Gas sensors for air quality monitoring: realisation and characterisation of undoped and noble metal-doped SnO2 thin sensing films deposited by the pulsed laser ablation

Undoped and noble metal-doped very thin SnO₂ sensing layers deposited by the pulsed laser ablation (PLA) technique upon micromachined Si substrate heater elements have been extensively characterised. The main objective behind the effort carried out in this work has been the challenging perspective to define a sensing layer technology and a sensor operating mode (continuous (DC) vs. pulsed temperature (PT) mode) which allows the long term measuring and the easy discrimination of very low concentration of benzene by an interfering species like carbon monoxide, both present in the outdoor air. The experimental results reported in this work have shown that combining the sensor technology with a suitable catalytic element (in the present case, gold) and a proper sensor operating mode, very low concentration of benzene can be revealed with a sufficient selectivity towards CO. One of the major problems encountered during the long term test of the sensors has been the loss of the sensitivity to benzene with the time. An attempt has been made to explain the reason of this experimental result. We firmly believe that many factors contribute to it. Among them, the annealing of point defects associated with the oxygen vacancies as well as the loss of the catalytic efficiency by the added Au layer as effect of a possible coalescence of the metal clusters at the sensor working temperature (T400°C). To partially reduce the cluster mobility and to preserve the benzene sensitivity, the last assumption would suggest to operate the sensors, no matter if in DC or in PT mode, at a temperature lower than that used in this work.     

Automated CAD conversion with the Machine Drawing UnderstandingSystem: concepts, algorithms, and performance

The Machine Drawing Understanding System (MDUS) is an experimental CAD conversion system aimed at realizing the entire process of understanding mechanical engineering drawings, from scanning to 3D reconstruction. This paper describes the structure, algorithms and current performance of MDUS. The modular structure of the system provides for further improvements and makes it an ideal workbench for researchers wishing to test their own algorithms and incorporate them into the system     

Introducing reactive modal tableaux

This paper introduces the idea of reactive semantics and reactive Beth tableaux for modal logic and quotes some of its applications. The reactive idea is very simple. Given a system with states and the possibility of transitions moving from one state to another, we can naturally imagine a path beginning at an initial state and moving along the path following allowed transitions. If our starting point is s ₀, and the path is s ₀, s ₁,..., s _n , then the system is ordinary non-reactive system if the options available at s _n (i.e., which states t we can go to from s _n ) do not depend on the path s ₀,..., s _n (i.e., do not depend on how we got to s _n ). Otherwise if there is such dependence then the system is reactive. It seems that the simple idea of taking existing systems and turning them reactive in certain ways, has many new applications. The purpose of this paper is to introduce reactive tableaux in particular and illustrate and present some of the applications of reactivity in general. Mathematically one can take a reactive system and turn it into an ordinary system by taking the paths as our new states. This is true but from the point of view of applications there is serious loss of information here as the applicability of the reactive system comes from the way the change occurs along the path. In any specific application, the states have meaning, the transitions have meaning and the paths have meaning. Therefore the changes in the system as we go along a path can have very important meaning in the context, which enhances the usability of the model.     

A group-level model of safety climate: Testing the effect of group climate on microaccidents in manufacturing jobs.

This article presents and tests a group-level model of safety climate to supplement the available organization-level model. Climate perceptions in this case are related to supervisory safety practices rather than to company policies and procedures. The study included 53 work groups in a single manufacturing company. Safety climate perceptions, measured with a newly developed scale, revealed both within-group homogeneity and between-groups variation. Predictive validity was measured with a new outcome measure, microaccidents, that refers to behavior-dependent on-the-job minor injuries requiring medical attention. Climate perceptions significantly predicted microaccident records during the 5-month recording period that followed climate measurement, when the effects of group- and individual-level risk factors were controlled. The study establishes an empirical link between safety climate perceptions and objective injury data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A mediation model linking dispatcher leadership and work ownership with safety climate as predictors of truck driver safety performance

