ELECTRIC FLOW ACROSS A CIRCULAR SPOT BETWEEN PARALLEL PLATES

A mathematical treatment of the general problem of electrical contacts and heating related to MEMS switch contacts is developed. The spatial distri­ bution of the potential, the current and the temperature in a special case of electrical contact between two gold bodies whose thermal and electrical conductivities vary with temperature is analyzed, and an explanation for the collapse of gold contact system before reaching the melting point is given. For this purpose three different methods are applied. First, we develop an exact solution, which involves with solving a dual integral equation leading to a Fred­ holm integral equation, that is solved numerically. Secondly, a simple model to obtain an approximate resistance of an a-spot system is presented. Finally, another approximate solution is developed, where the variational method is implemented to reduce the complicated computations of the exact method. Excellent agreement is demonstrated between the results of the exact and the variational methods for all sizes of a-spots in contact systems

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

Erosion and Roughness Modeling in Abrasive Jet Micro-machining of Brittle Materials

The effect of particle size, velocity, and angle of attack was investigated on the roughness and erosion rate of unmasked channels machined in borosilicate glass using abrasive jet micro-machining (AJM). Single impact experiments were conducted to quantify the damage due to the individual alumina particles. Based on these observations, an analytical model from the literature was modified and used to predict the roughness and erosion rate. A numerical model was then developed to simulate the brittle erosion process leading to the creation of unmasked channels as a function of particle size, velocity, dose, impact angle and target material properties. For the first time, erosion was simulated using models of two damage mechanisms: crater removal due to the formation and growth of lateral cracks, and edge chipping. Accuracy was further enhanced by simulating the actual relationship between particle size, velocity and radial location within the jet using distributions measured with high-speed laser shadowgraphy. The process of post-blasting AJM channels with abrasive particles at a relatively low kinetic energy was also investigated in the present work by measuring the roughness reduction of a reference unmasked channel in borosilicate glass as a function of post-blasting particle size, velocity, dose, and impact angle. The numerical model was modified and used to simulate the post-blasting process leading to the creation of smooth channels as a function of particle size, velocity, dose, impact angle, and target material properties. Finally, the effect of alumina particle kinetic energy and jet impact angle on the roughness and erosion rate of channels machined in borosilicate glass using abrasive slurry jet micro-machining (ASJM) was investigated. The analytical and numerical models derived for AJM, were found to predict reasonably well the roughness and the erosion rate of ASJM channels, despite the large differences in the fluid media, flow patterns, and particle trajectories in AJM and ASJM.Ph

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

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