Creep of Mn1-δO

Constant-load creep tests have been performence nonstoichiometnc (100) oriented MnO single crystals between 900° and 1400°C. Tests were conducted under a controlled oxygen partial pressure to ensure that dislocation-climb recovery was controlled by diffusion of either oxygen vacancies (low pO₂) or oxygen interstitials (high po₂). Within experimental error, the activation energies and the stress exponents are independent of oxygen partial pressure. The activation energy measured for T≤1000°C is about half of that measured for higher temperatures.     

Plastic Deformation Mechanisms in SiC-Whisker-Reinforced Alumina

SiC-whisker-reinforced Al₂O₃ samples (SiC_w/Al₂O₃), obtained from three different manufacturers, containing 0–30 vol% SiC have been crept under compression at 1400°C in flowing argon. Compressive creep tests and microstructural observations have been used to characterize the plastic deformation mechanisms. The presence of whiskers decreased the creep rate by reducing grain-boundary sliding. Damage formation was increased, however, because the whiskers acted as stress concentration sites. For specimens with whisker loadings greater than 15%, the absolute creep rate was not strongly dependent on whisker concentration, and the formation of cavitation damage was negligible below a critical stress that depended on the fabrication procedure of the specimen. This creep regime was characterized by a stress exponent of approximately 1, in which deformation occurred primarily by diffusional flow. For the materials with less SiC, the deformation occurred primarily by grain-boundary sliding.     

Dynamics And Assessment of Some Control Strategies of a Simulated Industrial Rotary Dryer

Rotary dryers are widely used for the continuous drying of minerals and chemicals on a large scale. Hot gases are passed parallel to the flowing solid to achieve the desired product moisture content. Because these dryers are energy intensive, it is mandatory to operate them as efficiently as possible to respond to economic pressures. Using a dynamic rotary dryer simulator for mineral concentrate, five control strategies are evaluated and compared. Two control strategies are based on PI controllers and the others use neural network models. Results clearly show that a feedforward action, in conjunction with a PI controller or incorporated within the structure of a neural network model, led to the best performances provided an accurate measurement of the feed moisture content is available.     

Novel methodology for assessing a ranked Pareto domain: Drift group analysis

Recent advances in the field of operations research and systems science have yielded rigorous multi-criteria optimisation techniques that can be successfully applied to processes having numerous conflicting criteria. One such method, referred to as the Rough Set Method, incorporates the knowledge of an expert within the optimisation algorithm. The result of this process is a set of all possible candidates for the optimal solution, called the Pareto domain, that has been ranked according to the expert's preferences.In addition to providing the optimal solution to the problem at hand, the ranked Pareto domain can yield useful information regarding the robustness of the optimal operating point. This paper presents a novel approach for evaluating the ranked domain, referred here as the drift group analysis, which is applied to the optimisation of a thermomechanical pulping process. This analysis may also prove useful in the design of control systems for such processes.     

Simultaneous Measurement Bias Correction and Dynamic Data Reconciliation

The presence of measurement bias and random noise significantly deteriorates the information quality of plant data. Data reconciliation techniques for steady-state processes have been widely applied to processing industries to improve the accuracy and precision of the raw measurements. This paper develops an algorithm for simultaneous bias correction and data reconciliation for dynamic processes. The algorithm considers process model error as an important contributing factor in the estimation of the measurement bias and process state variables. It employs black-box models for the process as would be done when phenomenological models are difficult or impractical to obtain. Simulation results of a distillation column demonstrated that this algorithm effectively compensates constant and non-constant measurement biases yielding much improved reconciled values of process variables. It has computational advantages over previously proposed algorithms based on non-linear dynamic data reconciliation because an analytical solution is available when using linear process models to approximate the process.     

Suspended core tellurite glass optical fibers for infrared supercontinuum generation

We report the fabrication and characterization of tellurite TeO₂-ZnO-Na₂O (TZN) microstructured suspended core optical fibers (MOFs). These fibers are designed for infrared supercontinuum generation with zero dispersion wavelength (ZDW) at 1.45 μm. The measured losses at this wavelength are approximately 6 dB/m for a MOF with a 2.2 μm diameter core. The effective area of a particular fiber is 3.5 μm² and the nonlinear coefficient is calculated to be 437 W⁻¹km⁻¹. By pumping a 20 cm long fiber at 1.56 μm with a sub-nJ femtosecond laser source, we generate a supercontinuum (SC) spanning over 800 nm in the 1-2 μm wavelength range.     

Heat transfer to a silicon carbide/water nanofluid

Heat transfer experiments were performed with a water-based nanofluid containing 170-nm silicon carbide particles at a 3.7% volume concentration and having potential commercial viability. Heat transfer coefficients for the nanofluid are presented for Reynolds numbers ranging from 3300 to 13,000 and are compared to the base fluid water on the bases of constant Reynolds number, constant velocity, and constant pumping power. Results were also compared to predictions from standard liquid correlations and a recently altered nanofluid correlation. The slip mechanisms of Brownian diffusion and thermophoresis postulated in the altered correlation were investigated in a series of heating and cooling experiments.     

Compact electrochemical bifunctional NOx/O2 sensor with metal/metal oxide internal reference electrode for high temperature applications

Simultaneous measurement of total NO_x and O₂ using two electrochemical methods are demonstrated using metal/metal oxide internal oxygen reference electrode-based sensors at high temperatures. The Pd/PdO-containing reference chamber was sealed within a stabilized zirconia superstructure by a high pressure/temperature plastic deformation bonding method exploiting grain boundary sliding between the ceramic components. Amperometric and potentiometric NO_x sensing devices were assembled on the outside of the sensor. Pt-loaded zeolite Y was used to obtain total NO_x capability. Both the amperometric and potentiometric type sensors showed total NO_x response, with the potentiometric device showing better NO_x/O₂ signal stability and lower NO_x–O₂ cross-interference. Since these sensors do not require plumbing for reference air, there is more flexibility in the placement of such sensors in a combustion stream.     

Effects of target location, stature and hand grip type on in-vehicle reach discomfort

In order to improve car interior design, data of perceived discomfort and reach posture were collected for 75 different target locations. Altogether, 24 males and females of different statures participated in the experiment. In addition to three-finger grip, index fingertip reach and five finger grip were also compared. The effects of target location, stature and hand grip on reach discomfort were analysed. Predictive regression equations were provided. In addition to the confirmation of target location effects, the results showed that seat back and steering wheel affected discomfort. Their effects differed according to the subject's anthropometry. A detailed analysis of possible interference between the car interior and reach movement showed that short females were more likely impeded by the seat back when a target was close to the body. A significant difference between three hand grip types could be explained by the change of hand reach distance when changing hand grip type. STATEMENT OF RELEVANCE: The present study analysed the effects of target location, stature and hand grip type on reach discomfort, based on the statistical analysis of subjective ratings when reaching a target in a vehicle. The results would help to optimise the location of automotive controls for improving car interior design.