Part Of Hemisphere Research Articles

A generalized spherical harmonics-based procedure for the interpolation of partial datasets of orientation distributions to enable crystal mechanics-based simulations

Microstructure evolution-based constitutive models in macro-scale simulation tools require statistical microstructure input at each integration point. This paper reports several robust procedures for interpolating orientation distribution functions (ODFs) from coarsely spaced experimental measurement grids to finely spaced modeling grids. The procedures are based on representing ODFs using generalized spherical harmonics (GSH) functions. Relying on the linearity of the expansion space, the core of the procedures involves weighting of the GSH expansion coefficients over a given variable such as space, strain, or temperature, thus providing ODFs as a function of location, deformation, or thermal treatment. Interpolation approaches including regression and linear/bilinear/barycentric weighting are explored and discussed in terms of their accuracy and suitability. Upon establishing the expansion coefficients of the interpolated ODF, a linear programing problem is solved within the expansion space to construct the interpolated ODF. The procedures are applied to a comprehensive data set obtained by neutron diffraction for a hemispherical part made of depleted α-uranium. Utilizing the ODF interpolation procedures, texture is interpolated over the part revealing significant anisotropy in the texture dependent thermal expansion and elastic stiffness coefficients. The results of this work facilitate introducing thermal expansion and elastic anisotropy into numerical tools for simulating thermo-mechanical loading of microstructurally heterogeneous components using the ODF informed crystal mechanics-based models to more accurately estimate the effective properties required by such simulations.

Research of the explosive formation of a compact element for meteoroids fragments and space debris modelling

X-ray research of particles formed during the explosion of a shaped charge with steel liner of the combined hemisphere-cylinder shape with a jet-forming part of a degressive (decreasing from top to base) thickness and a cylindrical part is carried out. It was experimentally confirmed that the transition from the constant to the degressive thickness of the hemispherical part of the liners allows to increase the velosity of the head section of the material formed during its compression by the jet flow of the material, which is cut off during the collapse of the cylindrical part of the liner. The velosity of a steel compact non-gradient element recorded in experiments for tested variants of a shaped charge was 7.8 … 8.6 km/s, which, within the permissible experimental errors, corresponds to the results of previously performed numerical calculations and approximately 30% higher than the speed of the corresponding element obtained using constant thickness.

Genetic diversity and geographic distribution of Bemisia tabaci and Trialeurodes vaporariorum in Costa Rica

The tobacco whitefly Bemisia tabaci (Gennadius) cryptic species complex and of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) are extensively reported as destructive pests in vegetable crops worldwide. A survey was conducted in 2011 and 2012 to determine the occurrence and genetic diversity present in the populations of these whiteflies in the major vegetable production areas of Costa Rica. Insect samples were collected from sweet pepper (Capsicum annuum L.), tomato (Solanum lycopersicum L.), common bean (Phaseolus vulgaris L.) and weeds present in commercial crops either in open field or greenhouse conditions. PCR‐RFLP analysis of mitochondrial cytochrome c oxidase subunit 1 gene (mtCOI) sequences of 621 whitefly individuals confirmed the presence of the Mediterranean (MED) type of the B. tabaci and of T. vaporariorum in most sampled regions. Also, individuals of the Middle East‐Asia Minor 1 (MEAM1) type of the B. tabaci were observed in low numbers. Contingency analyses based on type of crop, geographical region, whitefly species, year of collection and production system confirmed that T. vaporariorum was the most frequent species in vegetable production areas in Costa Rica, both in greenhouses and in open fields. B. tabaci MED is likely spreading to new areas of the country, whereas B. tabaci MEAM1 was mostly absent or rarely found. Comparisons of mtCOI sequences from B. tabaci individuals revealed the presence of four B. tabaci sequence haplotypes (named MED‐i, MED‐ii, MEAM1‐i, MEAM1‐xviii) in Costa Rica, three of them identical to B. tabaci haplotypes previously reported in the Western Hemisphere and other parts of the world. Analysis of sequences of T. vaporariorum individuals revealed a more complex population with the presence of 11 haplotypes, two of which were identical to T. vaporariorum sequences reported from other countries.

