The effect of borax addition to aluminum alloy produced by powder metallurgy on mechanical and thermophysical properties

Purpose Lightweight, durable and economical materials production has gained considerable importance according to the needs of developing technology. The purpose of this paper is to develop an new aluminum alloy by powder metalurgy. Design/methodology/approach Powder metallurgy, which provides controllably on desired end product, method was applied. Aluminum alloy was created with Al, Zn, Mg, Cu powders and 1.5% Na2[B4O5(OH)4].8H2O added. It was pressed under high pressure and sintered at 600 °C under N2 gas atmosphere. Density, hardness behaviors and thermal properties were determined. Surfaces and crystal structures of samples were characterized. Findings The addition of borax made easier grains coming to together, acting as binders and the AlB2 crystal phase was formed. It was also observed that MgZn2, Al2CuMg phases were formed. In this way, the pores between the particles of the material were reduced from 35% to 5% total porosity and the hardness of the material was increased 29 N/mm2 to 45 N/mm2 (Brinell Hardness, HB). The surface properties improved and the hydrophobicity of the surface (from 63° to 102° contact angle with borax) increased. Thus, the heat transfer among atoms get easier and the borax addition decreased specific heat capacity and enthalpy of aluminum–borax samples. This situation was also simulated with the heat transfer module of COMSOL. As result, the energy required reduced. In the other word, sintering process occurred at low temperature and more efficient. Originality/value New aluminum alloy has been created from different amounts of Zn, Mg, Cu elemental powders. In addition to literature, relationship of borax and aluminum and other alloying elements on the mechanical, thermophysical and surface properties of new obtained aluminum alloy has been investigated.

Simulation of Gravity Wave D-region disturbance and its effect on the LWPC simulated VLF signal

In this work we show the result of the numerical simulation of the gravity waves (GWs) D region disturbance. Effectively, using the Glukhov-Pasko-Inan (GPI) model of the electron density in the D region we were figured out the response of the electron density due to gravity wave neutral atmosphere oscillation. As a consequence to the D region disturbance, the electron density sometimes increases when the neutral atmosphere density decreases and vice versa. This behavior was interpreted by the decreases or increases of ionization rate by chemical loss process. In a second simulation work, we used the Long Wave Propagation Capability (LWPC) code to simulate the Very Low Frequency (VLF) signal when the gravity wave disturbance crossed the VLF path. The effect of the disturbance is to decrease the VLF signal reflection height below the ambient altitude (87 km) when the electron density increases. On the other hand and when the electron density drops, the VLF reflection altitude increased higher than 87 km.

Capabilities for Probing of Upper Atmosphere Density Variations and Seismic-Orbital Effects Using Small-Size Spacecraft

The miniature spacecraft have a high ballistic coefficient, which is advantageous for the resolution of sensing the density of the upper atmosphere. The purpose of this work is to show new features of the "falling spheres method" based on the miniaturization of the Spacecraft. The "falling spheres method" is used to probe variations in the density of the upper atmosphere.A technical solution for diagnostics of orbital sections with abnormal changes in the speed and acceleration of spacecraft equipped with onboard navigation receivers and micro-accelerometers is considered.The technical result of the proposed development is the efficiency and cost – effectiveness of sounding variations in the density of the upper atmosphere, seismic-orbital effects-variations in the density of the atmosphere over earthquake-regions and the seismic hazard.

Derivative-free Nonlinear Version of Extended Recursive Three-step Filter for State and Parameter Estimation during Mars Entry

Parameter uncertainties which may lead to divergence of traditional Kalman filters during Mars entry are investigated in this paper. To achieve high precision navigation, a Derivative-free Nonlinear version of an Extended Recursive Three-Step Filter (DNERTSF) is introduced, which suits nonlinear systems with arbitrary parameter uncertainties. A DNERTSF can estimate the state and the parameters simultaneously, and Jacobian and Hessian calculations are not necessary for this filter. Considering the uncertainties in atmosphere density, ballistic coefficient and lift-to-drag ratio, a numerical simulation of Mars entry navigation is carried out. Compared with the standard Unscented Kalman Filter (UKF), DNERTSF can effectively reduce the adverse effects of parameter uncertainties and achieve a high navigation accuracy performance, keeping position and velocity estimation errors at a very low level. In all, the DNERTSF in this paper shows good advantages for Mars entry navigation, providing a possible application for a future Mars pinpoint landing.

