Covering a bounded set of functions by an increasing chain of slaloms

A slalom is a sequence of finite sets of length omega. Slaloms are ordered by coordinatewise inclusion with finitely many exceptions. Improving earlier results of Mildenberger, Shelah and Tsaban, we prove consistency results concerning existence and non-existence of an increasing sequence of a certain type of slaloms which covers a bounded set of functions in the Baire space

Blurred Borders: Trans-Boundary Impacts & Solutions in the San Diego-Tijuana Border Region

Over the years, the border has divided the people of San Diego County and Tijuana over language, culture, national security, public safety and a host of other cross-border issues ranging from human migration to the environment. For some, the 'us' versus 'them' mentality has become more pervasive following the tragedy of September 11, 2001, with a growing number of San Diegans focusing greater attention on terrorism and homeland security, as well as the need to re-think immigration policy in the United States as a means of fortifying the international border. This is validated by a recent KPBS/Competitive Edge research poll that found 46% of English-speaking San Diegans desiring that the U.S. impose tighter restrictions on the border. Yet the question remains: if San Diegans and Tijuana are so different, why is our shared port of entry the most busily crossed international border in the world with over 56 million crossings a year? The answer is simple. Opposites attract. The contrasts and complementarities between San Diego and Tijuana are so powerful that residents, as well as visiting tourists and business people, endure post-9/11 traffic and pedestrian delays to cross the border for work, school, cultural enrichment, maintaining family ties or sheer economic necessity

STUDY OF J/PSI THREE-BODY DECAYS INVOLVING BARYONS

The $J/\Psi$ decay into a baryon pair and a pseudoscalar meson is computed, for some channels, in lowest order in perturbative QCD, modeling the baryon with a quark-diquark system. We use a set of parameters that has been proposed by some authors in order to fit the proton magnetic form factor $G^{p}_{M}$, the angular distribution of protons in the process $\gamma \gamma \to p \bar{p}$ and the width of $\eta_{c} \to \gamma \gamma$.Comment: Plain Latex file, 10 pages; 1 figure appended as a uuencoded file; Keywords : Charmonium, Baryons, Paiar production, Particle Structure

Pcf theory and cardinal invariants of the reals

The additivity spectrum ADD(I) of an ideal I is the set of all regular cardinals kappa such that there is an increasing chain {A_alpha:alpha<kappa\} in the ideal I such that the union of the chain is not in I. We investigate which set A of regular cardinals can be the additivity spectrum of certain ideals. Assume that I=B or I=N, where B denotes the sigma-ideal generated by the compact subsets of the Baire space omega^omega, and N is the ideal of the null sets. For countable sets we give a full characterization of the additivity spectrum of I: a non-empty countable set A of uncountable regular cardinals can be ADD(I) in some c.c.c generic extension iff A=pcf(A).Comment: 9 page

Design of Flight Control Systems for a Hypersonic Aircraft Using sliding-PID Control

The paper presents the application of sliding-PID control to the design of robust flight control system for a hypersonic aircraft. The proposed controller uses an approach that combines the high-order PID controller with high-order sliding mode (HOSM) control. The PID uses high-order time-derivative (HOTD) function of the sliding mode variable while the HOSM uses the signum function of the HOTD function. HOTD is built using the relative degree nonlinear dynamics of multivariable systems driven by affine control inputs. A displacement autopilot is designed for pitch control of an air-breathing hypersonic vehicle model. Numerical simulation demonstrates the effectiveness of the proposed controller and shows its advantages as compared to the quasi-homogenous HOSM controller

Numerical Assessment of the Thermomechanical Properties of the NiTi Shape Memory Alloy

The paper presents a numerical assessment and characterization of Shape Memory Alloys (SMAs) thermomechanical behavior using an internal variable approach-based constitutive law. A simulation study is conducted to reveal the influence of the key intrinsic properties such as shape memory effect, pseudoelastic effect, hysteresis loop, and non-constant material functions on the loading capacity and thermal actuation of SMAs. The effects of initial conditions, residual strains, and high temperatures on the behavior of SMAs are studied through several thermomechanical loading-unloading scenarios. The results give useful indications on the capability of SMA materials to fully recover large strains under thermal activation, to change their properties reversibly through phase transformation, and to serve as actuator systems for engineering control applications

Single-Rotor Helicopter Dynamics and Maneuvering Simulation

This paper presents the development and validation of a robust flight dynamics model for simulation of a full-scale single-rotor helicopter dynamics and maneuvering. A minimum-complexity dynamic model is used to compute the aerodynamic forces and moments using trajectory-planning strategy. A high-order sliding mode (HOSM) observer is used as a numerical differentiator for computing time rate changes of longitudinal and lateral control inputs to the main rotor dynamics during maneuvering. The HOSM differentiator suppresses numerical instability and increases computation accuracy of both dynamic and kinematic characteristics. Using available data and flight test results for UH-60 helicopter, the control input characteristics are interpolated versus flight speeds. A pull-up maneuver is simulated to demonstrate the effectiveness of the proposed model