Brain abscess potentially secondary to periodontal infection resulting in death of a young patient

AbstractThis study aimed to report a case of a 17‐year‐old female patient referred to the oral and maxillofacial surgery (OMS) team from Santa Casa de Araçatuba who was unconscious, had a Glasgow coma score of 3, and was diagnosed by a neurosurgeon with brain death. Her mother reported that the patient showed no systemic disease. The patient underwent a supragingival curettage after completion of an orthodontic treatment. One day after the procedure, the patient showed oedema at the canine superior right space and fluctuation point. After the abscess was drained, there was a worsening of clinical condition. The patient was referred to the Intensive Care Unit and showed only a leukocytosis (approximately 17 000 mm³). The OMS team observed a tissue necrosis on her right superior lip extending to the lower eyelid on the same side and oedema of the periorbital region. On computed tomography sections, hypodense images affecting the larger part of the right cerebral hemisphere were observed, suggestive of brain abscess. Unfortunately, the patient showed no response and her condition evolved to brain death, as diagnosed by electroencephalogram tests performed three times every 12 h. It is necessary to be highly careful with even minimal signs of infection, because we never know the aggressiveness of the bacteremia.

Numerical study of supersonic flow over axisymmetric bodies with combined supply of energy into incoming undisturbedflow

The development of supersonic aircrafts should rely on advanced methods of flow control in order to improve the efficiency and reliability of the aircrafts. This article presents numerical simulation of energy supply to the incoming flow and simulation of the flow over bodies with hemispherical and conical nose parts. The numerical study was based on the model of an inviscid perfect gas described by the Euler equations which were solved by using the explicit unsteady Godunov’s numerical scheme with the second-order accuracy.

Patterns of Cerebellar Gray Matter Atrophy Across Alzheimer's Disease Progression.

The role of the cerebellum in cognitive function has been broadly investigated in the last decades from an anatomical, clinical, and functional point of view and new evidence points toward a significant contribution of the posterior lobes of the cerebellum in cognition in Alzheimer’s disease (AD). In the present work we used SUIT-VBM (spatially unbiased infratentorial template, voxel-based morphometry) to perform an analysis of the pattern of cerebellar gray matter (GM) atrophy in amnestic mild cognitive impairment (a-MCI) and AD dementia patients compared to healthy subjects (HS), in order to follow the changes of non-motor features of cerebellar degeneration throughout disease progression. This template has been validated to guarantee a significant improvement in voxel-to-voxel alignment of the individual fissures and the deep cerebellar nuclei compared to Montreal Neurological Institute (MNI) whole-brain template. Our analysis shows a progression of cerebellar GM volume changes throughout a continuous spectrum from early to late clinical stages of AD. In particular vermis and paravermian areas of the anterior (I-V) and posterior (VI) lobes are involved since the a-MCI stage, with a later involvement of the hemispheric part of the posterior lobes (VI lobule) and Crus I in AD dementia patients only. These findings support the role of the cerebellum in higher-level functions, and whilst confirming previous data on the involvement of Crus I in AD dementia, provide new evidence of an involvement of the vermis in the early stages of the disease.

Forming of hemispherical and hemi-ellipsoidal parts of low carbon steel sheet by mandrel free metal spinning process

Metal spinning (MS) is an efficient and economical alternative method for low-volume functional sheet metal products. It has higher potential to shape three dimensional parts without employing matching die. The focus in advancement of shape forming shall bring an effective approach to produce defect free shapes and economically viable products. This paper is going to discuss about the modification in the MS process, without using matching dies or mandrel to produce a hemispherical and hemi-ellipsoidal profile product. The forming occurs by the deformation of sheet metal when the roller feed is against the rotating metal blank. Low carbon extra deep drawing Al killed steel sheets of thickness 1.6 mm were exploited as forming material. Further the paper illustrates on thickness variation, hardness, micro-structure, surface roughness and forming limit diagram (FLD) of the various zone of the formed part. It is examined that as the depth varies, the changes in thickness of formed part also varies. Also, the surface roughness was proportionally increased with increasing in percentage of reduction in thickness. In all zone of the formed steel part are in tension- tension strain conditions, there is no tension compression and plane strain condition occurred in the forming process. Due to this reason wrinkles failure is eliminated in die less MS process.

