Meeting the challenges of modern interceptor guidance by non-conventional approaches
The challenge of intercepting threats with non conventional warheads, the major drive for the development of ballistic missile defense systems since the first Gulf War of 1991, became even more serious when the reentry vehicles were assumed to be capable of maneuvering. Successful interception of such targets, requiring very small miss distances, cannot be guaranteed by the classical guidance and estimation methods that have been used against manned aircraft. Future interceptor guidance strategy has to be based on pursuit-evasion game concepts and the estimator design has to be integrated with the guidance law. Following such non conventional approaches has the potential to achieve the requirement of hit-to-kill accuracy against randomly maneuvering threats.
DIFFERENTIAL GAME GUIDANCE LAWS FOR INTERCEPT MISSILES
Guidance laws for intercept missiles are derived using zero-sum, perfect-information differential game theory and optimal control theory. The differential game laws are derived using both a linear constant coefficient missile model and a time varying linear model, which uses an open loop profile of the missile speed. The optimal control law is derived only using the variable velocity missile model. A series of six-degree-of-freedom simulations were used to compare missile performance for these three guidance laws. The results show that both differential game laws result in equivalent missile performance. The differential game laws, in turn, perform slightly better than the optimal control law. I. Introduction Intercept missile guidance laws derived using optimal control theory require an assumption on future action by the target in order to generate the optimal control for that specific projected target action. The feedback characteristic of missile guidance laws allows the missile to compensate for incorrect target action assumptions. In contrast, intercept missile guidance laws derived using zero-sum perfect information differential game theory do not require any assumptions on future target actions. Instead the controls are based on the lateral acceleration maneuver capabilities of the target relative to the missile.
The role of prolactin in andrology: what is new?
Prolactin (PRL) has been long deemed as a hormone involved only in female reproduction. However, PRL is a surprising hormone and, since its identification in the 1970s, its attributed functions have greatly increased. However, its specific role in male health is still widely unknown. Recently, low PRL has been associated with reduced ejaculate and seminal vesicle volume in infertile subjects. In addition, in men consulting for sexual dysfunction, hypoprolactinemia has been associated with erectile dysfunction and premature ejaculation, findings further confirmed in the general European population and infertile men. Several metabolic derangements, recapitulating metabolic syndrome, have also been associated with low PRL both in men with sexual dysfunction and from the general European population. In men with sexual dysfunction, followed-up for more than 4 years, low PRL was identified as an independent predictor of the incidence of major adverse cardiovascular events. Finally, an association with anxiety or depressive symptoms has been found in men with sexual dysfunction and from the general European population. While a direct role for impaired PRL function in the pathogenesis of these reproductive, sexual, metabolic and psychological disorders is conceivable, the possibility that low PRL is a mirror of an increased dopaminergic or a decreased serotonergic tone cannot be ruled-out. Hyperactivity of the dopaminergic system can explain only a few of the aforementioned findings, whereas a hypo-serotonergic tone fits well with the clinical features associated with low PRL, and there is significant evidence supporting the hypothesis that PRL could be a mirror of serotonin in the brain.