Photochlorination of Stearic Acid Adsorbed on Alumina

Stearic acid adsorbed on alumina as a dense monomolecular layer was photochlorinated in the dry solid state. The results show that over 90% of the chlorination was on the ω and ω-1 positions and 8.5% on ω-2. No chlorination was detected on the other positions. This establishes the assumption that in a dense monomolecular layer only the terminal groups are exposed to chemical reaction.     

The all-pass property of optimal open-loop tracking systems

The structure of the optimal open-loop linear model-following system is investigated. It is shown that if the given plant is asymptotically stable but has zeros in the right half-plane, the stable optimal system contains an all-pass network whose transference possesses unity, singular values on the imaginary axis. In the special case of optimal tracking, it is shown that the resulting optimal transfer function matrix of the system is equal to the all-pass transfer function matrix which is normalized to be the identity matrix at the zero frequency.     

Input–output approach to stability and -gain analysis of systems with time-varying delays

Stability and L₂ (l₂)-gain of linear (continuous-time and discrete-time) systems with uncertain bounded time-varying delays are analyzed under the assumption that the nominal delay values are not equal to zero. The delay derivatives (in the continuous-time) are not assumed to be less than q<1. An input–output approach is applied by introducing a new input–output model, which leads to effective frequency domain and time domain criteria. The new method significantly improves the existing results for delays with derivatives not greater than 1, which were treated in the past as fast-varying delays (without any constraints on the delay derivatives). New bounded real lemmas (BRLs) are derived for systems with state and objective vector delays and norm-bounded uncertainties. Numerical examples illustrate the efficiency of the new method.     

Robust H∞ output‐feedback control of retarded state‐multiplicative stochastic systems

Linear, state‐delayed, continuous‐time systems are considered with both stochastic and norm‐bounded deterministic uncertainties in the state–space model. The problem of robust dynamic H_∞ output‐feedback control is solved, for the stationary case, via the input–output approach where the system is replaced by a nonretarded system with additional deterministic norm‐bounded uncertainties. A delay‐dependent result is obtained which involves the solution of a simple linear matrix inequality. In this problem, a cost function is defined which is the expected value of the standard H_∞ performance cost with respect to the stochastic parameters. A practical example taken from the field of guidance control is given that demonstrates the applicability of the theory. Copyright © 2010 John Wiley & Sons, Ltd.     

New conditions for delay-derivative-dependent stability

Two recent Lyapunov-based methods have significantly improved the stability analysis of time-delay systems: the delay-fractioning approach of Gouaisbaut and Peaucelle (2006) for systems with constant delays and the convex analysis of systems with time-varying delays of Park and Ko (2007). In this paper we develop a convex optimization approach to stability analysis of linear systems with interval time-varying delay by using the delay partitioning-based Lyapunov–Krasovskii Functionals (LKFs). Novel LKFs are introduced with matrices that depend on the time delays. These functionals allow the derivation of stability conditions that depend on both the upper and lower bounds on delay derivatives.     

Offset reduction in Hall effect measurements using a nonswitching van der Pauw technique

A nonswitching van der Pauw technique, which uses two electrically isolated alternating current sources operating at two different frequencies and two lock-in amplifiers, is suggested for Hall effect measurements. Parasitic offset voltage, typical for this type of measurements, is reduced by averaging two sets of data accumulated simultaneously. Application of the technique is particularly useful when the offset changes on a time scale comparable to the measurement cycle.     

Positive illusions about marriage among married and single individuals.

The common tendency to describe one's marriage in unrealistic terms has been conceptualized as a positive illusion about marriage. Studies of positive illusions have relied on the logical argument that these perceptions are unreasonably positive. This reasoning is insufficient, because previous studies have relied on volunteer samples with high marital satisfaction and long marital duration, both of which could explain rosy evaluations of one's marriage. The current series of studies examined whether positive marital illusions are an artifact of marital satisfaction and duration. Married and single individuals' estimates of their divorce likelihood and other measures of positive marital illusions revealed that illusions about marriage are not dependent on a volunteer bias, marital satisfaction, or duration. The presence of illusions about a future marriage among single individuals suggests that positive marital illusions are a cultural phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Frequency effects in a pancake coil

An aluminum pancake coil is designed to amplify pulsed power in the range of 100-MW to a 100-mΩ electro-thermal load. For the tradeoff between the coil energy density limit and energy discharge efficiency, the frequency dependence of its current and magnetic field distributions is calculated in the range of DC to 1 kHz. Near DC magnetic field measurements are compared to the calculated results. Energy efficiency of about 85% has been measured for the discharge of 1.6 kA from the coil to a linear resistive load in the range of 40-400 mΩ