Bulk Density Protocol

The purpose of this resource is to measure the bulk density of each horizon in a soil profile. In the field, students collect three soil samples from each horizon in a soil profile using a container with a measured volume. In the classroom, students weigh the samples, dry them, and weigh them again to determine their dry mass and water content. Students then sieve the dry soil samples and measure the mass and volume of any rocks and material with dimensions greater than 2 mm. Students use the Bulk Density Data Sheet to calculate the soil bulk density for each sample. Educational levels: Middle school, High school

Pembuatan dan Pengujian Bulk Density, Fluks Magnetik, dan Mikrostruktur pada Hybrid Magnet Berbasis NdFeB / BaFe12O19

Telah dilakukan pembuatan hybrid magnet permanen berbasis NdFeB dengan penambahan BaFe12O19 ( 5, 10, 15, dan 20 % wt). Aplikasi hybrid magnet permanen NdFeB untuk komponen motor dan generator listrik skala kecil. Tujuan penelitian ini adalah untuk mengetahui pengaruhnya penambahan BaFe12O19 terhadap densitas, fluks magnetik dan mikrostruktur dari hybrid magnet NdFeB. Proses preparasi bahan baku mulai dari pencampuran serbuk NdFeB tipe MQP-B+ dengan BaFe12O19, digerus dan dicampur bahan perekat Epoxy Resin sebanyak 6 %wt dan dicetak dengan gaya 8 tonf sehingga membentuk pellet dengan diameter 18,5 dan tebal 4,3 mm. Sampel yang telah dicetak kemudian dikeringkan pada kondisi vacuum (±15 mbar) dengan temperatur 80°C ditahan selama 1 jam. Karakterisasi yang dilakukan meliputi pengukuran bulk density, microstructurer menggunakan Optical Microscope dan sifat magnet dengan menggunakan Gaussmeter. Dari hasil karakterisasi secara keseluruhan diperoleh kondisi optimum pada komposisi hybrid magnet NdFeB adalah 95% NdFeB, 5 %wt BaFe12O19 . Sifat-sifat hybrid magnet NdFeB tersebut adalah bulk density = 4,469 g/cm3, Fluks magnetik = 1029,85 Gauss, ukuran bulir (grain size) sekitar 4,1 – 5,2 µm

Density and conformation with relaxed substrate, bulk, and interface electrophoretic deposition of polymer chains

Characteristics of relaxed density profile and conformation of polymer chains are studied by a Monte Carlo simulation on a discrete lattice in three dimensions using different segmental (kink-jump $K$, crank-shaft $C$, reptation $R$) dynamics. Three distinct density regimes, substrate, bulk, and interface, are identified. With the $KC$ segmental dynamics we find that the substrate coverage grows with a power-law, $d_s \propto t^{\gamma}$ with a field dependent nonuniversal exponent $\gamma = 0.23 + 0.7 E$. The bulk volume fraction $d_b$ and the substrate polymer density ($d_s$) increases exponentially with the field ($d_b \propto E^{0.4}$, $d_s \propto E^{0.2}$) in the low field regime. The interface polymer density $d_f$ increases with the molecular weight. With the $KCR$ segmental dynamics, bulk and substrate density decreases linearly with the temperature at high temperatures. The bulk volume fraction is found to decay with the molecular weight, $d_b \propto L_c^{-0.11}$. The radius of gyration remains Gaussian in all density regions.Comment: Changed double to single spacin

Microwave performance of high-density bulk MgB2

We have performed microwave measurements on superconducting hot-isostatically- pressed (HIPed) bulk MgB2 using a parallel-plate resonator technique. The high density and strength of the HIPed material allowed preparation of samples with mirror-like surfaces for microwave measurements. The microwave surface resistance decreased by about 40% at 20 K when the root-mean-square surface roughness was reduced from 220 nm to 110 nm through surface-polishing and ion-milling. The surface resistance was independent of surface microwave magnetic field at least up to 4 Oe and below 30 K. We attribute this behavior, and the overall low surface resistance (~0.8 mOhms at 10 GHz and 20 K), to the high density of our samples and the absence of weak links between grains

Magnetic levitation force between a superconducting bulk magnet and a permanent magnet

The current density in a disk-shaped superconducting bulk magnet and the magnetic levitation force exerted on the superconducting bulk magnet by a cylindrical permanent magnet are calculated from first principles. The effect of the superconducting parameters of the superconducting bulk is taken into account by assuming the voltage-current law and the material law. The magnetic levitation force is dominated by the remnant current density, which is induced by switching off the applied magnetizing field. High critical current density and flux creep exponent may increase the magnetic levitation force. Large volume and high aspect ratio of the superconducting bulk can enhance the magnetic levitation force further.Comment: 18 pages and 8 figure

Fluctuations of water near extended hydrophobic and hydrophilic surfaces

We use molecular dynamics simulations of the SPC-E model of liquid water to derive probability distributions for water density fluctuations in probe volumes of different shapes and sizes, both in the bulk as well as near hydrophobic and hydrophilic surfaces. To obtain our results, we introduce a biased sampling of coarse-grained densities, which in turn biases the actual solvent density. The technique is easily combined with molecular dynamics integration algorithms. Our principal result is that the probability for density fluctuations of water near a hydrophobic surface, with or without surface-water attractions, is akin to density fluctuations at the water-vapor interface. Specifically, the probability of density depletion near the surface is significantly larger than that in bulk. In contrast, we find that the statistics of water density fluctuations near a model hydrophilic surface are similar to that in the bulk

Population inversion of a NAHS mixture adsorbed into a cylindrical pore

A cylindrical nanopore immersed in a non-additive hard sphere binary fluid is studied by means of integral equation theories and Monte Carlo simulations. It is found that at low and intermediate values of the bulk total number density the more concentrated bulk species is preferentially absorbed by the pore, as expected. However, further increments of the bulk number density lead to an abrupt population inversion in the confined fluid and an entropy driven prewetting transition at the outside wall of the pore. These phenomena are a function of the pore size, the non-additivity parameter, the bulk number density, and particles relative number fraction. We discuss our results in relation to the phase separation in the bulk.Comment: 7 pages, 8 Figure

Thermodynamic properties and bulk viscosity near phase transition in the Z(2) and O(4) models

We investigate the thermodynamic properties including equation of state, the trace anomaly, the sound velocity and the specific heat, as well as transport properties like bulk viscosity in the Z(2) and O(4) models in the Hartree approximation of Cornwall-Jackiw-Tomboulis (CJT) formalism. We study these properties in different cases, e.g. first order phase transition, second order phase transition, crossover and the case without phase transition, and discuss the correlation between the bulk viscosity and the thermodynamic properties of the system. We find that the bulk viscosity over entropy density ratio exhibits an upward cusp at the second order phase transition, and a sharp peak at the 1st order phase transition. However, this peak becomes smooth or disappears in the case of crossover. This indicates that at RHIC, where there is no real phase transition and the system experiences a crossover, the bulk viscosity over entropy density might be small, and it will not affect too much on hadronization. We also suggest that the bulk viscosity over entropy density ratio is a better quantity than the shear viscosity over entropy density ratio to locate the critical endpoint.Comment: 19 pages, 30 figures, 1 tabl