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The aim of this study is to build a science kit of Faraday’s Law with free fall motion method. The magnetic flux comes from several neodymium magnets and the coil is made of copper. The moving magnet falling through the coil causes a change in the magnetic flux and produces an induced emf. The data analysis technique used in this research are graphical method and analysis of Faraday’s Law equations with another supporting equation. Based on the results of this study, the conclusion is the induced emf value is directly proportional with the change of the magnetic flux and also has a directly proportional with the number of turn of coil, thus it can be obtained the mathematical equation of Faraday’s Law ε = d ϕ B d t

The combustion of aluminum agglomerate particles with a diameter of 215–840 μm in free fall in air at atmospheric pressure has been studied. The main events of the combustion of particles after their release from the sample into air—the transition from symmetric to asymmetric combustion, fragmentation, and the end of combustion—are characterized by corresponding times. Approximating dependences on the particle diameter were obtained for the characteristic times of symmetric combustion, the beginning of fragmentation, the end of fragmentation, and the end of combustion. The characteristics of particle fragmentation were determined. Data are presented on the relative number of mother agglomerate particles ejecting a given number of fragments and on the dependence of the number of fragments on the burning particle diameter. For larger particles, fragmentation begins later, but proceeds more intensely. In general, the observed spontaneous fragmentation of aluminum agglomerates is insignificant; therefore, to reduce their burning time, it is necessary to enhance the fragmentation process.

The combustion of aluminum agglomerate particles with a diameter of 215–840 µm in free fall in air at atmospheric pressure has been studied. As the particles burn out, the initially spherically symmetric combustion is replaced by an asymmetric one, fragmentation occurs, and the combustion process ultimately ends with the formation of an oxide residue. These events are characterized by corresponding times. In this paper, the duration of the symmetric combustion stage is determined to be on average 0.5 ± 0.1 of the combustion time. Empirical approximating dependences of the coordinate x ( t ) and velocity ( t ) on time are obtained for particles of different diameters. Analytical calculations of the motion of burning particles were performed assuming that the viscosity of air in the vicinity of the particle is 6.98 × 10 –5 Pa s, which corresponds to an average temperature of 2005 K. By comparing the empirical and calculated dependences x ( t ) and ( t ), the dependence of the effective aerodynamic drag coefficient of the particle on its size was determined in the form C d ( D , Re) = (9.33 + 0.13 D )/Re, where Re is the Reynolds number from the range 0.2 < Re < 5.2. For estimations, C d = 77/Re can be used.

From the producers’ point of view, there is no universal and quick method to predict bruise area when dropping an apple from a certain height onto a certain type of substrate. In this study the authors presented a very simple method to estimate bruise volume based on drop height and substrate material. Three varieties of apples were selected for the study: Idared, Golden Delicious, and Jonagold. Their weight, turgor, moisture, and sugar content were measured to determine morphological differences. In the next step, fruit bruise volumes were determined after a free fall test from a height of 10 to 150 mm in 10 mm increments. Based on the results of the research, linear regression models were performed to predict bruise volume on the basis of the drop height and type of substrate on which the fruit was dropped. Wood and concrete represented the stiffest substrates and it was expected that wood would respond more subtly during the free fall test. Meanwhile, wood appeared to react almost identically to concrete. Corrugated cardboard minimized bruising at the lowest discharge heights, but as the drop height increased, the cardboard degraded and the apple bruising level reached the results as for wood and concrete. Contrary to cardboard, the foam protected apples from bruising up to a drop height of 50 mm and absorbed kinetic energy up to the highest drop heights. Idared proved to be the most resistant to damage, while Golden Delicious was medium and Jonagold was least resistant to damage. Numerical models are a practical tool to quickly estimate bruise volume with an accuracy of about 75% for collective models (including all cultivars dropped on each of the given substrate) and 93% for separate models (including single cultivar dropped on each of the given substrate).

The seabed surface provides habitat for abundant and diverse fauna, whose burrowing activities have been shown to modify geotechnical properties of surface sediments. Whether these impacts affect geotechnical properties on larger scales of traditional measurements has not been well studied. This study represents an initial attempt to assess whether infaunal activity affects seabed properties on a scale relevant for, and therefore, detectable in portable free fall penetrometer measurements. Specifically, we examine sediment strength profiles of the upper 10–70 cm of sandy (poorly graded sand and muddy sand) seabed sediments in Mobile Bay, Alabama, USA, hypothesizing that infauna create heterogeneity in sediment structure that would lead to variability in PFFP vertical profiles as well as among replicate measurements at a site. Sediments were composed predominantly of sands, with only 17% of the sites featuring sand contents < 97% and median grain sizes ranging from 0.0987 to 0.3457 mm. Sediment strength generally decreased with a decreasing sand content, but variability was not explained by sand content alone. PFFP impacts in sandier sites (> 97% sand) were limited to the surface few cm, but considerable vertical and spatial variability in muddy sands and lower strength at sites with abundant burrowing infauna suggest that infaunal activities may affect PFFP measurements in these sediments.

