Ab initio study on the magneto-structural properties of MnAs

The magnetic and structural properties of MnAs are studied with ab initio methods, and by mapping total energies onto a Heisenberg model. The stability of the different phases is found to depend mainly on the volume and on the amount of magnetic order, confirming previous experimental findings and phenomenological models. It is generally found that for large lattice constants the ferromagnetic state is favored, whereas for small lattice constants different antiferromagnetic states can be stabilized. In the ferromagnetic state the structure with minimal energy is always hexagonal, whereas it becomes orthorhombically distorted if there is an antiferromagnetic component in the hexagonal plane. For the paramagnetic state the stable cell is found to be orthorhombic up to a critical lattice constant of about 3.7 Angstrom, above which it remains hexagonal. This leads to the second order structural phase transition between paramagnetic states at about 400 K, where the lattice parameter increases above this critical value with rising temperature due to the thermal expansion. For the paramagnetic state an analytic approximation for the magnitude of the orthorhombic distortion as a function of the lattice constant is given. Within the mean field approximation the dependence of the Curie temperature on the volume and on the orthorhombic distortion is calculated. For orthorhombically distorted cells the Curie temperature is much smaller than for hexagonal cells. This is mainly due to the fact that some of the exchange coupling constants in the hexagonal plane become negative for distorted cells. With these results a description of the susceptibility as function of temperature is given

Molasses Injection to Improve Growth and Vitality of Kesambi (Schleicera Oleosa Merr) as Lac Insect Host Plant

Lac is a non-timber forest product derived from the secretion of Laccifer lacca insects that are cultivated in kesambi tree (Schleicera oleosa Merr). Low lac production in Indonesia due to poor conditions of host plant indicated by poor growth symptoms, yellowing, and falling leaves. The aim of this research was to study the effect of molasses injection on the growth and vitality of kesambi tree. Molasses were injected into the plant using passive liquid injection methods. Pre-research activities were carried out by the tree trunk injection in 0.5, 1.5, and 2 meters above the ground using gentian violet to determine the best stem injection position, while the main research activity was performed by injection of the kesambi tree trunk using molasses in concentrations of 5, 10, 15% and water as control. The parameters measured at the pre-study was translocation length of gentian violet whereas at the main research were the volume uptake, the increase of branch diameter growth, total sugar content and chlorophyll content. Pre-research results showed that 1.5 meters above the ground is the best injection position. The main research results indicated that the highest volume uptake was water followed by others treatments. Molasses injection at concentration of 10% gives better effect on the increase of branch diameter growth (4.3 mm), obtained sugar content in 18.46%. The vitality of kesambi tree also increased by the molasses injection at concentration of 10%. It was shown by thein creased of chlorophyll a (1.117 mg/g), b (0.416), carotene (0.365), and Anthocyanin (0.094 mg/100g)

On the Frequency Dependency of Radio Channel's Delay Spread: Analyses and Findings From mmMAGIC Multi-frequency Channel Sounding

This paper analyzes the frequency dependency of the radio propagation channel's root mean square (rms) delay spread (DS), based on the multi-frequency measurement campaigns in the mmMAGIC project. The campaigns cover indoor, outdoor, and outdoor-to-indoor (O2I) scenarios and a wide frequency range from 2 to 86 GHz. Several requirements have been identified that define the parameters which need to be aligned in order to make a reasonable comparison among the different channel sounders employed for this study. A new modelling approach enabling the evaluation of the statistical significance of the model parameters from different measurements and the establishment of a unified model is proposed. After careful analysis, the conclusion is that any frequency trend of the DS is small considering its confidence intervals. There is statistically significant difference from the 3GPP New Radio (NR) model TR 38.901, except for the O2I scenario.Comment: This paper has been accepted to the 2018 12th European Conference on Antennas and Propagation (EuCAP), London, UK, April 201

Surface pinning in amorphous ZrTiCuNiBe alloy

We have measured the amplitude and the phase of an electromagnetic (EM) field radiated from superconductor (amorphous ZrTiCuNiBe alloy) in the mixed state due to interaction of the flux lattice with an elastic wave. The results undoubtedly point to an essential contribution of a surface pinning into the flux lattice dynamics. We propose a model that describes radiation of EM field from superconductors with non-uniform pinning. The model allows to reconstruct the viscosity and the Labush parameters from the experimental data. The behavior of the Labush parameter can be qualitatively explained in terms of the collective pinning theory with the allowance of thermal fluctuations.Comment: 4 pages, 4 figure

