CORRELATION OF GLAZE-BODY STRESSES WITH THERMAL PROPERTIES OF WHITEWARE BODIES*

Several lead borosilicate glazes with high to low thermal expansion were applied to a bisque whiteware body having porosities ranging from 20 to 30%, and the thermal properties were studied. Test pieces were subjected to an autoclave test at 50, 150, and 300 lb. per sq. in. and to a thermal-shock test by quenching from 400° to 600°F. into cold water. The thermal-expansion curves for the various glazes and for the body at each porosity were determined on the interferometer. The glaze-fit ring test was used to determine the degree of tensile and compressive stress, and these stresses were plotted graphically with the body porosity. The resistance to crazing was increased in both the autoclave and thermal-shock tests as the thermal expansion of the glazes, as measured on the interferometer, decreased. The 10% porosity body gave the best results in the thermal-shock test. A close correlation was found between the thermal-expansion curves for the glazes and bodies of varying porosity and the stress characteristics shown by the glaze-fit ring test.     

Comparing Inspections and User Testing for the Evaluation of Virtual Environments

This article describes an experiment comparing three Usability Evaluation Methods: User Testing (UT), Document-based Inspection (DI), and Expert Inspection (EI) for evaluating Virtual Environments (VEs). Twenty-nine individuals (10 end-users and 19 junior usability experts) participated during 1 hr each in the evaluation of two VEs (a training VE and a 3D map). Quantitative results of the comparison show that the effectiveness of UT and DI is significantly better than the effectiveness of EI. For each method, results show their problem coverage: DI- and UT-based diagnoses lead to more problem diversity than EI. The overlap of identified problems amounts to 22% between UT and DI, 20% between DI and EI, and 12% between EI and UT for both virtual environments. The identification impact of the whole set of usability problems is 60% for DI, 57% for UT, and only 36% for EI for both virtual environments. Also reliability of UT and DI is significantly better than reliability of EI. In addition, a qualitative analysis identified 35 classes describing the profile of usability problems found with each method. It shows that UT seems particularly efficient for the diagnosis of problems that require a particular state of interaction to be detectable. On the other hand, DI supports the identification of problems directly observable, often related to learnability and basic usability. This study shows that DI could be viewed as a “4-wheel drive SUV evaluation type” (less powerful under certain conditions but able to go everywhere, with any driver), whereas UT could be viewed as a “Formula 1 car evaluation type” (more powerful but requiring adequate road and a very skilled driver). EI is found (considering all metrics) to be not efficient enough to evaluate usability of VEs.     

An automated microfluidic colourimetric sensor applied in situ to determine nitrite concentration

A stand-alone sensor system with integrated sub-systems is demonstrated. The system is portable and capable of in situ reagent-based nutrient analysis. The system is based on a low cost optical detection method, together with an automated microfluidic delivery system that is able to detect nitrite with a limit of detection (LOD) of 15 nM. The sensor was operated in situ at Southampton Dockhead for 57 h (December 2010) and 375 measurements were taken.     

Submillimeter features on injected acrylonitrile butadiene styrene parts: Visualization of the flow and numerical simulation

Numerical simulation of classical dimension parts with micrometric textures on their surface is still difficult to master. The limit condition of the calculations, and in particular, the implemented values, characteristics of the polymer and thermal exchanges (polymer/mold) strongly impact the results. Starting from a model with a 370 μm wide rib, by means of a numerical simulation, a study was done on the evolution of the material flow front velocities and the flow lengths in both the macroscopic part and the microgroove. This innovative visualization mold design was used to determine the velocities from an experimental perspective and to discuss the calculation conditions. On the one hand, there are significant differences regarding the choice of the no flow temperature (~ 40 K) used in the calculation code, the analytical heat transfer equation as well as the experimental results. On the other hand, according to the no flow temperature, it may be necessary to consider, during the filling phase, a perfect mold/polymer thermal contact in the groove. Depending in particular on the injection velocity and the geometry of the micro textures, a characteristic time can be determined which defines an optimal operating point for the topographic texture of the part.     