Endoreplication and its consequences in the suspensor of Pisum sativum

Key messageDNA replication and continuous process of transcription during ongoing amitotic division accelerate the development of four-celled pea suspensor containing nuclei which create transient gradient of polyploidy necessary for correct embryo development.A suspensor, the link between embryo proper and surrounding tissues, differs significantly in size, morphology, and degree of polyploidy among the species. The suspensor of Pisum sativum consists of four polynuclear cells (two hemispherical and two elongated) formed in two layers. Their nuclei undergo endoreplication reaching, respectively, up to 256C and 128–256C DNA levels in its hemispherical and elongated parts. Our study shows that endoreplication first appears in the spherical part of the suspensor, and, subsequently, in the elongated one. At the next stages of suspensor development, the increase in DNA content takes place also in a similar order. Thus, despite simple construction of the suspensor, its development, supported by endoreplication, creates a certain gradient of polyploidy, which occurs in more extensive suspensors. Moreover, the rapid development of suspensor is supported both by the initiation of DNA replication prior to the completion of amitotic division of its polyploidal nuclei and by a continuous process of transcription, which is silenced by chromatin condensation throughout mitosis. Furthermore, the increase in DNA content correlates with the greater amount of transcripts; however, the multiplication of DNA copies does not entail an increase (but fluctuation) in the mean transcriptional activity of a particular nucleus during the next stages of suspensor development.

Clinical and electrographic presentation of a case of hemimegalencephaly

Objectives Epilepsy is a common and potentially serious and disabling disease. Congenital malformations of the brain are often associated with severe presentations and difficult drug control. Our objective is to report a case of a child with hemimegalencephaly, the clinical and electroencephalographic presentation before and after neurosurgery. Methods RAR, a 2-year-old girl with difficult-to-control epilepsy using a combination of high doses of anticonvulsants, presented daily crisis from the neonatal period. She was monitored with video-EEG before and after brain surgery. Clinical presentation and electroencephalographic changes helped to indicate the procedure. Results The video-EEG showed crises characterized by behavioral arrest, eyes up and stillness. Inter-ictal EEG had continuous poly-spykes in the right hemisphere and focal EEG accentuates epileptiform activity over the right quadrant region. Magnetic resonance imaging of the requested brain with right hemimegalencephaly. The patient underwent right hemispherectomy in December 2017, provided no recurrence of crisis. Her behavior and development is also better. She will be admitted shortly for a new video-EEG monitoring. Conclusion Hemimegalencephaly is a malformation of cortical development characterized by excessive hamartomatous growth of all or part of a cerebral hemisphere and frequently associated with refractory epilepsy. Patients may present with early encephalopathy, delayed neuropsychomotor development, motor deficits and learning disabilities. Anatomic or functional hemispherectomy is indicated if epilepsy is clinically intractable.

Effects of backward path parameters on formability in conventional spinning of aluminum hemispherical parts

Abstract During multi-pass conventional spinning, roller paths combined with the forward and the backward pass are usually used to improve the material formability. In order to understand the backward spinning process properly, the backward roller paths of hemispherical parts with aluminum alloy 2024-O are analyzed. Finite element model with parameterized conventional spinning roller paths, which are based on quadratic Bezier curves, is developed to explore the evolution of the stress, strain and thinning during the backward processes. Analysis of the simulation results reveals stress and strain features of backward pass spinning. According to the findings, the application of the backward pass can obviously improve the uniformity of wall thickness. Furthermore, references of the parameters in future backward path design are provided.