Serangan Arthroschista Hilaralis Walk. (Lepidoptera: Pyralidae) pada Tegakan Jabon (Neolamarckia Cadamba [Roxb.] Bosser) di Sumatera Selatan

Serangan hama merupakan masalah utama yang dihadapi dalam budi daya jabon (Neolamarckia cadamba [Roxb.] Bosser) di Indonesia khususnya di Sumatera Selatan. Arthroschista hilaralis Walk. (Lepidoptera: Pyralidae) merupakan salah satu hama penting yang menyerang tanaman jabon. Informasi mengenai tingkat serangan A. hilaralis pada tegakan jabon diperlukan sebagai bahan pertimbangan pengelolaan A. hilaralis. Tujuan penelitian ini adalah mengkaji insidensi dan intensitas serangan A. hilaralis yang menyerang tegakan jabon umur 2 dan 4 tahun selama 2 musim pengamatan, serta mengkaji pengaruh faktor cuaca (suhu dan kelembaban udara) terhadap serangan A. hilaralis. Penelitian ini dilaksanakan pada 6 lokasi yang terletak pada beberapa daerah di Sumatera Selatan. Pada setiap lokasi penelitian ditentukan 3 plot masing-masing seluas 0,03 ha dan berisi 20 tanaman jabon. Pengamatan insidensi dan intensitas serangan A. hilaralis dilakukan sebulan sekali selama 16 bulan yang mewakili 2 kategori waktu pengamatan, yaitu musim hujan dan musim kemarau. Hasil penelitian menunjukkan bahwa serangan A. hilaralis paling tinggi terjadi pada tegakan jabon umur 2 tahun dan pada musim hujan dengan insidensi dan intensitas serangan masing-masing sebesar 74,45% dan 55,21%. Faktor cuaca (suhu dan kelembaban udara) berpengaruh terhadap tingkat serangan A. hilaralis. Suhu udara berkorelasi negatif terhadap insidensi (r = -0,629; p = 0,009) dan intensitas serangan A. hilaralis (r = -0,546; p = 0,029), sedangkan kelembaban udara berkorelasi positif terhadap insidensi (r = 0,900; p < 0,0001) dan intensitas serangan A. hilaralis (r = 0,768; p = 0,0005)

Parametric study on push-up loading of sand plug in open-ended pipe pile using DEM

金沢大学理工研究域環境デザイン学系The bearing capacity of an open-ended pipe pile consists of outer shaft resistance, toe resistance and soil plug resistance (inner shaft resistance). The soil plug capacity is thought to be largely controlled by height and stress states of soil plug that is formed inside the pile during installation process. However, these aspects have not been fully clarified. In this paper, parametric study on push-up loading of soil plug was carried out using three-dimensional discrete element method for the first step to investigate the bearing mechanism of open-ended pipe pile. Influence of dilatancy of sand and the soil plug height was focused. © 2006 Taylor & Francis Group

Finite-Size and surface effects in maghemite nanoparticles: Monte Carlo simulations

Finite-size and surface effects in fine particle systems are investigated by Monte Carlo simulation of a model of a $\gamma$-Fe$_2$O$_3$ (maghemite) single particle. Periodic boundary conditions have been used to simulate the bulk properties and the results compared with those for a spherical shaped particle with free boundaries to evidence the role played by the surface on the anomalous magnetic properties displayed by these systems at low temperatures. Several outcomes of the model are in qualitative agreement with the experimental findings. A reduction of the magnetic ordering temperature, spontaneous magnetization, and coercive field is observed as the particle size is decreased. Moreover, the hysteresis loops become elongated with high values of the differential susceptibility, resembling those from frustrated or disordered systems. These facts are consequence of the formation of a surface layer with higher degree of magnetic disorder than the core, which, for small sizes, dominates the magnetization processes of the particle. However, in contradiction with the assumptions of some authors, our model does not predict the freezing of the surface layer into a spin-glass-like state. The results indicate that magnetic disorder at the surface simply facilitates the thermal demagnetization of the particle at zero field, while the magnetization is increased at moderate fields, since surface disorder diminishes ferrimagnetic correlations within the particle. The change in shape of the hysteresis loops with the particle size demonstrates that the reversal mode is strongly influenced by the reduced atomic coordination and disorder at the surface.Comment: Twocolumn RevTex format. 19 pages, 15 Figures included. Submitted to Phys. Rev.