A Layered Boundary Element Nonlinear Analysis of Beams

This work aims to introduce a new layered approach to the nonlinear analysis of initially straight Euler-Bernoulli beams by the Boundary Element Method (BEM). The beam is studied in the context of both geometrical and material nonlinearity. The governing differential equations, derived by applying the principle of minimum total potential energy, are coupled and nonlinear, while the boundary conditions are the most general and may include elastic support or restraint. The boundary value problem, regarding the axial and transverse displacements, is solved using the Analog Equation Method (AEM), a BEM based method, together with an iterative procedure. Although a direct solution to the geometrical nonlinear problem has already been presented, in this work an alternative layered analysis is proposed. The discretization is applied in both the longitudinal direction and the cross-sectional plane, and an iterative process is commenced. First, initial fictitious load distributions are assumed at beam's each cross-section, and the displacements, as well as their derivatives, are computed using the AEM. Second, the two stress resultants, i.e., the axial force and bending moment, are evaluated by appropriate integration over the cross-section. In the end, the derivatives of the stress resultants are evaluated, and the equilibrium of the governing equations is checked. If the equilibrium is satisfied, the process is terminated. Otherwise, the fictitious load distributions are updated, and the procedure starts over again. Several representative examples are studied, and the results are compared with those presented in the literature, validating the reliability and effectiveness of the proposed method

Earthquake response of hysteretic mass-column using non-Gaussian closure

A non-Gaussian closure scheme based on the Edgeworth expansion of the probability density function is used to study the response of a hysteretic structure under random parametric excitation. The system considered consists of a weightless mass supporting a concentrated mass and it is subjected to the vertical and horizontal components of the ground acceleration modeled as nonstationary Gaussian white noise processes. The material of the structure exhibits bilinear hysteretic behaviour. The equation governing the motion of the system is transformed into an Itô stochastic differential equation. A set of ordinary differential equations governing the response statistics are obtained. These form an infinite hierarchy of equations which must be truncated in order to solve for moments of any order. The Edgeworth expansion of the joint density is used to truncate this infinite hierarchy. Such a closure scheme appears desirable since for hysteretic systems an explicit expression of the probability density is required. A frequently used closure scheme based on Gaussian assumption underestimates the response. The non-Gaussian density can be used in reliability studies. © 1991

Future perspectives in cancer immunotherapy

The advent of immunotherapy has transformed the treatment paradigm of several solid tumors and is expected to influence the therapeutic algorithm even more in the future following the results of numerous ongoing clinical trials in a wide range of malignancies. Exploiting the anti-cancer effect of the immune system with the use of vaccines, viral vectors, and more lately with immune check-point inhibitors and chimeric antigen receptor modification, has been proven a successful therapeutic strategy in a broad spectrum of tumors. In particular, immune check-point inhibition in melanoma, non-small-cell lung cancer and renal cancer, peptide vaccination in prostate cancer and glioblastoma, and oncolytic immunotherapy in melanoma are well-established therapeutic modalities that have obtained approval by regulatory authorities and are already in clinical use. A large number of ongoing clinical trials involving thousands of patients are currently seeking to define the appropriate tumor type, therapeutic setting, treatment combination and patient populations in order to maximize clinical benefit from immunotherapeutic agents. In this context, identification of the patients whose tumors are most likely to respond to immunotherapy by the use of appropriate biomarkers will be crucial for the optimal implementation of immunotherapy into the therapeutic armamentarium

Performance indicators for offshore wind farms

The drive for alternative energy sources has resulted in many proposals for offshore wind farms in the United Sates. Offshore wind turbines are subject to harsh environmental conditions including but not limited to simultaneous action of extreme wind and wave loading as well as hurricanes. From a structural reliability point of view, there are several failure mechanisms of a wind turbine such as blade or other component fatigue, tower local or global buckling and foundation failure such as sliding. In addition, there are several mechanical components and a control mechanism that could be studied from a traditional reliability point of view. Given the complexity of the problem which involves a combination of structural and electromechanical systems, an approach based on annual power generation is considered here to evaluate the performance of offshore wind farms. © ASCE 2011