Simulation of granular soil behaviour using the bullet physics library

A physics engine is computer software which provides a simulation of certain physical systems, such as rigid body dynamics, soft body dynamics and fluid dynamics. Physics engines were firstly developed for using in animation and gaming industry ; nevertheless, due to fast calculation speed they are attracting more and more attetion from researchers of the engineering fields. Since physics engines are capable of performing fast calculations on multibody rigid dynamic systems, soil particles can be modeled as distinct rigid bodies. However, up to date, it is not clear to what extent they perform accurately in modeling soil behaviour from a geotechnical viewpoint. To investigate this, examples of pluviation and vibration-induced desification were simulated using the physics engine called Bullet physics library. In order to create soil samples, first, randomly shaped polyhedrons, representing gravels, were generated using the Voronoi tessellation approach. Then, particles were pluviated through a funnel into a cylinder. Once the soil particles settled in a static state, the cylinder was subjected to horizontal sinusoidal vibration for a period of 20 seconds. The same procedure for sample perparation was performed in the laboratory. The results of pluviation and vibration tests weere recorded and compared to those of simulations. A good agreement has been found between the results of simulations and laboratory tests. The findings in this study reinforce the idea that physics engines can be employed as a geotechnical engineering simulation tool

Synthesis of medium-chain glycerides using lipase from Candida rugosa

Enzymatic synthesis of medium-chain glycerides (MCG) from capric acid and glycerol was studied using lipase from Candida rugosa. The effects of various reaction parameters such as time, molar ratio of substrates (mmol capric acid/mmol glycerol), amount of lipase, type of organic solvents, and initial water activity (a w ) were studied. The best conditions tested for MCG synthesis at 37°C were, respectively, time, 24 h; molar ratio of substrates, 2.5; and amount of lipase, 100.0 mg. The use of organic solvents greatly influenced the activity of lipase in the synthesis of MCG. Generally, activity of lipase was high in nonpolar solvents with log P values from 3.50 to 4.50, where P is the partition coefficient between water and 1-octanol. The enzymatic synthesis of MCG was preferably carried out at an initial a w of 0.328, which resulted in maximal yield. Analysis of the products of reaction using gas chromatography showed that lipase from Candida rugosa seemed to produce more dicaprin and tricaprin than monocaprin

ANALISIS PENGARUH HUBUNGAN ANTAR MANUSIA,KONDISI FISIK LINGKUNGAN KERJA DAN BEBAN KERJA TERHADAP KINERJA KARYAWAN PADA PT. CHEETHAM GARAM INDONESIA DI KABUPATEN NAGEKEO

This study aims to determine the effect of human relationships, physical conditions of the work environment and workload on employee performance at PT. Indonesian salt cheetham in Nagekeo Regency. Types of causality research. The data analysis technique is multiple linear regression analysis. The research sample was 73 people. The sampling technique is random sampling. The results of the t-statistical test show that the relationship between humans, the physical condition of the work environment has an effect on employee performance, while the workload variable has no effect on employee performance. The results of the F test show that the variables X1, X2, X3 simultaneously affect Y

Accretion-Induced Lithium Line Enhancements in Classical T Tauri Stars: RW Aur

It is widely accepted that much of the stochastic variability of T Tauri stars is due to accretion by a circumstellar disk. The emission line spectrum as well as the excess continuum emission are common probes of this process. In this communication, we present additional probes of the circumstellar environment in the form of resonance lines of low ionization potential elements. Using a set of 14 high resolution echelle observations of the classical T Tauri star (CTTS), RW Aur, taken between 1986 and 1996, we carefully measure the continuum veiling at each epoch by comparing more than 500 absorption lines with those of an appropriate template. This allows us to accurately subtract out the continuum emission and to recover the underlying photospheric spectrum. In doing so, we find that selected photospheric lines are enhanced by the accretion process, namely the resonance lines of LiI and KI. A resonance line of TiI and a low excitation potential line of CaI also show weak enhancements. Simple slab models and computed line bisectors lead us to propose that these line enhancements are markers of cool gas at the beginning of the accretion flow which provides an additional source of line opacity. These results suggest that published values of surface lithium abundances of classical T Tauri stars are likely to be overestimated. This would account for the various reports of surface lithium abundances in excess of meteoritic values among the extreme CTTS. Computing LTE lithium abundances of RW Aur in a low and then high accretion state yields abundances which vary by one order of magnitude. The low accretion state lithium abundance is consistent with theoretical predictions for a star of this age and mass while the high accretion state spectrum yields a super-meteoritic lithium abundance.Comment: 28 pages, 8 figures, accepted by Ap