Down Tapered Hemispherical Microlens on the Tip of Fiber". W Lecture Notes in Electrical Engineering, 53–62. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-9154-6_6.
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Altenmüller, Eckart, i Lauren Stewart. "Music supported therapy in neurorehabilitation". W Oxford Textbook of Neurorehabilitation, redaktorzy Volker Dietz, Nick S. Ward i Christopher Kennard, 421–32. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198824954.003.0031.
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Music-induced brain plasticity is a powerful means to improve neurologic function in rehabilitation following brain injury or degenerative disease. In motor dysfunctions following stroke, keyboard playing may improve fine motor functions along with neurophysiological changes in audiomotor networks. Rhythmic cueing has a positive effect in gait disorders, improving stride length, speed, and overall mobility. Melodic intonation therapy can improve recovery from non-fluent aphasia via activation of right-hemispheric networks. Music supported therapy can at least temporarily improve cognition in dementia and may have impact on rehabilitation of disorders of consciousness. Effects of music-induced brain plasticity together with music’s ability to tap into the emotion and reward system in the brain can thus be used to facilitate neurorehabilitation.
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Morís, Germán, i Julio Pascual. "Headache with neurological deficits and cerebrospinal fluid lymphocytosis (HaNDL) syndrome". W Oxford Textbook of Headache Syndromes, redaktorzy Michel Ferrari, Joost Haan, Andrew Charles, David W. Dodick, Fumihiko Sakai i Christopher Kennard, 403–8. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198724322.003.0044.
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Headache with neurological deficits and cerebrospinal fluid lymphocytosis (HaNDL) is a rare, self-limited syndrome that is characterized by 1–12 episodes of headache with temporary neurological deficits and cerebrospinal fluid lymphocytosis within a period of 3 months. HaNDL syndrome is more frequent in males (3:1) around their third and fourth decades of life. As HaNDL is commonly preceded by a viral illness, a possibility is that this syndrome is autoimmune in origin. Headache is usually described as severe and bilateral, and lasts from a few hours to a few days. Accompanying temporary deficits typically are restricted to one hemisphere and last an average of 5 hours. Sensory symptoms, language disorders, and hemiparesis, in this order, are the more frequent focal deficits. Contrary to migraine aura, visual symptoms are rare. While neuroimaging discloses no abnormalities, lumbar tap demonstrates lymphocytic pleocytosis with normal glucose levels and negative microbiological results. Electroencephalography and brain single photon emission computed tomography show hemispheric slowing or decrease uptake within the acute episodes. There is no specific treatment, but the syndrome does not leave any sequel.
Streszczenia konferencji na temat "HEMISPHERICAL TIP"
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Xie, Gongnan, Bengt Sunde´n i Quiwang Wang. "Predictions of Enhanced Heat Transfer of an Internal Blade Tip-Wall With Hemispherical Dimples or Protrusions". W ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22265.
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The blade tip region encounters high thermal loads because of the hot gas leakage flows, and it must therefore be cooled to ensure a long durability and safe operation. A common way to cool a blade tip is to design serpentine passages with 180-deg turn under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase the blade tip lifetime. Dimples and protrusions are well recognized as effective devices to augment heat transfer in various applications. In this paper, enhanced heat transfer of an internal blade tip-wall has been predicted numerically. The computational models consist of a two-pass channel with 180-deg turn and arrays of hemispherical dimples or protrusions internally mounted on the tip-wall. Inlet Reynolds numbers are in the range of 100,000 to 600,000. The computations are three dimensional, steady, incompressible and non-rotating. The overall performance of the two-pass channels is also evaluated. It is found that due to the combination of turning impingement and protrusion crossflow or dimple advection, the heat transfer coefficient of the augmented tip is a factor of 2.0 higher than that of a smooth tip. This augmentation is achieved at the cost of a penalty of pressure drop by around 5%. By comparing the present dimples or protrusions performance with others in previous works, it is found that the augmented-tips show the best performance, and the dimpled or protruded tips are superior to those pin-finned tips when the active area enhancement is excluded. It is suggested that dimples and protrusions can be used to enhance blade tip heat transfer and hence improve blade tip cooling.
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Crawford, James, i A. M. Birk. "Influence of Tip Shape on Reynolds Number Sensitivity for a Seven Hole Pressure Probe". W ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94382.
