Exact ground states and domain walls in one dimensional chiral magnets

We determine exactly the phase structure of a chiral magnet in one spatial dimension with the Dzyaloshinskii-Moriya (DM) interaction and a potential that is a function of the third component of the magnetization vector, n3, with a Zeeman (linear with the coefficient B) term and an anisotropy (quadratic with the coefficient A) term, constrained so that 2A ≤ |B|. For large values of potential parameters A and B, the system is in one of the ferromagnetic phases, whereas it is in the spiral phase for small values. In the spiral phase we find a continuum of spiral solutions, which are one-dimensionally modulated solutions with various periods. The ground state is determined as the spiral solution with the lowest average energy density. As the phase boundary approaches, the period of the lowest energy spiral solution diverges, and the spiral solutions become domain wall solutions with zero energy at the boundary. The energy of the domain wall solutions is positive in the homogeneous phase region, but is negative in the spiral phase region, signaling the instability of the homogeneous (ferromagnetic) state. The order of the phase transition between spiral and homogeneous phases and between polarized (n3 = ±1) and canted (n3 ≠ ±1) ferromagnetic phases is found to be second order.

Rechargeable Concrete Battery

A rechargeable cement-based battery was developed, with an average energy density of 7 Wh/m2 (or 0.8 Wh/L) during six charge/discharge cycles. Iron (Fe) and zinc (Zn) were selected as anodes, and nickel-based (Ni) oxides as cathodes. The conductivity of cement-based electrolytes was modified by adding short carbon fibers (CF). The cement-based electrodes were produced by two methods: powder-mixing and metal-coating. Different combinations of cells were tested. The results showed that the best performance of the rechargeable battery was the Ni–Fe battery, produced by the metal-coating method.

ANOMALOUS MODULATION OF THE WAVE FIELD IN A PLASMA WAVEGUIDE

The consequences of the development of the modulation instability of an intense wave field in a waveguide filled with plasma are considered. It is shown that in the mode of developed instability, the amplitude of the main wave under conditions of its weak absorption decreases by three to four times. The average energy density of the instability spectrum is almost twice the energy density of the main wave. The amplitude of the modulation envelope is three times the average amplitude of the main wave. The frequency of occurrence of anomalous modulation bursts is estimated.

Macroscale bending large-deformation and microbuckling behavior of a unidirectional fiber-reinforced soft composite

Due to microscale fiber microbuckling, a fiber-reinforced soft composite demonstrates large macroscale bending deformation (e.g. 10% reversible macroscale compressive strain), which is larger than that of a convenient fiber-reinforced plastics (e.g. 1.5–2% elongation/compression at break). To investigate the deformation behavior, a normalized average energy density of a fiber-reinforced soft composite laminate was derived. By using a self-consistent approach according to the minimum energy principle, a series of analytical expressions were derived by a simplified theoretical method through solving simplified partial differential equations of average energy density. Furthermore, an improved numerical calculation method was developed using the full four terms of partial differential equations of average energy density by employing the results of simplified theoretical method as initial calculating values. The dimensionless results demonstrated that the trend correlated well between those two methods, and the improved numerical method obtained more accurate results than those of the simplified theoretical method. Analytical and numerical results in normalized expressions systematically descripted the bending large-deformation behavior including position of neutral surface and critical buckling, wavelength, amplitude, shearing strain, macroscale compressive/tensile strain, buckled fiber strain, and actuation moment. To design a fiber-reinforced soft composite for use in engineering, the simplified theoretical method is used to predict trend and obtain approximate results for preliminary design, and the improved numerical method is further used to check and obtain more accurate results on detailed design stage.

Energy Density and Satiety of Meals Based on the Healthy Food Plate Model for Filipino Adults

Objective. This study aimed to determine the energy density and satiety of meals based on the healthy food plate model for Filipino adults. Methods. Thirteen healthy adult volunteers consumed breakfast test meals consisting of 1 cup go food, ½ cup grow food and 1 ½ cups glow food, following the recommended proportions in the plate model. Energy density (kcal/g) of the test meals was calculated. Feelings of hunger and fullness were assessed with 100-mm visual analogue scales (VAS) at pre-prandial (0 minute) and at 30, 60, 90, 120, 150, 180, and 240 minutes postprandial. Ghrelin levels at 0, 30, 60, 120, 180, and 240 minutes were determined by radioimmunoassay (RIA). Results. The test meals had an average energy density of 0.83 kcal/g. Hunger and fullness scores gradually changed with time but hunger remained significantly lower and fullness significantly higher than the pre-prandial levels at 180 minutes postprandial. Ghrelin declined after intake of the test meals and stayed significantly lower than the pre-prandial level at 240 minutes postprandial (30.21 ± 4.58 pmol/L). Conclusion. Meals following the recommendations in the healthy food plate model for Filipino adults have low energy density and its consumption sustained short-term satiety.

Research of Laser Cladding with SiC-316L Composite Coating on AZ31 Alloy

Laser cladding is an advanced material processing technology that has potential to improve the performances of metals. To improve the hardness and wear resistance of the surface of Magnesium alloy, SiC-316L composite coating on AZ31 magnesium alloy by laser cladding was generated, and the composition and properties analysis of the cladding coating were conducted. The results show that the laser cladding coating and the substrate achieve a good metallurgical bonding. The growth morphology of boundary is mainly branch dendrite.When the laser power is 1250 W, spot diameter is 2mm, scanning speed is 25 mm/s and average energy density is 2.5×104J, the cladding layer possesses the best micro-hardness, about 3 times as hard as the substrate.

THE GRAVITATIONAL ENERGY PROBLEM FOR COSMOLOGICAL MODELS IN TELEPARALLEL GRAVITY

We present a method to calculate the gravitational energy when asymptotic boundary conditions for the space–time are not given. This is the situation for most of the cosmological models. The expression for the gravitational energy is obtained in the context of the teleparallel equivalent of general relativity. We apply our method first to the Schwarzschild–de Sitter solution of Einstein's equation, and then to the Robertson–Walker universe. We show that in the first case our method leads to an average energy density of the vacuum space–time, and in the latter case the energy vanishes in the case of null curvature.

Duration of lactation and postweaning changes in mass and body composition of harbour seal, Phoca vitulina, pups

We studied changes in body mass and body composition of harbour seal pups from weaning to 5 – 6 weeks postweaning in June – August 1988 and 1989 on Sable Island, Canada. Known-age pups (n = 52) were captured at 3-day intervals from late lactation through about 40 days postweaning. Pups were weaned, on average, at 24.1 ± 0.44 days (mean ± SE) postpartum at a body mass of 24.9 ± 0.45 kg. There were no significant differences between years or sexes in the age and mass at weaning or in the rate of mass loss during the postweaning period. The duration of the postweaning fast averaged from 15 – 17 days as assessed by stomach lavage. The rate of mass loss was independent of weaning mass. At weaning, pups contained an average of 47.7% water and 32.8% fat, based on deuterium oxide dilution. During the first 14 days postweaning, the estimated body composition of pups did not change, despite the loss of body mass. Over the next 26 days, the estimated percent body water increased to about 63% and body fat declined to about 12%. The average energy density of harbour seal pups at weaning was low (16.3 kJ/g) compared with that of other phocids (17.7 – 22.2 kJ/g). This low energy density at weaning may reflect the highly aquatic and precocial development of harbour seal pups.