Development of a high frequency ultrasonic setup for measuring the parameters of thin films

In this report a novel method for measuring the elastic properties of thin 10 nm films is described. The method is based on the use of a nanosecond laser for generation acoustic waves in solids. Absorption of the incident laser pulse energy and the associated temperature gradients induces a rapidly changing strain field. This strain field, in turn, radiates energy as elastic (ultrasonic) waves. At low pulse power, this is an entirely thermo elastic process resulting in no damage to the sample. The acoustic echo arriving at the probed surface causes both the displacement of the surface (a few nanometres) and the strain in the subsurface material, which might be detected through the variation of the optical reflectivity of the material, i.e. through the acousto-optic effect.

Photothermoelastic Interactions in Silicon Microbeams Resting on Linear Pasternak Foundation Based on DPL Model

In this work, the photothermal interactions in semiconductor microbeams during the photo-thermo-elastic process have been investigated using the generalized photothermal theory. The proposed mathematical model is constructed based on the Euler–Bernoulli model, the heat equation with two-phase lag and coupled plasma wave equation that indicates the prediction of thermal, elastic and photovoltaic effects in the microbeam resonators. Based on the introduced model, the dynamic influence of thermoelastic photovoltaic microbeam resting on an elastic foundation medium with two parameters has been studied. The Winkler foundation parameter is one of these parameters while the second is the shear foundation parameter. In the field of Laplace transform, the governing equations have been solved while the inverse transforms are found numerically using a tried-and-true approximation technique based on Fourier transform series. The numerical calculations of thermophysical field variables have been discussed and graphically presented. The effects of the magnetic field, Winkler and shear foundation parameters, and lifetime of photogenerated electron have been investigated and studied in detail. Comparisons have been made between the proposed model and previous models that have been derived as special cases from the presented results.

Modeling Peer Selection and Influence in Youth Social Networks: A Case Study for U.S. Marine Corps Recruiting and Training

Youth currently entering the job market are part of Generation Z. Research suggests that this generation is different from others in their values and life priorities and will challenge organizations who wish to attract, develop, and retain its members while ensuring the same level of operations. We present a simulation-based approach to understanding how peer selection and peer influence drive the spread of behaviors, values, and beliefs through social networks of youths, and how organizations can use influence pathways in such networks to recruit and develop their personnel. We illustrate our approach on a case study of United States Marine Corps (USMC) recruiting and training. We detail the logic and theoretical underpinnings of our model and describe how it allows to understand the driving forces of generational changes in the young American population and how they might be addressed. We show that while peer influence with respect to relevant Marines' traits is a highly elastic process, peer selection is rooted in deep-seated, slowly changing individual perceptions. We further show that peer influence is confined to intimate networks, making intervention difficult. Finally, we discuss recommendations for Marine Corps training and recruiting approaches as implied by the findings from our model.

Biology of NSCLC: Interplay between Cancer Cells, Radiation and Tumor Immune Microenvironment

The overall prognosis and survival of non-small cell lung cancer (NSCLC) patients remain poor. The immune system plays an integral role in driving tumor control, tumor progression, and overall survival of NSCLC patients. While the tumor cells possess many ways to escape the immune system, conventional radiotherapy (RT) approaches, which are directly cytotoxic to tumors, can further add additional immune suppression to the tumor microenvironment by destroying many of the lymphocytes that circulate within the irradiated tumor environment. Thus, the current immunogenic balance, determined by the tumor- and radiation-inhibitory effects is significantly shifted towards immunosuppression, leading to poor clinical outcomes. However, newer emerging evidence suggests that tumor immunosuppression is an “elastic process” that can be manipulated and converted back into an immunostimulant environment that can actually improve patient outcome. In this review we will discuss the natural immunosuppressive effects of NSCLC cells and conventional RT approaches, and then shift the focus on immunomodulation through novel, emerging immuno- and RT approaches that promise to generate immunostimulatory effects to enhance tumor control and patient outcome. We further describe some of the mechanisms by which these newer approaches are thought to be working and set the stage for future trials and additional preclinical work.

Учет влияния полей остаточных деформаций в современных физико-механических технологиях обработки конструкционных материалов

A strict determination of the mechanisms of redistribution of previously accumulated irreversible strains as a result of additional elastic shock actions on the material is given for a nonlinear gradient model of large elastic–plastic strain. It is shown that this redistribution is limited by rigid transport and rotation of the plastic strain tensor. Formulas for a change in the initial components of the plastic strain tensor in elastic waves are derived. It is shown that the preliminary plastic field affects the dynamics of further reversible strain as one of the factors of formation of the initial quasi-static elastic field, which cannot be obtained in a purely elastic process.

A convenient form of the multiplicative decomposition of the deformation gradient

For many purposes in continuum mechanics it has been found useful to decompose the deformation gradient into two factors, which result from some elastic process through which destressing is achieved at a material point. There is an essential rotational non-uniqueness in these factors; however, some subfactors are uniquely defined. In particular, a certain unique right stretch tensor is identified, which serves as a convenient independent variable for describing the anisotropic elastic response of a solid from its evolving stress-free intermediate configurations.

A Study on Photothermal Waves in a Semiconductor Material Photogenerated by a Focused Laser Beam

In this work, the theory of coupled plasma, thermal and elastic waves were used to investigate the wave propagation on semiconductor material during photo-thermo-elastic process. A thin slim strip (TSS) medium, elastic semiconductor with isotropic and homogeneous thermal and elastic properties have been considered. The plasma, thermal and elastic waves in a TSS photo generated by a focused and intensity modulated laser beam were analyzed. Laplace transform techniques and eigenvalue approach were used to obtain the analytical solutions for carrier density, displacement, temperature, and stress. Numerical computations have been carried out on silicon-like semiconductor material. The results are presented graphically to show the effect of the coupling between the plasma, thermal, and elastic waves.