Evaluation of Compacted Cementitious Composites for Porous Bearings

The use of porous materials as a restrictor in aerostatic bearings provides many advantages over conventional restrictors, such as small variation of temperature, high damping, high operational speeds, limited wear, and capacity to support radial, axial, and combined loading. A design of experiment (DOE) was carried out to evaluate cold‐pressed cementitious composites as an air restrictor in thrust bearings. The physical and mechanical properties such as the apparent porosity, permeability, and elastic modulus were investigated in this work, thus verifying the structural and flow characteristics of the composites for such application. The composites fabricated with low compacting pressure and small silica particles provided the material requirements for porous bearings.     

A scale space based algorithm for automated segmentation of single shot tagged MRI of shearing deformation

Object

This study proposes a scale space based algorithm for automated segmentation of single-shot tagged images of modest SNR. Furthermore the algorithm was designed for analysis of discontinuous or shearing types of motion, i.e. segmentation of broken tag patterns.

Materials and methods

The proposed algorithm utilises non-linear scale space for automatic segmentation of single-shot tagged images. The algorithm's ability to automatically segment tagged shearing motion was evaluated in a numerical simulation and in vivo. A typical shearing deformation was simulated in a Shepp-Logan phantom allowing for quantitative evaluation of the algorithm's success rate as a function of both SNR and the amount of deformation. For a qualitative in vivo evaluation tagged images showing deformations in the calf muscles and eye movement in a healthy volunteer were acquired.

Results

Both the numerical simulation and the in vivo tagged data demonstrated the algorithm’s ability for automated segmentation of single-shot tagged MR provided that SNR of the images is above 10 and the amount of deformation does not exceed the tag spacing. The latter constraint can be met by adjusting the tag delay or the tag spacing.

Conclusion

The scale space based algorithm for automatic segmentation of single-shot tagged MR enables the application of tagged MR to complex (shearing) deformation and the processing of datasets with relatively low SNR.     

Calculation and visual displaying of the water chemistry conditions in return cooling systems at thermal power stations

Matters concerned with treatment of cooling water at thermal power stations are addressed. Problems arising during operation of return cooling systems equipped with cooling towers are analyzed. The software used for monitoring, control, and indication of the hydraulic and water chemistry operating conditions of the circulation system at the Yaivinsk district power station is considered.     

Giant Magnetoelectric Effect in Thin‐Film Composites

Highly sensitive AC magnetic field sensors are presented using magnetoelectric composites consisting of magnetostrictive and piezoelectric phases. They are offering passive nature, high sensitivity, large effect enhancement at mechanical resonance, and large linear dynamic range. Thin‐film magnetoelectric 2‐2 composites benefit from perfect coupling between the piezoelectric and magnetostrictive phases and from the reduction in size which is essential for high spatial resolution. Their design uses AlN and a plate capacitor or PZT with interdigital electrodes and magnetostrictive amorphous FeCoSiB single layers or exchanged biased multilayers. At mechanical resonance and depending on the geometry, extremely high ME coefficients of up to 9.7 kV/cm Oe in air and up to 19 kV/cm Oe under vacuum were obtained. To avoid external DC magnetic bias fields, composites consisting of exchanged biased multilayers serving as the magnetostrictive component with a maximum magnetoelectric coefficient at zero magnetic bias field are employed. Furthermore, the anisotropic response of these exchanged biased composites can be utilized for three‐dimensional vector field sensing. Sensitivity and noise of the sensors revealed limits of detection as good as to 2.3 pT/Hz^1/2 at mechanical resonance. Sensitivity between 0.1 and 1000 Hz outside resonance can be enhanced through frequency conversion using AC magnetic bias fields.     

Model of a persistent photodetector for analyzing the threshold sensitivity in the problem of detection of a moving point object

A model of the direction-finding characteristic of a moving point object for a persistent photodetector is proposed. The model ensures the calculation of the direction-finding characteristic as a function of photodetector parameters and object velocity, which form the basis for calculating the probability of detection of moving point objects. Results of numerical experiments are reported.     

