GEODESY, CARTOGRAPHY AND AERIAL PHOTOGRAPHY

The aim of this work is to evaluate the accuracy of determining the wet component of zenith tropospheric delay (ZTD) from GNSS-measurements and the accuracy of determining the hydrostatic component according to the Saastamoinen model in comparison with the radio sounding data as well. Zenith tropospheric delay is determined mainly by two methods - traditional, using radio sounding or using atmospheric models, such as the Saastamoinen model, and the method of GNSS measurements. Determination of the hydrostatic component of the zenith tropospheric delay was performed by radio sounding data obtained at the aerological station Praha-Libus in 2011-2013 and in 2018. Data were processed for the middle decades of January and July of each year at 0h o’clock of the Universal Time. The wet component was calculated from GNSS observations. By a significant number of radio soundings at the Praha-Libus aerological station, hydrostatic and wet components of zenith tropospheric delay (ZTD) and the same number of ZTD values derived for the corresponding time intervals from GNSS measurements at the GOPE reference station were determined. The values of the wet component of ZTD were determined and compared with the corresponding data obtained from radio soundings. We found that the error of the hydrostatic component in winter does not exceed 10 mm in absolute value, and in summer it is approximately 1.5 times smaller. This is due to differences in the stratification of the troposphere and lower stratosphere in winter and summer. As for the wet component of ZTD, its errors do not exceed: in winter 15 mm, in summer – 35 mm. The resulting differences in summer have a negative sign, indicating a systematic shift, and in winter – both negative and positive. Today, there are many studies aimed at improving the accuracy of determining zenith tropospheric delay by both Ukrainian and foreign authors, but the problem of the accuracy of the hydrostatic component remains open. The study provides recommendations for further research to improve the accuracy of zenith tropospheric delay.

Approximate analysis of quadrilateral slabs having various cases of boundary conditions and aspect ratios

This paper provides an approximate analysis of quadrilateral slabs having various cases of aspect ratios and boundary conditions based on actual two-way action. Nine slabs with different boundary conditions, each having 11 aspect ratios were analyzed using SAP2000 software, thereafter, robustly validated against mathematical solutions. In this article, the hydrostatic point phenomenon was established as a reference point for identifying the slabs with actual two-way action and as a growth reference for other cases. This allows for the use of growth models for the hydrostatic and deviatoric moment tensors. The innovative selection of the extreme positive point moment facilitates the introduction of materials nonlinearity into the design. The plate shorter dimension was used for moment normalization in both directions to preserve the directional influence of the dimensions and to isolate the hydrostatic phenomenon. Through starting at a point of hydrostatic phenomenon occurrence and via fixing one of the plate’s dimensions and extending the other (for any boundary conditions), the extreme point’s Mohr circle develops from the hydrostatic point phenomenon as a growth in the hydrostatic component and drastic growth in the deviatoric component. Subsequently, the largest principal moment develops a higher magnitude as the aspect ratio increases. Furthermore, the non-identical boundary conditions on two perpendicular directions result in a deviation of the two-way action.

Interfacial Fracture Strength of Viscoelastic Inclusions in a Polymer Blend

The interfacial fracture strength in polymer blends is investigated in this study. The constitutive relations of polymeric matrix and inclusions are both approximately described by linear viscoelastic models. It is assumed that the interfacial de-boding between inclusions and matrix is dominantly induced by the hydrostatic component of remote stress. Based on the assumption, the interfacial de-bonding of a viscoelastic inclusion embedded in an infinite polymeric matrix is analyzed. It is found that the size of inclusion will strongly affect the magnitude of critical stress, and the effect of Poisson’s ratio on the de-bonding is so small that can be ignored.

Calibration of Laser Piezospectroscopy Using Alumina/Chromia Solid Solutions Obtained by Coprecipitation

Cr3+ photoluminescence peizo-spectroscopy (CPLPS) is a technique that allows the measurement of the hydrostatic component of stress in α alumina oxides. This method is being developed in our laboratory as a non-destructive inspection technique for thermal barrier coating systems. It has been shown that the Cr3+ concentration influences the magnitude of the shifts in the fluorescence frequencies, Δv of the R1 and the R2 peaks [1,2] and hence the apparent stress. Therefore, this work is an attempt to quantify the extent of this shift, consequent to the Cr3+ concentration in the TBC systems and to study the variation of this effect with thermal cycles on the TBCs. In addition, we have developed a method of estimating Cr3+ content based on the intensity of satellite peaks referred to as n-lines. The experiments are also designed to validate the n-line based method of estimating Cr3+ content and its affect on the apparent stress value.

An atomic simulation of the influence of hydrogen on the fracture behavior of nickel

A model exploring the effect of the presence of a single hydrogen interstitial on the crack tip configuration of nickel is described. The model is based on a EAM-type potential developed by Daw, Baskes, Bisson, and Wolfer for describing the Ni–Ni, Ni–H, and H–H interactions, and involves the crack tip region of a semi-infinite crack in an infinite solid. Several types of interactions are observed to occur. In a model oriented such that dislocation emission is difficult, hydrogen is observed to increase the crack tip opening displacement (CTOD), exert a force on the crack tip due to interaction between the dilatancy of the defect and the hydrostatic component of the field of the crack, and increase the local tensile stresses. However, the largest contribution to extending the crack derives from the energy released when a hydrogen interstitial escapes to the crack surface. A hydrogen interstitial is also observed to assist dislocation emission in models with an easy emission orientation.

A New Workability Criterion for Ductile Metals

The forming limit curves are important aids in determining the extent of deformation a material can be subjected to during a forming process. In this paper a forming limit criterion for bulk metalworking processes, based on the magnitude of the hydrostatic component and the effective stress of the state of stress, is proposed. The determination of the forming limit curve by means of three simple tests, namely, tension, compression, and torsion tests, is presented.

The Measurement of Stresses in Composites

Although there is mounting interest in the measurement of stresses in composite materials after fabrication and/or use, few measurements to date have not taken into account the three dimensional nature of the stress system in such materials. Most data give only the net stress, that is, the difference between principal stresses. A procedure for a more complete measurement (in a reasonable time) is developed here, including the separation of macrostresses and microstresses. If time does not permit a full investigation, measurements of the lattice parameters of the component phases provide a simple way to sample the hydrostatic component due to differential thermal contraction. The Barrett-Predecki method of adding filler is particularly promising for stress measurements in those composites whose component phases do not give appropriate diffraction peaks. This procedure could also be used for monitoring stresses during the useful life of such materials.

Analysis of Face Seals With Shrouded Pockets

The paper offers an analysis of face seals, using incompressible fluids, aimed at arriving at a quantitative basis for the design and optimization of seals. To improve its hydrodynamic and dynamic capabilities, the parallel face seal is provided with pockets pressurized by the sealed fluid, and shrouded at both the inner and outer peripheries. The relevant Poisson equation is solved for its hydrodynamic, hydrostatic, and squeeze-film components. A parametric study of various geometric permutations and operating conditions is then obtained from the computerized solutions. The results show that the contribution of the hydrostatic forces to stiffness is insignificant, and that both K3 and W3 can be ignored in the optimization of seal dimensions. For high seal pressures, the dominant force and leakage are geared to the hydrostatic component, whereas for low seal pressures, both the hydrodynamic and squeeze-film effects are important.