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The effects of tip shape on the Reynolds number sensitivity of a seven hole pressure probe are studied over a range of flows associated with practical use of turbomachinery. It is shown that at low flow angles, the response of a conical or hemispherical tipped probe is independent of Reynolds number above Re = 3000, and at high flow angles, Re = 6000. Despite there not being a discernable difference in the average error in flow properties at different Reynolds numbers between the two tip shapes, it is shown that the hemispherical tip is preferred because the pressure distributions around the tip are more consistent.
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Wang, Xiaochun, i Jinyang Zheng. "Safety Assessment of the Junction Between a Thick Pressure Vessel Shell and a Thinner Hemispherical Head". W ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1932.
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A junction of shell to hemispherical head whose thickness is half of that of the shell has been developed and safely used in the People’s Republic of China in the past ten years. Great achievements of mesomechanics in ductile fracture have been made in P. R. China. The load when local shear band prongs the ligament in the front of crack tip is regarded as the limit load and the direction of the maximum plastic strain along a constant radius around the crack tip might be considered as the direction of shear fracture. Based on these concepts and small-deformation elastic-plastic analysis with finite element method, safety of the junction under operating pressure, 31.4MPa, is assessed and the possible failure modes of it are forecasted. The reasonability of the design of the junction is also considered.
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Lavella, M., D. Botto i M. M. Gola. "Fretting Wear of CMSX4 at Blade Tip Interface With and Without Coating". W ASME/STLE 2009 International Joint Tribology Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/ijtc2009-15107.
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Fretting wear is a complex phenomenon that occurs at component interfaces that are subjected to low amplitude oscillation under high contact pressure. In turbomachinery fretting occurs also at the blade tip interfaces where shrouds, that have the aim to reduce the blade resonant vibration amplitude, are machined. To diminish the fretting damage coatings are applied to the blade tips. The aim of this study is to compare the fretting wear behaviour of single crystal CMSX-4 superalloy interfaces with and without plasma sprayed T-800 coating. Experiments have been conducted with hemispherical surface in contact with a flat surface of the same materials at temperature of 800 °C. The hysteresis cycles have been measured through the experiment. The comparison of the hysteresis cycles shown that the tangential contact stiffness of the coated surfaces is greater then that of the surfaces without coating. At the end of wear process, the mating surfaces have been characterized by three-dimensional optical interferometry and SEM analysis. After 10×106 wear cycles, the uncoated surfaces show a large change in the contact parameters and fretting cracks on the flat surface. On the other hand, the coated surfaces do not shows a measurable change in the contact parameters while the coating damage on the flat surface leads to predict an incipient catastrophic wear.
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Xie, Gongnan, Bengt Sunde´n i Weihong Zhang. "Comparisons of Pins/Dimples/Protrusions Cooling Concepts for a Turbine Blade Tip-Wall at High Reynolds Numbers". W 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22284.
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The blade tip region encounters high thermal loads because of the hot gas leakage flows, and it must therefore be cooled to ensure a long durability and safe operation. A common way to cool a blade tip is to design serpentine passages with 180° turn under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase blade tip lifetime. Pins, dimples and protrusions are well recognized as effective devices to augment heat transfer in various applications. In this paper, enhanced heat transfer of an internal blade tip-wall has been predicted numerically. The computational models consist of a two-pass channel with 180° turn and arrays of circular pins or hemispherical dimples or protrusions internally mounted on the tip-wall. Inlet Reynolds numbers are ranging from 100,000 to 600,000. The overall performance of the two-pass channels is evaluated. Numerical results show that the heat transfer enhancement of the pinned tip is up to a factor of 3.0 higher than that of a smooth tip while the dimpled-tip and protruded-tip provide about 2.0 times higher heat transfer. These augmentations are achieved at the cost of an increase of pressure drop by less than 10%. By comparing the present cooling concepts with pins, dimples and protrusions, it is shown that the pinned-tip exhibit best performance to improve the blade tip cooling. However, when disregarding the added active area and considering the added mechanical stress, it is suggested that the usage of dimples is more suitable to enhance blade tip cooling, especially at low Reynolds numbers.
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Gambarine, Dennis M., Felipe P. Figueiredo, André L. C. Fujarra i Rodolfo T. Gonçalves. "Experimental Study About the Influence of the Free End Effects on Vortex-Induced Vibration of Floating Cylinder With Low Aspect of Ratio". W ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54632.
