Non-Linear Constitutive Equations for Transversely Isotropic Materials Belonging to the С∞ and С∞h Symmetry Groups

Transversely isotropic materials feature infinite-order symmetry axes. Depending on which other symmetry elements are found in the material structure, five symmetry groups may be distinguished among transversely isotropic materials. We consider constitutive equations for these materials. These equations connect two symmetric second-order tensors. Two types of constitutive equations describe the properties of these five material groups. We derived constitutive equations for materials belonging to the C∞ and C∞h symmetry groups in the tensor function form. To do this, we used corollaries of Curie's Symmetry Principle. This makes it possible to obtain a fully irreducible form of the tensor function.

Efficient AM Algorithms for Stochastic ML Estimation of DOA

The estimation of direction-of-arrival (DOA) of signals is a basic and important problem in sensor array signal processing. To solve this problem, many algorithms have been proposed, among which the Stochastic Maximum Likelihood (SML) is one of the most concerned algorithms because of its high accuracy of DOA. However, the estimation of SML generally involves the multidimensional nonlinear optimization problem. As a result, its computational complexity is rather high. This paper addresses the issue of reducing computational complexity of SML estimation of DOA based on the Alternating Minimization (AM) algorithm. We have the following two contributions. First using transformation of matrix and properties of spatial projection, we propose an efficient AM (EAM) algorithm by dividing the SML criterion into two components. One depends on a single variable parameter while the other does not. Second when the array is a uniform linear array, we get the irreducible form of the EAM criterion (IAM) using polynomial forms. Simulation results show that both EAM and IAM can reduce the computational complexity of SML estimation greatly, while IAM is the best. Another advantage of IAM is that this algorithm can avoid the numerical instability problem which may happen in AM and EAM algorithms when more than one parameter converges to an identical value.

Irreducible posterolateral dislocation of the knee: a case report

Irreducible posterolateral dislocations of the knee are rare lesions, generally caused by high-energy trauma inducing rotational stress and a posterior and lateral displacement of the tibia.In these conditions, the interposition of abundant soft tissue inside the enlarged medial joint space prevents spontaneous reduction or non-surgical treatment by manipulation of the dislocation. Surgical treatment is therefore compulsory.We report the clinical case of a woman who suffered a subluxation of the knee while jogging. The case we describe is of interest because it shows that even less severe knee dislocations, like this subluxation caused by a low-velocity sports trauma, may present in an irreducible form requiring open surgery. Clinical-instrumental monitoring did not reveal any signs of vascular or nerve injury. Owing to the irreducibility of the lesion we were obliged to perform open surgery in order to free the joint from the interposed muscle tissue and repair medial capsule-ligament lesions. Repair of the damaged cruciate ligaments was deferred to a second stage, but ultimately rendered necessary by the persistence of joint instability and the need to address the patient’s functional needs. In the literature, different one- and two-step surgical options, performed by arthroscopy or arthrotomy, are reported for such related problems.The Authors discuss these various options and examine and discuss their own decision taken during the surgical work-up of this case.

Collective Intentionality, Self-referentiality, and False Beliefs: Some Issues Concerning Institutional Facts

J. R. Searle’s general theory of social and institutional reality, as deployed in some of his recent work (The Construction of Social Reality, 1995; Social Ontology and the Philosophy of Society, 1998}, raises many deep and interesting problems. Four issues are taken up here: (1) Searle’s claim to the effect that collective intentionality is a primitive, irreducible form of intentionality; (2) his account of one of the most puzzling features of institutional concepts, their having a self-referential component; (3) the question as to the point, or points, of having institutions; (4) Searle's claim to the effect that false beliefs on the part of the members of the relevant community are compatible with the existence of related institutional facts. It is argued that, under all four respects, Searle's theory proves to be hardly satisfactory.