A search for temporal changes on Pluto and Charon

A search for temporal changes on Pluto and Charon was motivated by (1) the discovery of young surfaces in the Pluto system that imply ongoing or recent geologic activity, (2) the detection of active plumes on Triton during the Voyager 2 flyby, and (3) the abundant and detailed information that observing geologic processes in action provides about the processes. A thorough search for temporal changes using New Horizons images was completed. Images that covered the same region were blinked and manually inspected for any differences in appearance. The search included full-disk images such that all illuminated regions of both bodies were investigated and higher resolution images such that parts of the encounter hemispheres were investigated at finer spatial scales. Changes of appearance between different images were observed but in all cases were attributed to variability of the imaging parameters (especially geometry) or artifacts. No differences of appearance that are strongly indicative of a temporal change were found on the surface or in the atmosphere of either Pluto or Charon. Limits on temporal changes as a function of spatial scale and temporal interval during the New Horizons encounter are determined. The longest time interval constraint is one Pluto/Charon rotation period (∼6.4 Earth days). Contrast reversal and high-phase bright features that change in appearance with solar phase angle are identified. The change of appearance of these features is most likely due to the change in phase angle rather than a temporal change. Had active plumes analogous to the plumes discovered on Triton been present on the encounter hemispheres of either Pluto or Charon, they would have been detected. The absence of active plumes may be due to temporal variability (i.e., plumes do occur but none were active on the encounter hemispheres during the epoch of the New Horizons encounter) or because plumes do not occur. Several dark streak features that may be deposits from past plumes are identified.

Oculomotor Disturbances in Patients with Chronic Nonspecific Spinal Pain.

There is increasing evidence that the cerebellum has a role in pain processing. The present study investigates whether chronic pain patients, who are likely to have altered pain processing, exhibit signs of subtle cerebellar dysfunction. We used oculomotor tasks to assess dysfunction of the associated neuronal networks, including the cerebellum. Thirty patients with chronic nonspecific spinal pain and 30 age- and sex-matched controls were enrolled. Using a head-mounted eye tracker (EyeSeeCam), eye movements were quantified during predictable and unpredictable saccade and smooth pursuit tasks in the horizontal plane. The initial latency and the velocity variability of smooth pursuit were significantly increased in the chronic spinal pain patients compared with controls (initial latency: 198 ± 20 vs 185 ± 11 ms, P < 0.01; slow phase velocity standard deviation: 3.31 ± 1.02 vs 2.70 ± 0.83°/s, P < 0.05). Moreover, the latency of predictable saccades was prolonged in patients (rightward: 161 ± 20 vs 152 ± 12 ms, P < 0.05; leftward: 164 ± 22 vs 153 ± 18 ms, P = 0.05). Our results show that chronic spinal pain patients display subtle but significant oculomotor changes as compared with healthy controls. Considering the networks involved in the generation of saccades and smooth pursuit, the results would be consistent with a dysfunction of cerebellar regions, especially parts of the cerebellar hemispheres. Alternatively, they could also point toward a dysfunction in the frontal eye field and/or pontine oculomotor nuclei.

Neurological complications associated with chronic Behçet’s disease: Case report and review

Behçet’s disease is a multi-systemic vasculitis causing inflammation to blood vessels throughout the body. It is characterized most commonly by recurrent oral and genital ulcers but also susceptible to ocular, neurologic, vascular, articular, and gastrointestinal symptoms as well. Although etiology of this disease is still unclear and diagnosis is clinically based, there is a consistent association with the human leukocyte antigen complex, particularly HLA-B51.This case report used the patient’s chronic disease course along with various imaging studies to conclude the correlation of severe complications that may present later in life of these types of patients.There was positive neurological involvement indicated with an acute infarct in parts of the brain hemispheres exclusively to the temporal and parietal lobes. Central nervous system involvement was more common in this patient, which manifested with noticeable unilateral weakness along with slurred speech.Although neurologic complications within Behçet’s disease are indeed rare, it is one of the most dangerous manifestations to present in regard of an acute cerebrovascular accident (CVA). This review focused on the neurocognitive complications of chronic Behçet’s disease and how these patients should be closely monitored to help prevent the neurological complications that may present.

