The Steiglitz-McBride identification algorithm revisited--Convergence analysis and accuracy aspects

The convergence and accuracy properties of the Steiglitz and McBride identification method are examined. The analysis is valid for a sufficiently large number of data. It is shown that the method can converge to the true parameter vector only when the additive output noise is white. In that case the method is proved to be locally convergent to the true parameters. The global convergence properties are also investigated. It is pointed out that the method is not always globally convergent. Some sufficient conditions guaranteeing global convergence are given. Assuming convergence takes place the estimates are shown to be asymptotically Gaussian distributed. An explicit expression is given for their asymptotic covariance matrix.     

A new nonpenetrating ballistic injury

A new, nonpenetrating ballistic injury mechanism involving individuals protected by soft body armor is described. Experimental studies using laboratory animals have demonstrated that despite stopping missile penetration, the heart, liver, spleen, and spinal cord are vulnerable to injury. The rapid jolting force of an impacting bullet is contrasted with the usually encountered mechanisms producing blunt trauma injury. The experimental methodology used to assess a 20% increase in survival probability and an 80% decrease in the need for surgical intervention with a new soft body armor is reviewed. Five cases of ballistic assaults on law enforcement personnel protected by soft body armor are presented. Four emphasize the potentially lifesaving qualities of the armor, while the fifth indicates the need for torso encircling design. Hospitalization should follow all assaults, regardless of the innocuous appearance of the skin lesion and the apparent well being on the assaulted individual. Therapeutic guidelines for patient management are suggested.     

Identifiability conditions for linear multivariable systems operating under feedback

The possibility of estimating the parameters of a dynamic system when it is operating in closed loop is examined. Earlier considered ways of designing regulators to achieve desired identifiability properties are unified and generalized. The result of the analysis of this short paper gives a simple criterion, which contains earlier known conditions as simple special cases.     

Light trapping with titanium dioxide diffraction gratings fabricated by nanoimprinting

Dielectric scattering structures are a promising way of trapping light in solar cells. Titanium dioxide is a particularly attractive candidate material because of its high refractive index and ability to be deposited on a finished solar cell. Here, we present an experimental demonstration of photocurrent enhancement in thin film recrystallised silicon solar cells using TiO₂ pillar arrays fabricated on the rear of the cells using nanoimprint lithography. A short circuit current enhancement of 19% is measured experimentally, and excellent agreement with numerical simulations is obtained. We show numerically that by replacing the Ag capping present on the cells with a detached rear Ag back reflector, the enhancement could reach 37%. Copyright © 2012 John Wiley & Sons, Ltd.     

Helmet use, patterns of injury, medical outcome, and costs among motorcycle drivers in Maryland.

A comprehensive study was conducted of all motorcycle traffic crashes occurring in Maryland during a one-year period. All available medical and cost data were linked with police crash reports. During the study period, 1,900 motorcycle drivers were involved in crashes. The data indicated that (i) helmet usage was 35% overall, 30% among fatally injured drivers, and only 16% among drivers with a history of drug/alcohol conviction, (ii) unhelmeted drivers seen at an emergency department were almost twice as likely to have sustained head injury (40%) as were helmeted drivers (21%) (the corresponding percentages for hospitalized drivers were 55% and 38%), and (iii) acute care cost for unhelmeted drivers was three times ($30,365) that of helmeted drivers.     

Optimal instrumental variable estimates of the AR parameters of an ARMA process

The modified Yule-Walker (MYW) equations for estimating the AR parameters of an ARMA process are presented as a special case of an instrumental variable (IV) method. The consistency and accuracy of the AR parameter estimates are studied. It is shown that estimation accuracy increases monotonically with the number of MYW equations for an optimal choice of the weighting matrix used in the least-squares solution of these equations. The asymptotic error covariance of the optimal IV method equals that of the prediction error method. The results of this paper verify experimental results reported in the literature regarding the performance of the MYW method, and provide the necessary accuracy analysis. Furthermore, they suggest several simple, asymptotically efficient, multistep algorithms for estimating the AR parameters, which are presented in a companion paper.     

A multiple-state memory cell based on the resonant tunneling diode

The device consists primarily of several molecular-beam-epitaxy (MBE-) grown GaAs/(AlGa)As resonant tunneling diodes connected in parallel. This device exhibits multiple peaks in the I-V characteristic. When a load resistor is connected, the circuit can be operated in a multiple stable mode. With this concept, implementation of three-state and four-state memory cells are made. In the three-state case the operating points at voltages V₀=0.27 V , V₁=0.42 V, and V₂=0.53 V represent the logic levels 0, 1, and 2. Similarly for the four-state memory cell the logic levels voltages are V₀=0.35 V, V₁=0.42 V, V₂=0.54 V, and V ₃=0.59 V. A suggestion of an integrated device structure using this concept is also presented     

The application of nonlinear dynamic data reconciliation to plant data

We have extended a fairly comprehensive data reconciliation approach called nonlinear dynamic data reconciliation (NDDR) that was originally presented by Liebman et al. (1994, Comput. Chem. Engng, 16, 963–986). This approach is capable of reconciling data from both steady-state and dynamic processes as well as estimating parameters and unmeasured process variables. One recently added feature is the ability to detect measurement bias. Each of these features were developed and tested using computer simulation. In this paper we report the successful application of NDDR to reconcile actual plant data from an Exxon Chemicals process.