Stealthy output injection attacks on control systems with bounded variables

As more and more critical infrastructures such as transportation, power systems and water are being embedded with sensing and control and linked to the Internet, the resulting security vulnerability can be exploited to inflict systematic damage to the connected physical systems. The class of false-data injection attacks is of particular interest as it only requires the ability to compromise the measurements. We construct such attacks, that are stealthy to set-membership-based anomaly detectors over widely used constrained control systems with bounded disturbances. The design of robust controllers and detectors based on the ability to withstand disturbance lets the attacker masquerade itself as disturbance and necessitates the development of a disturbance set-estimator as a soft-constrained optimisation problem. We then formulate another constrained optimisation problem that maximises the state estimation error by manipulating measurements and results in a computable performance loss and derive its explicit solution as the attack vector. These methods are used to demonstrate the vulnerability of a test system, with attacker having limited knowledge of the control system.     

Laboratory and In Situ Tests for Long-Term Hydraulic Conductivity of a Cement-Bentonite Cutoff Wall

Slurry trench cutoff walls, constructed using self-hardening slag-cement-bentonite (Slag-CB), are the most common form of in-ground vertical contaminant barrier in the U.K., Europe, and Japan, and are increasingly being used in the United States. This paper presents a case study of the hydraulic conductivity evaluation of an 11-year-old Slag-CB wall material at a sulfate-contaminated site, using different in situ techniques and laboratory tests. The laboratory results suggest that the hydraulic conductivity of the samples, which vary in age from 4 weeks to 11 years, decreases with time for the first 3 years but then remains constant. The results indicate that the long-term performance of these containment walls is influenced by various parameters such as aging, the type/duration of contaminant exposure, mixing of surrounding soil during construction, and wall depth. Piezocone tests, packer tests, and self-boring permeameter tests were carried out in the field to determine the suitability of different in situ techniques and compare with the laboratory results. The hydraulic conductivity is affected by the type of in situ technique used and the geometric scale of the test section.     

Flow regime determination in horizontal hydrotransport using non‐intrusive acoustic probes

A variety of flow regimes may be observed in the hydrotransport of solids. Maintaining a consistent operation requires rapid detection of any change in flow regime. The objective of this study was to develop reliable, non‐intrusive, and on‐line methods for flow regime detection in a hydrotransport pipe based on acoustic measurements. Slurries were transported in a 0.05 m diameter stainless steel hydrotransport pipe. Acoustic measurements were recorded by microphones along the length of the horizontal pipe. Two flow regimes were observed: suspended solids flow and flow over settled solids. Cycle and frequency analyses of the acoustic signals provided reliable identification of these flow regimes.     

Activities,postures and comfort perception of train passengers as input for train seat design

Working in the train is a part of new ways of working. However, the ideal working position is unknown. Moreover, the ideal position for leisure and relaxing is also unknown. This article defines what activities train passengers mainly perform and which corresponding postures are seen. Based on the observations on actual train rides, four main activities could be identified: Reading, Staring/sleeping, Talking and Working on laptop. Working on laptop was the activity with the longest duration and talking had the shortest duration. Associated with these four activities, a top eight of different postures were observed. Except for headrest comfort, comfort scores were not significantly different between activities. The top eight corresponding postures combined with comfort scores showed that per activity different postures were observed and the comfort scores varied in relation to the combination of posture and activity. Nearly for all activities, the majority of passengers preferred adjustability options to fit the seat to the performed activity.     

A novel fluidized and induction heated microreactor for catalyst testing

The jiggled bed reactor (JBR) is a state‐of‐the‐art batch fluidized microreactor designed and developed to test catalysts for endothermic reactions. The solid particles in the microreactor are mechanically fluidized by agitating the reactor using a linear pneumatic actuator. An external induction field heats up vertical metal wires installed inside the reactor bed to generate heat rapidly and uniformly within the bed of solid particles, while eliminating hot spots and large temperature gradients. Image and signal processing techniques were utilized to investigate how the fluidization dynamics of the solid particles are affected by the amplitude and frequency of the vibrations, and the size distribution and the mass of the particles. The results show that the microreactor is very flexible: operating conditions can be optimized to successfully fluidize any type of catalyst. Heat‐transfer coefficients between heating surfaces and the bed are similar to the coefficients that could be obtained in a well‐bubbling fluidized bed. This confirms the excellent quality of the fluidization achieved with the new JBR. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3107–3122, 2014