Uniquely identifiable state-space and ARMA parametrizations for multivariable linear systems

Multivariable systems can be represented, in a uniquely identifiable way, either by canonical forms or by so-called overlapping forms. The advantage of the latter is that they do not require the a priori estimation of a set of structural invariants (e.g. Kronecker invariants). We show here how to define uniquely identifiable overlapping parametrizations for state-space and ARMA models. We show that these parametrizations are all related to a set of intrinsic invariants, which are obtained from the Markov parameters of the system. Different forms of overlapping ARMA parametrizations are derived and their properties discussed.     

Mutual information for the selection of relevant variables in spectrometric nonlinear modelling

Data from spectrophotometers form vectors of a large number of exploitable variables. Building quantitative models using these variables most often requires using a smaller set of variables than the initial one. Indeed, a too large number of input variables to a model results in a too large number of parameters, leading to overfitting and poor generalization abilities. In this paper, we suggest the use of the mutual information measure to select variables from the initial set. The mutual information measures the information content in input variables with respect to the model output, without making any assumption on the model that will be used; it is thus suitable for nonlinear modelling. In addition, it leads to the selection of variables among the initial set, and not to linear or nonlinear combinations of them. Without decreasing the model performances compared to other variable projection methods, it allows therefore a greater interpretability of the results.     

Reliability test methods for media-compatible pressure sensors

Two applications of media exposure testing of pressure sensors with barrier coatings are presented. Experimentation was performed on an apparatus that was developed specifically for the exposure of these devices with in situ output voltage measurement in organic or aqueous environments. The first example illustrates the swelling of fluorosilicone gels in fuels and establishes a solubility parameter for one fluorosilicone gel between 6-8 (cal/cm³)^1/2. While exposure to organic solutions has not been observed to cause catastrophic failure of fluorosilicone-gel-filled devices, corrosion is accelerated in subsequent aqueous solution exposure. An additional experiment was used to simulate automotive exhaust gases and water by exposing devices to a fuel mixture followed by an acidic solution. The second experiment was performed to study corrosion under parylene coatings during exposure to an alkaline test solution for white-goods applications. Acceleration factor expressions have been estimated considering parylene coating thickness, solution pH, and applied device supply voltage as acceleration means. These expressions have been used to evaluate parylene-coated pressure sensors against a benchmark lifetime requirement. For a 1% failure rate, parylene-coated pressure sensors survived approximately 500 h, whereas an alternative, fluorosilicone gel over parylene C coating survived over 2000 h. Furthermore, these media exposure experiments provided insight into the failure mechanisms and defined acceleration factors     

Transition-metal-free oxidative coupling reactions for the formation of C-C and C-N bonds mediated by TEMPO and its derivatives

The application of nitroxides for the development of new synthetic methods and their implementation in polymer chemistry, material science and beyond is one of the major research topics in our laboratory in the institute of organic chemistry at the WWU Münster. This short review focuses on our recent progress towards nitroxide-based transition-metal-free oxidative coupling reactions. The demand for organic surrogates for transition metals in such transformations is in our eyes unquestionable, since environmental and economic issues have become progressively more important in recent years. For this purpose, the 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO) is shown to be a highly efficient oxidant for the homo- and cross-coupling of Grignard reagents. This powerful C-C bond forming strategy allows the generation of conjugated polymers from bifunctional Grignard reagents. Moreover, cross-coupling of alkynyl Grignard compounds and nitrones can be accomplished under aerobic atmosphere with catalytic amounts of TEMPO. It is also shown that TEMPO-derived N-oxoammonium salts can act as suitable oxidants for formation of C-N bonds between non-preactivated benzoxazoles and secondary amines under metal-free conditions.     

Self-efficacy and marijuana cessation: A construct validity analysis.