FMRI Visualization of Functional Patterns of Neural Networks during the Performance of Cyclic Finger Movements: Age-Related Peculiarities

Using functional magnetic resonance imaging (fMRI), we visualized patterns of activity of neural macronetworks in healthy humans during the performance of cyclic finger movements and studied agerelated peculiarities of these patterns. Three age groups of subjects (7 to 86 years old) were examined. The paradigm of activation corresponded to simple repeated test movements of touching of the fingerpads of the forefinger and thumb of the right hand. We analyzed patterns of activation, deactivation, and functional connectivity of the brain sensorimotor, default, and frontoparietal networks. Schemes of activation of zones of the primary and associative sensorimotor cortex related to the test task performance by subjects of different ages were rather similar to each other. Concurrently with the processes of activation of the sensorimotor network, we observed partial deactivation of certain nodi of the default mode network and formation of functional connectivity between some such nodi. The obtained data confirm the statement that the default mode network is heterogeneous; different parts of this network can simultaneously demonstrate desynchronization and autonomic functioning. There are reasons to believe that, in the junior age, the functional connectivity of zones corresponding to the default mode network had been formed incompletely. We found the functional connectivity of the frontoparietal neural network consisting of parts of the parietal cortex and dorsolateral prefrontal cortices of both cerebral hemispheres. In elderly subjects, the functional connectivity between the dorsolateral prefrontal cortex of the left hemisphere and other parts of the frontoparietal neural network is weakened.

Determination of Process Parameters in Multi-Stage Hydro-Mechanical Deep Drawing by FE Simulation

In this work, analysis has been carried to simulate manufacturing of a near hemispherical bottom part with large depth by hydro-mechanical deep drawing with an aim to reduce the number of forming steps and to reduce the extent of thinning in the dome region. Inconel 718 has been considered as the material due to its importance in aerospace industry. It is a Ni-based super alloy and it is one of the most widely used of all super alloys primarily due to large-scale applications in aircraft engines. Using Finite Element Method (FEM), numerical simulations have been carried out for multi-stage hydro-mechanical deep drawing by using the same draw ratios and design parameters as in the case of conventional deep drawing in four stages. The results showed that the minimum thickness in the final part can be increased significantly when compared to conventional deep drawing. It has been found that the part could be deep drawn to the desired height (after trimming at the final stage) without any severe wrinkling. Blank holding force (BHF) and peak counter pressure have been found to have a strong influence on thinning in the component. Decreasing the coefficient of friction has marginally increased the minimum thickness in the final component. By increasing the draw ratio and optimizing BHF, counter pressure and die corner radius in the simulations, it has been found that it is possible to draw the final part in three stages. It has been found that thinning can be further reduced by decreasing the initial blank size without any reduction in the final height. This reduced the draw ratio at every stage and optimum combination of BHF and counter pressure have been found for the 3-stage process also.

A study of severe flange wrinkling in first-pass conventional spinning of hemispherical part

Flange wrinkling is one of the most common defects in conventional spinning. Slight wrinkles can be eliminated by a reasonable design of the spinning process parameters or assisted process, while severe wrinkles lead to low forming quality or even defective products. A lot of work has been done to find the reason for flange wrinkling and the way to avoid it, while limited research has been done to study the severe flange wrinkling phenomenon in conventional spinning process. In this paper, the severe flange wrinkling phenomenon in first-pass conventional spinning of the hemispherical part has been studied through FE (finite element) simulations and experiments. A double curved surface buckling prediction model based on the energy method is proposed in order to predict severe flange wrinkling. Experiments are designed to verify the theoretical severe flange wrinkling prediction method. It turns out that the wrinkling of the inner compressive stress ring leads to the severe fluctuations of the spinning force, and it can be taken as a sign of severe flange wrinkling in the conventional spinning process. Furthermore, the effects of flange wrinkling on the spinning qualities of the final formed hemispherical parts are researched. It is concluded that slight flange wrinkles in the first-pass have little effects on thickness distribution and geometry accuracy of the final formed part, while severe flange wrinkles lead to failed products. Severe flange wrinkling prediction is significant for the conventional spinning of the hemispherical part.