SOI nanowire transistor for detection of D-NFATc1 molecules

Nanowire (NW) detection is one of the fast and highly sensitive methods. An NW biosensor based on silicon-on-insulator (SOI) structures are used in the reported study for real-time label-free biospecific detection of the NFATc1 (D-NFATc1) cancer marker. For this purpose, the SOI NWs are functionalized with NFATc1 aptamers used as macromolecular probes. It is demonstrated that such a biosensor can ensure a detection limits up to 10^?15 M, which is comparable with the sensitivity ensured by an NW biosensor with immobilized antibodies used as macromolecular probes. The results of this study demonstrate that such approaches to the development of sensor elements for highly sensitive diagnostics of diseases are really promising.     

Development of a practical Monte Carlo based fuel management system for the Penn State University Breazeale Research Reactor (PSBR)

A practical fuel management system for the he Pennsylvania State University Breazeale Research Reactor (PSBR) based on the advanced Monte Carlo methodology was developed from the existing fuel management tool in this research. Several modeling improvements were implemented to the old system. The improved fuel management system can now utilize the burnup dependent cross section libraries generated specifically for PSBR fuel and it is also able to update the cross sections of these libraries by the Monte Carlo calculation automatically. Considerations were given to balance the computation time and the accuracy of the cross section update. Thus, certain types of a limited number of isotopes, which are considered “important”, are calculated and updated by the scheme. Moreover, the depletion algorithm of the existing fuel management tool was replaced from the predictor only to the predictor-corrector depletion scheme to account for burnup spectrum changes during the burnup step more accurately. An intermediate verification of the fuel management system was performed to assess the correctness of the newly implemented schemes against HELIOS. It was found that the agreement of both codes is good when the same energy released per fission (Q values) is used. Furthermore, to be able to model the reactor at various temperatures, the fuel management tool is able to utilize automatically the continuous cross sections generated at different temperatures. Other additional useful capabilities were also added to the fuel management tool to make it easy to use and be practical. As part of the development, a hybrid nodal diffusion/Monte Carlo calculation was devised to speed up the Monte Carlo calculation by providing more converged initial source distribution for the Monte Carlo calculation from the nodal diffusion calculation. Finally, the fuel management system was validated against the measured data using several actual PSBR core loadings. The agreement of the predicted core excess reactivities and the measured values is found to be good considering the measurement uncertainties.     

On the formation of the structure of a carburized layer during cementation of a low-carbon martensitic steel 12Kh2G2NMFT

The process of production and subsequent strengthening of a gradient carburized layer on a low-carbon martensitic steel 12Kh2G2NMFT has been investigated. It has been shown that the structure and properties of the carburized layer and of the base of the steel can be optimized by quenching from the intercritical temperature range after a preheating or high-temperature tempering. In the carburized layer, reverted austenite with a high hardness equal to or even exceeding the hardness of martensite has been obtained. The strengthening of the austenite occurs due to the precipitation of dispersed carbides during heat treatment following cementation.     

On one new modification of Alekseevskii-Tate model for nonstationary penetration of long rods into targets

New ballistics equations for long rods penetrating both elastic-plastic and brittle materials are proposed which generalize the well-known Alekseevskii-Tate equations. These equations are derived from the basis of the Lagrange-Cauchy integral for equations of nonstationary irrotational motion of ideal fluids, as well as the equations of the dynamics of expansion of a spherical cavity. Their solutions determine both the translational movement of the penetrator and the dynamics of cavity formation in the target. The structure of the equations is sufficiently simple for analysis and solution. The calculations demonstrate good qualitative agreement of the theoretical predictions with the experimental data.     

A discharge with runaway electrons: Efficient process for the formation of Rydberg states in oxygen molecules

A new method for exciting high-lying states in oxygen molecules is proposed, which is based on the interaction of O₂ molecules with a low-energy (～10²–10⁴ eV) electron beam formed in a discharge with runaway electrons. An algorithm for calculating the electron energy distribution function (EEDF) using the Monte Carlo simulation technique is developed. The EEDF calculation for a discharge in pure oxygen is performed for a plasma pumped with monoenergetic electron beam in the absence of an external electric field. Efficiencies of the formation of Rydberg and Herzberg states in oxygen molecules under conditions of a quasi-stationary dc discharge and a discharge with runaway electrons are compared.