On combining chaos search and levenberg-marquardt algorithm for non-linear substituted geometric fitting problems

Product quality is becoming a main concern in today manufacturing. As such, dimensional metrology is strictly necessary. High accuracy result while reducing speed in measuring a product has to catch up with the improvement of metrology instrument which can capture many points in less time. Fitting algorithm of point clouds plays a critical role for the measurement accuracy and speed. In this study, non-linear least-square fitting of circle, sphere and cylinder without any prior knowledge of their nominal is addressed. These geometries have common use in practice, such as sphere for calibration and hole-shaft features in mechanical assembly application. The improvement of initial point guess for Levenberg-Marquardt (LM) algorithm by employing Chaos Optimization (CO) method is presented. The results show that, with this combination, higher quality of fitting results in term of smaller norm of the residuals can be obtained while preserving the computational cost

Three-dimensional resonating metamaterials for low-frequency vibration attenuation

Recent advances in additive manufacturing have enabled fabrication of phononic crystals and metamaterials which exhibit spectral gaps, or stopbands, in which the propagation of elastic waves is prohibited by Bragg scattering or local resonance effects. Due to the high level of design freedom available to additive manufacturing, the propagation properties of the elastic waves in metamaterials are tunable through design of the periodic cell. In this paper, we outline a new design approach for metamaterials incorporating internal resonators, and provide numerical and experimental evidence that the stopband exists over the irreducible Brillouin zone of the unit cell of the metamaterial (i.e. is a three-dimensional stopband). The targeted stopband covers a much lower frequency range than what can be realised through Bragg scattering alone. Metamaterials have the ability to provide (a) lower frequency stopbands than Bragg-type phononic crystals within the same design volume, and/or (b) comparable stopband frequencies with reduced unit cell dimensions. We also demonstrate that the stopband frequency range of the metamaterial can be tuned through modification of the metamaterial design. Applications for such metamaterials include aerospace and transport components, as well as precision engineering components such as vibration-suppressing platforms, supports for rotary components, machine tool mounts and metrology frames

Analisis Usaha Pemberian Bakteri Asam Laktat (BAL) pada Ayam Pedaging terhadap Persentase Berat Karkas

Peternakan merupakan subsektor pertanian yang memiliki peran penting dalam pemenuhan kebutuhan protein hewani yang semakin meningkat. Bakteri, virus, parasit, jamur, lingkungan dan kekurangan nutrisi merupakan penyebab rentannya peternakan ayam pedaging terserang penyakit. Penggunaan antibiotik merupakan salah satu cara pengobatan dan pencegahan penyakit, namun pemberian antibiotik yang tidak tepat dosis dapat menimbulkan residu antibiotik. Tujuan penelitian ini adalah untuk mengetahui analisis usaha ayam pedaging yang diberi bakteri asam laktat terhadap peningkatan persentase berat karkas. Terdiri dari 300 ekor DOC yang diacak kedalam tiga kelompok perlakuan, masing-masing terdiri dari 100 ekor. Perlakuan terdiri dari P0 (Pakan komersial dan air minum), P1 (Pakan komersial dan air minum + BAL 106 CFU/ml), dan P3 (pakan komersial dan air minum + BAL 108 CFU/ml). Hasil penelitian menunjukkan bahwa pemberian BAL pada air minum belum mampu meningkatkan persentase berat karkas dan menurunkan persentase lemak abdominal, namun layak untuk dilakukan karena masih memberikan keuntungan.

Can cosmic strangelets reach the earth?

The mechanism for the propagation of strangelets with low baryon number through the atmosphere of the Earth has been explored. It has been shown that under suitable initial conditions, such strangelets may indeed reach depths near mountain altitudes with mass numbers and charges close to the observed values in cosmic ray experiments.Comment: RevTeX text, with 3 encoded eps figures. To appear in Physical Review Letter

Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow

This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration

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

Numerical Validation of Experimental Heat Transfer Coefficient with SiO2 Nanofluid Flowing in a Tube with Twisted Tape Inserts

A numerical model has been developed for turbulent flow of nanofluids in a tube with twisted tape inserts. The model is based on the assumption that van Driest eddy diffusivity equation can be applied by considering the coefficient and the Prandtl index in momentum and heat respectively as a variable. The results from the numerical analysis are compared with experiments undertaken with SiO2/water nanofluid for a wide range of Reynolds number, Re. Generalized equation for the estimation of nanofluid friction factor and Nusselt number is proposed with the experimental data for twisted tapes. The coefficient and the Prandtl index in the eddy diffusivity equation of momentum and heat is obtained from the numerical values as a function of Reynolds number, concentration and twist ratio. An enhancement of 94.1 % in heat transfer coefficient and 160 % higher friction factor at Re = 19,046 is observed at a twist ratio of five with 3.0 % volumetric concentration when compared to flow of water in a tube. A good agreement with the limited experimental data of other investigators is observed with Al2O3 and Fe3O4 nanofluids indicating the validity of the numerical model for use with twisted tape inserts