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Experiments regarding free-end effects on vortex-induced vibration (VIV) of floating circular cylinders with low aspect ratio were carried out in a towing tank. Four cylinders with low aspect of ratio, L/D = 2 (Length / Diameter) were tested with different free end corner shape types, namely by the relation between chamfer rounding radius (r) divided by the radius of cylinder (R) (r/R = 0.0, 0.25, 0.5 and 1.0). For the initial case, r/R = 0.0 represents flat tip and r/R = 1.0 the hemispherical tip. The aims were to understand the effect of different free-end types on VIV behavior of cylinders. The floating circular cylinders, i.e. unit mass ratio m* = 1(structural mass/displaced fluid mass) were elastically supported by a set of linear springs to provide low structural damping on the system and allow six degrees of freedom. The range of Reynolds number covered 3,000 ≤ Re ≤ 20,000. To conclude, cylinder with r/R = 0.25, shows lower amplitudes in transverse direction. The same occurs for the cylinder r/R = 0, but for amplitudes of vibration in in-line direction. Behaviors of the vibration frequencies in in-line and transverse direction don’t have significantly differences. Regarding force coefficient, flat tip cylinder (r/R = 0) presents higher values compared to the others however, for the lift coefficient, results converge in similar values for the same velocities that were observed higher transverse amplitudes. The visualization experiments show an expressive reduction of the recirculation bubble for r/R = 0.5 model compared with the flat tip, can therefore justify the lower values for this model obtained in draft amplitudes and drag coefficient compared with the flat tip model.
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Prakash, Raghu V., i Deepika Sudevan. "Post-Impact Thermo-Mechanical Response of Woven Mat Composites Subjected to Tensile Loading". W ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66343.
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The thermo-mechanical response of carbon fiber reinforced polymer (CFRP) laminates subjected to continuous tensile loading and programmed interrupted tensile loading is examined to understand the changes due to damage progression. Quasi-isotropic laminates were prepared using 500 GSM twill weave carbon fabric with LY 556 resin and HY 991 hardener by hand lay-up technique, followed by curing under hot compression. A few specimens were subjected to an impact loading to 23 J and 51 J energy levels using a hemispherical tip to induce low velocity impact damage. Passive thermal imaging of woven CFRP laminates during tensile testing was captured using a TIM 160 Micro-epsilon infrared thermal camera. Temperature response during tensile testing provided a good correlation with deformation mode esp. for specimens impacted with 51 J of energy. Tensile tests were interrupted at periodic loads and unloaded and reloaded to study the thermal response after prior plastic deformation damage in the specimen. Unlike the case of GFRP specimens, distinct changes in thermo-elastic slope due to prior plastic deformation damage could not be clearly identified. As impact damage resulted in de-lamination of some layers, active thermography technique was used to study the rate of cooling of specimen with time when the damage is closer to the camera face as well as when it is away from the camera face. The cooling curves obtained were found to be dependent on the location of the damage, as well as on heating face of the specimen.
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Patel, Pragati, Abhijeet C. Gaonkar i Ayyappan M. "Novel Wideband Bow Tie shaped Hemispherical Dielectric Resonator Antenna". W 2022 National Conference on Communications (NCC). IEEE, 2022. http://dx.doi.org/10.1109/ncc55593.2022.9806475.
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Chon, James W. M. "Analytical formulation for field enhancement of gold bipyramids and hemispherically capped cylinders for application in two-photon luminescence and scattering". W JSAP-OSA Joint Symposia. Washington, D.C.: Optica Publishing Group, 2017. http://dx.doi.org/10.1364/jsap.2017.8a_a409_5.
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Recent advances in two-photon excited photoluminescence of plasmonic gold nanorods have greatly expanded their application. Shape-controlling of nanorods can enhance a particular photophysical process to tailor needs but its application to two-photon luminescence is yet to be fully developed despite its importance in biolabelling. In particular, bipyramidal gold nanorods have received a large amount of interest as a biolabelling due to highly localised field at their tips, which provide enhancement for emission processes. However, no proper evaluation of geometrical properties of bipyramids such as tip shape, curvature, pentagonal cross section or the waist have been conducted on the field enhancement and peak evolution. Numerical simulations using finite element analysis show that small change in tip radius of curvature can change nonlinear process such as two-photon luminescence (TPL) two to four-fold increase. However, such large increase is not observed in experimental measurement of TPL with respect to tip curvature, indicating that there is fundamental limit to how the field enhancement can influence emission processes.
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Jialin Liu, Qiulin Huang i Xiaowei Shi. "A bow-tie antenna on the extended hemispherical lens for THz frequency". W 2016 IEEE International Conference on Microwave and Millimeter Wave Technology (ICMMT). IEEE, 2016. http://dx.doi.org/10.1109/icmmt.2016.7762413.
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