Hypotheses regarding the relationships between self-efficacy for avoiding marijuana use and theoretically related measures were examined in a sample of 161 men and 51 women who sought treatment aimed at marijuana cessation. Theoretically proposed sources of efficacy judgments showed stronger univariate and multivariate relationships with efficacy for avoiding marijuana use after treatment than before treatment. The cognitive-behavioral relapse prevention treatment resulted in marginally greater self-efficacy, compared with a nonbehavioral treatment, but the link between coping skill training and efficacy was ambiguous. Efficacy contributed incrementally to the prediction of posttreatment marijuana use beyond efficacy source variables, but it did not completely mediate the effects of those sources of efficacy judgments. Predictive validity was stronger for frequency of posttreatment marijuana use than for abstinence status. The need for better assessment of the efficacy construct and potential revisions in efficacy theory as applied to substance use are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On psychoanalysis and academic psychology.

Comments on the article by G. A. Hornstein (see record 1992-24439-001), which argues that through its long-standing clash with psychoanalysis, academic psychology has benefited and commonalities have emerged. F. J. Wertz maintains that however flexible and broad-based academic psychology may have become because of psychoanalysis, their respective ground rules remain mutually opposed, and it would be wrong to conclude that a deep resolution of differences has been achieved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On a generalized predictive control algorithm

Generalized predictive control algorithms with reference models on imputs and outputs of the process have been proposed recently in the literature. Thise algorithms are extended by introducing suitable weighting factors in the performance index and it is shown that such algorithms provide a combined feedback feedforward control resulting in pole-zero cancellation of poles which do not correspond to the reference model. Hence, the system behaves asymptotically as the reference model provided the cancelled poles are stable. Therefore, a careful analysis of the stability of those poles in still needed.     

Robust stabilization of a nonlinear cement mill model

Plugging is well known to be a major cause of instability in industrial cement mills. A simple nonlinear model able to simulate the plugging phenomenon is presented. It is shown how a nonlinear robust controller can be designed in order to fully prevent the mill from plugging     

Development of gas diffusion layer using water based carbon slurry for proton exchange membrane fuel cells

The micro-porous layer of gas diffusion layers (GDLs) was fabricated with the carbon slurry dispersed in water containing sodium dodecyl sulfate (SDS), by wire rod coating process. The aqueous carbon slurry with micelle-encapsulation was highly consistent and stable without losing any homogeneity even after adding polytetrafluoroethylene (PTFE) binder for hundreds of hours. The surface morphology, contact angle and pore size distribution of the GDLs were examined using SEM, Goniometer and Hg Porosimeter, respectively. GDLs fabricated with various SDS concentrations were assembled into MEAs and evaluated in a single cell PEMFC under diverse operating relative humidity (RH) conditions using H₂/O₂ and H₂/air as reactants. The peak power density of the single cell using the GDLs with optimum SDS concentration was 1400 and 500 mW cm⁻² with H₂/O₂ and H₂/air at 90% RH, respectively. GDLs were also fabricated with isopropyl alcohol (IPA) based carbon slurry for fuel cell performance comparison. It was found that the composition of the carbon slurry, specifically SDS concentration played a critical role in controlling the pore diameter as well as the corresponding pore volumes of the GDLs.     

Predictive validity of cocaine, sedative, and alcohol dependence diagnoses.

This study examined the predictive validity of Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders-III-Revised (DSM-III-R) (R. L. Spitzer et al, 1990) based substance dependence diagnoses (i.e., cocaine, sedative, and alcohol) for 518 opioid-dependent outpatients entering methadone maintenance. Patients were followed over 1 year of treatment, which involved daily methadone substitution supplemented by individual and group counseling. Urine specimens were tested randomly 1–4 times per month. Patients diagnosed with current cocaine, sedative, or alcohol dependence were more likely to use these drugs than were patients with past only or no dependence syndrome. Current cocaine dependence predicted early treatment dropout. The results demonstrate the predictive and discriminant validity of several substance dependence diagnoses common among patients in substance abuse or other psychiatric treatment settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)