Seed dispersal by wind is one of the most important dispersal mechanisms in plants. The key seed trait affecting seed dispersal by wind is the effective terminal velocity (hereafter “terminal velocity”, Vt), the maximum falling speed of a seed in still air. Accurate estimates of Vt are crucial for predicting intra‐ and interspecific variation in seed dispersal ability. However, existing methods produce biased estimates of Vt for slow‐ or fast‐falling seeds, fragile seeds, and seeds with complex falling trajectories. We present a new video‐based method that estimates the falling trajectory and Vt of wind‐dispersed seeds. The design involves a mirror that enables a camera to simultaneously record a falling seed from two perspectives. Automated image analysis then determines three‐dimensional seed trajectories at high temporal resolution. To these trajectories, we fit a physical model of free fall with air resistance to estimate Vt. We validated this method by comparing the estimated Vt of spheres of different diameters and materials to theoretical expectations and by comparing the estimated Vt of seeds to measurements in a vertical wind tunnel. Vt estimates closely match theoretical expectations for spheres and vertical wind tunnel measurements for seeds. However, our Vt estimates for fast‐falling seeds are markedly higher than those in an existing trait database. This discrepancy seems to arise because previous estimates inadequately accounted for seed acceleration. The presented method yields accurate, efficient, and affordable estimates of the three‐dimensional falling trajectory and terminal velocity for a wide range of seed types. The method should thus advance the understanding and prediction of wind‐driven seed dispersal. Accurate estimates of seed terminal velocity, the key seed trait affecting seed dispersal by wind, are crucial for predicting intra‐ and interspecific variation in seed dispersal ability. However, existing methods produce biased estimates of terminal velocity for slow‐ or fast‐falling seeds, fragile seeds, and seeds with complex falling trajectories. We present a new video‐based method that yields accurate, efficient and affordable estimates of the three‐dimensional falling trajectory and terminal velocity for a wide range of seed types, and should thus advance the understanding and prediction of wind‐driven seed dispersal.

Metal powder is used in the Powder Metallurgy (PM) application process. Most of the metals used in the PM are stainless steel made by the gas atomization process. This study uses the free fall gas atomizer. The material was used to produce the metal powder from various forms of stainless steel 304 raw material, which is melted in an electric induction furnace. This method is very practical to be applied in the large-scale metal processing industries. While the gas pressure variation results show that metal powder with a smaller size will be produced more using high gas pressure. The free fall gas atomizer has successfully produced stainless steel 304 metal powder with the size <40 μm and have a spherical shape. The well-rounded sphericity for 8 bar pressure, 10 bar pressure, and 12 bar pressure are 61.1%, 41.7%, and 37.5% respectively. It can be concluded that 12 bar pressure produces the smallest size range of powder about <40 µm with the most quantity about 1.11%wt, followed by 10 bar pressure about 0.41%wt and 8 bar pressure about 0.07%wt.

The water entry problem of a wedge through free fall in three degrees of freedom is studied through the velocity potential theory for the incompressible liquid. In particular, the effect of the body rotation is taken into account, which seems to have been neglected so far. The problem is solved in a stretched coordinate system through a boundary element method for the complex potential. The impact process is simulated based on the time stepping method. Auxiliary function method has been used to decouple the mutual dependence between the body motion and the fluid flow. The developed method is verified through results from other simulation and experimental data for some simplified cases. The method is then used to undertake extensive investigation for the free fall problems in three degrees of freedom.

Metal Injection Molding (MIM) is an application of Powder Metallurgy (PM) and Plastic Injection Molding currently being developed to produce precisely-small components. Most of the metal applications using PM are stainless steel fabricated by a gas atomizer. In this study, an atomizer is designed and fabricated to produce stainless steel powder by using a free fall gas atomization method. The stainless steel used in this study is AISI 304 atomized with the diameter sizes varying from about 3 mm, 5 mm, and 7 mm. The variables of diameter size results are the lowest melt flow rate produces the smallest mean diameter, but no significant difference on the sphericity of powder morphology. While the gas pressure variation results shows that metal powder with smaller size will be produced more using the high gas pressure. The gas atomizer have successfully produced metal powder with the size <40 μm and have a spherical shape. The well rounded sphericity for melt flowrate 0.41x10-3 m3/min, 1.14 x10-3 m3/min, and 2.24x10-3 m3/min are 60.0%, 36.0%, and 55.2% respectively.

Cooling massive particles to the quantum ground state allows fundamental tests of quantum mechanics to be made; it would provide an experimental probe of the boundary between the classical and quantum worlds. Delić et al. laser-cooled an optically trapped solid-state object (a ∼150-nanometer-diameter silic a nanoparticle) into its quantum ground state of motion starting from room temperature. Because the object is levitated using optical forces, the experimental configuration can be switched to free fall, thereby providing a test bed for several macroscopic quantum experiments. Science , this issue p. 892 A levitated nanoparticle trapped in an optical cavity is cooled to the quantum ground state. Quantum control of complex objects in the regime of large size and mass provides opportunities for sensing applications and tests of fundamental physics. The realization of such extreme quantum states of matter remains a major challenge. We demonstrate a quantum interface that combines optical trapping of solids with cavity-mediated light-matter interaction. Precise control over the frequency and position of the trap laser with respect to the optical cavity allowed us to laser-cool an optically trapped nanoparticle into its quantum ground state of motion from room temperature. The particle comprises 10 8 atoms, similar to current Bose-Einstein condensates, with the density of a solid object. Our cooling technique, in combination with optical trap manipulation, may enable otherwise unachievable superposition states involving large masses.