Investigation into the Fiber Orientation Effect on the Formability of GLARE Materials in the Stamp Forming Process

Glass-reinforced aluminum laminate (GLARE) is a new class of fiber metal laminates (FMLs) which has the advantages such as high tensile strength, outstanding fatigue, impact resistance, and excellent corrosion properties. GLARE has been extensively applied in advanced aerospace and automobile industries. However, the deformation behavior of the glass fiber during forming must be studied to the benefits of the good-quality part we form. In this research, we focus on the effect of fiber layer orientation on the GLARE laminate formability in stamp forming process. Experimental and numerical analysis of stamping a hemisphere part in different fiber orientation is investigated. The results indicate that unidirectional and multi-directional fiber in the middle layer make a significant effect on the thinning and also surface forming quality of the three layer sheet. Furthermore, the stress-strain distribution of the aluminum alloy and the unique anisotropic property of the fiber layer exhibit that fiber layer orientation can also affect the forming depths as well as the fracture modes of the laminate. According to the obtained results, it is revealed that multi-directional fiber layers are a good alternative compared to the unidirectional fibers especially when a better formability is the purpose.

Formation of a high-velocity particle flow from shaped charges with a liner consisting of a hemisphere and a degressive-thickness cylinder

Particle flows formed from shaped charges with a combined steel liner consisting of a hemisphere and a cylinder with a hemispherical part of degressive thickness (decreasing from top to bottom) were investigated by flash radiography. It has been found experimentally that the change from a constant to a degressive thickness of the hemispherical part increases the velocity of the head part of the liner jet formed during its compression, which is subsequently separated upon collapse of the cylindrical part. The maximum particle velocity obtained as a result of separation in the experiments was 8.6 km/s.

Optimisation of multi-point forming process parameters

The need for sheet metal forming using reconfigurable dies has increased due to rapid changes in part design to meet customer requirements, especially in the automotive industry. Reconfigurable dies have relatively low manufacturing cost compared with solid dies, and the same tool can be readily changed to produce different parts. Previous investigations have focused on avoiding defects without taking into account the effects of process on the quality characteristics of fabricated parts. This study investigated the influence of parameters, such as the elastic cushion thickness, coefficient of friction, pin size and radius of curvature, on the quality of parts formed in a flexible multi-point stamping die. The aim was to determine the optimum values of those parameters. Finite element modelling was employed to simulate the multi-point forming of hemispherical parts. Using the response surface method, the effects of process parameters on wrinkling, deviation from the target shape and thickness variation were investigated and the process parameters yielding the best product quality characteristics were obtained. The results show that pin size and radius of curvature have the greatest influence on wrinkling and deviation between formed and target shapes, while coefficient of friction, pin size and radius of curvature significantly affect thickness variation.

Thickness control in a new flexible hybrid incremental sheet forming process

Incremental sheet forming is a cost-effective process for rapid manufacturing of sheet metal products. However, incremental sheet forming also has some limitations such as severe sheet thinning and long processing time. These limitations hamper the forming part quality and production efficiency, thus restricting the incremental sheet forming application in industrial practice. To overcome the problem of sheet thinning, a variety of processes, such as multi-step incremental sheet forming, have been proposed to improve the material flow and thickness distribution. In this work, a new process has been developed by introducing multi-point forming as preforming step before conducting incremental sheet forming processing. Employing an established hybrid sheet forming system and the corresponding thickness prediction model, the preform shape can be optimized by employing a two-step optimization approach to improve the sheet thickness distribution. In total, two case study examples, including a hemisphere part and an aerospace cowling part, are fabricated using the developed hybrid flexible process in this study. The experimental results show that the hybrid flexible forming process with the optimal preform design could achieve sheet parts with more uniform thickness distribution and reduced forming time.