The study was designed to test the effect of safety climate on safety behavior among lone employees whose work environment promotes individual rather than consensual or shared climate perceptions. The paper presents a mediation path model linking psychological (individual-level) safety climate antecedents and consequences as predictors of driving safety of long-haul truck drivers. Climate antecedents included dispatcher (distant) leadership and driver work ownership, two contextual attributes of lone work, whereas its proximal consequence included driving safety. Using a prospective design, safety outcomes, consisting of hard-braking frequency (i.e. traffic near-miss events) were collected six months after survey completion, using GPS-based truck deceleration data. Results supported the hypothesized model, indicating that distant leadership style and work ownership promote psychological safety climate perceptions, with subsequent prediction of hard-braking events mediated by driving safety. Theoretical and practical implications for studying safety climate among lone workers in general and professional drivers in particular are discussed.     

Supportive versus cognitive–behavioral intervention programs in achieving adjustment to home peritoneal kidney dialysis.

Two psychological interventions given for 8 weeks, supportive and cognitive–behavioral, were compared in achieving psychosocial adjustment to home peritoneal kidney dialysis. Participants were divided into 3 groups of patients and their spouses: a supportive group (18 couples), a cognitive–behavioral group (18 couples), and a no-intervention control group (24 couples). A group of 97 healthy participants served as a baseline control group. Self-report measurements were made before treatment (T?), halfway through (T?), and after treatment (T?). Results indicated that, without treatment, the no-intervention control group demonstrated a deterioration of psychosocial adjustment going from T? to T?. Both interventions were effective in aiding patients and spouses in maintaining psychosocial adjustment in comparison with the no-intervention control group, with few differences between treatments. Most improvement was obtained in the emotional, cognitive, and interpersonal areas, with smaller gains made in the behavioral area. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electronic Level Structure and Single Electron Tunneling Effects in CdSe Quantum Rods

Optical spectroscopy and scanning tunneling microscopy are used to study the size and shape dependence of the electronic states in CdSe quantum rods. Samples having average rod dimensions ranging from 10 to 60 nm in length and 3.5 to 7 nm in diameter, with aspect ratios varying between 3 to 12, were investigated. Both size-selective optical spectroscopy and tunneling spectra on single rods show that the level structure depends primarily on the rod diameter and not on length. With increasing diameter, the band gap and the excited state level spacings shift to the red. The level structure is assigned using a multi-band effective-mass model. We shall also discuss the effect of single electron charging on the tunneling spectra, possibly reflecting the quantum rod level degeneracy, and its dependence on the tunneling junction parameters.     

Theoretical Considerations Regarding the Optimization of Cardiac Assistance by lntraaortic Balloon Pumping

A lumped parameter model representing the effects of cardiac assistance by intraaortic balloon pumping was developed. The model permits closed-form calculations of important hemodynamic events in the system. The equations derived from the model were used to determine pumping parameters for optimum assistance. The model indicates that, in the ideal case, optimization of assistance requires instantaneous inflation of the balloon to maximum volume at end systole and instantaneous complete deflation at end diastole. Since an impulse flow rate is not realizable in practice, the model was used to investigate the effects of finite inflation/deflation periods. In general, it was found that fast inflation/deflation rates give higher benefits than slow rates. The optimal time to begin inflation is end systole. Timing of deflation was shown to involve a tradeoff between lower end diastolic pressure (achieved with early deflation) and increase of mean diastolic pressure and cardiac output (achieved with late deflation). The model's predictions were validated using a nonlinear distributed parameter digital computer model previously described. The lumped model results should make possible a quantitative as well as a simple approach to automatic control of in-series cardiac assistance.     

An improved mathematical solution for the calculation of the parabolic rate constant for the growth of nonuniformly doped oxides on dilute alloys

A method of calculation of the parabolic rate constant for the formation of scales of nonuniform composition over dilute alloys making use of the experimental profile of the impurity concentration through the scale but not requiring assumptions about the profile of the oxygen activity is proposed. Application of this procedure to a system for which a method developed previously and making use of an approximate form of the oxygen activity profile was unable to yield a stable value of the rate constant shows that this procedure is both more accurate and faster.