The analysis of atmospheric factors affecting the value of vertical refraction angle with the assessment of the importance of introduction of the atmospheric amendment

The study of vertical displacements of hydrotechnical objects, slender constructions, opencast mines or flotation waste reservoirs often requires continuous geodetic monitoring, which in real time defines potential threats resulting from changes in the geometry of the object. In order to ensure high accuracy in determining vertical displacements, a precise robotic tacheometer is used as one of the monitoring sensors. In the case of trigonometric leveling, the quality of measurements is affected not only by the accuracy of the instrument, but also by the centre through which the laser beam emitted by it passes. The radius emitted by the tacheometer due to the layered structure of the atmosphere is deflected, and the angle that it creates with the theoretical course of rays is called the angle of vertical refraction. In order to eliminate the influence of this type of errors, so-called atmospheric correction is introduced to all tacheometric measurements. Currently, total stations automatically determine and introduce corrections for observation, usually using only air temperature and atmospheric pressure. However, the number of factors responsible for the change in atmosphere density, and thus the deflection of the laser beam is much greater. And its influence is also affected by the length of the target and roughness of the area over which the measurement is made. The paper presents the analysis of the significance of various atmospheric and terrain factors that may affect the value of the vertical refraction angle. By the multiple regression method, with the use of the analyzed factors, equations describing the phenomenon of vertical refraction for four seasons have been designated. The defined equation coefficients were used to determine the refraction angle for the observations recorded on the post-flotation waste tank. To confirm the rightness of introducing an additional atmospheric correction, analyses were performed showing the percentage of corrected results.

Atmosphere Density Measurements Using GPS Data from Rigid Falling Spheres

Atmospheric density profiles in the stratosphere and mesosphere are determined by means of low cost Global Positioning System (GPS) receivers on in situ rigid falling spheres released from a sounding rocket. Values below an altitude of 80 km are obtained. Aerodynamic drag relates atmospheric densities to other variables such as velocities of spheres, drag coefficients,and reference area.The densities are reconstructed by iterative solution. The calculated density is reasonably accurate, with deviation within 10 % with respect to the European Centre for Medium-range Weather Forecasts ( ECMWF) reference value. The atmospheric temperature and wind profiles are obtained as well, and compared to independent data.

Anomalies of zenith tropospheric delay following the <i>M</i>_w 7.8 Haida Gwaii earthquake

The 2012 Haida Gwaii earthquake was a massive Mw 7.8 earthquake that struck the Queen Carlotte Islands Region on 28 October 2012 (UTC). This study analyzed the variations in zenith tropospheric delay (ZTD) following the Mw 7.8 Haida Gwaii earthquake using near real-time ZTD data collected from eleven stations in the seismic region and the forecast ZTD of ECMWF. A new differential method was used to detect anomalies of ZTD time series. Result showed that obvious ZTD anomalies occurred on the day of the earthquake (day-of-year, doy 302). There were anomalous ZTD variations at eight stations in the post-earthquake period on doy 302, possibly due to the processes of earthquake-generated acoustic waves. Propagation of acoustic waves caused variations of tropospheric parameters (e.g., atmospheric pressure, temperate, and atmosphere density), thus influencing ZTD. Absence of anomalous ZTD variations at the remaining three stations was attributed to the special topographic conditions, i.e., the long epicentral distance and the presence of huge mountains as a natural protective screen. Our work provides new insights to the relationship between of earthquake event and ZTD variation. The proposed differential method is superior to conventional method for detecting specific ZTD anomalies caused by earthquake events.