NONEQUILIBRIUM MODELING OF REACTIVE ABSORPTION PROCESSES

A nonequilibrium stage model of reactive absorption processes has been developed, considering the interactions between reaction and diffusion in the film region. Dynamic and steady-state film models have been incorporated into the process model for low and highly soluble gases respectively. The model was validated against experimental data. The data were obtained from a pilot-plant absorption column in which simultaneous reactive absorption of ammonia and carbon dioxide in aqueous partially carbonated ammonia solution occurred. A comparison between simulation results and the experimental data showed that the model could reasonably predict the process. The model predictions were also compared with those of a process model including enhancement factor. The results indicate that using a film model leads to a more accurate process model than applying enhancement factor.     

Input variable selection in time-critical knowledge integration applications: A review,analysis, and recommendation paper

The purpose of this research is twofold: first, to undertake a thorough appraisal of existing Input Variable Selection (IVS) methods within the context of time-critical and computation resource-limited dimensionality reduction problems; second, to demonstrate improvements to, and the application of, a recently proposed time-critical sensitivity analysis method called EventTracker to an environment science industrial use-case, i.e., sub-surface drilling.Producing time-critical accurate knowledge about the state of a system (effect) under computational and data acquisition (cause) constraints is a major challenge, especially if the knowledge required is critical to the system operation where the safety of operators or integrity of costly equipment is at stake. Understanding and interpreting, a chain of interrelated events, predicted or unpredicted, that may or may not result in a specific state of the system, is the core challenge of this research. The main objective is then to identify which set of input data signals has a significant impact on the set of system state information (i.e. output). Through a cause-effect analysis technique, the proposed technique supports the filtering of unsolicited data that can otherwise clog up the communication and computational capabilities of a standard supervisory control and data acquisition system.The paper analyzes the performance of input variable selection techniques from a series of perspectives. It then expands the categorization and assessment of sensitivity analysis methods in a structured framework that takes into account the relationship between inputs and outputs, the nature of their time series, and the computational effort required. The outcome of this analysis is that established methods have a limited suitability for use by time-critical variable selection applications. By way of a geological drilling monitoring scenario, the suitability of the proposed EventTracker Sensitivity Analysis method for use in high volume and time critical input variable selection problems is demonstrated.     

White Si–O–C Ceramic: Structure and Thermodynamic Stability

While pyrolysis of a polysiloxane precursor in argon typically produces a black amorphous Si–O–C ceramic containing “free” carbon (sp² carbon), pyrolyzing the same precursor in hydrogen leads to a white amorphous ceramic with a negligible amount of sp² carbon and a considerable hydrogen content. ²⁹Si magic‐angle‐spinning nuclear magnetic resonance (MAS NMR) spectroscopy confirms the existence of very similar bonding environments of Si atoms in the Si–O–C network for both samples. In addition, ¹H NMR spectroscopic measurements on both samples reveal that the hydrogen atoms are bonded mainly to carbon. For the thermodynamic analysis, the enthalpies of formation with respect to the most stable components (SiO₂, SiC, C) of the black‐and‐white Si–O–C samples obtained after the pyrolysis at 1100°C are determined using high‐temperature oxidative drop‐solution calorimetry in a molten oxide solvent. The white ceramic is 6 kJ/g‐atom more stable in enthalpy than the black one. Although the role of hydrogen in the thermodynamic stability of the white sample remains ambiguous, the thermodynamic findings and structural analysis suggest that the existence of sp²‐bonded carbon in the amorphous network of polymer derived Si–O–C ceramics does not provide additional thermodynamic stability to the ceramic.     

Equilibrium,kinetics and breakthrough studies for adsorption of hydrogen fluoride on sodium fluoride

In this study, adsorption of hydrogen fluoride on sodium fluoride adsorbent is investigated through an experimental and theoretical study. This process is very important in a section of a total process of producing and making pure fluorine gas in uranium conversion industry. For applying the section of experimental study, experimental sample of differential adsorbed bed was designed and manufactured with necessary side equipment and the required experiments were applied in 22 and 54 °C. By the use of experimental results, Isotherm curve of hydrogen fluoride adsorption on sodium fluoride adsorbent was obtained which is the main tool for designing of adsorption bed. By considering the experimental results and adsorption models applied in this study, it can be concluded that equilibrium data were well represented by a langmuir isotherm equation with maximum adsorption capacities of 1.908 and 0.750 g HF/g NaF in 22 and 54 °C.     

Coupled surface-enhanced Raman spectroscopy and electrical conductivity measurements of 1,4-phenylene diisocyanide in molecular electronic junctions

Probing the structure of molecules in a metal-molecule-metal junction under an applied voltage is critical for understanding molecular electron transport properties. We present an approach that allows recording surface-enhanced Raman spectra simultaneously with electrical measurements of a monolayer of molecules in molecular electronic junctions. 1,4-Phenylene diisocyanide in two different types of junctions was used to illustrate the approach. The results show that the molecular integrity was intact in the molecular junctions and under the applied bias. The monolayer sensitivity of the approach provides a new powerful tool for characterizing molecular structure in a molecular electronic junction.     

Feeder growth: a new method for automatic optimal feeder design in gravity casting processes

The optimal feeder design in gravity casting processes is considered. The design problem is formulated as an additive, growth-like, evolutionary topology optimization problem. The initial design of the presented method is a casting part which is placed in a suitable environmental mould box. The method is composed of three stages: determining the feeder-neck connection point on the casting surface, constructing the feeder-neck and the feeder growth. During the growth stage, the feeder topology is changed gradually until satisfying some predefined criteria. The design of multiple feeders is also considered in this work. In the presented method, feeders are designed in a descending order of their sizes. The success of the proposed method is supported by an illustrative example.     

Lithiophilic Nanowire Guided Li Deposition in Li Metal Batteries

Lithium (Li) metal batteries (LMBs) provide superior energy densities far beyond current Li-ion batteries (LIBs) but practical applications are hindered by uncontrolled dendrite formation and the build-up of dead Li in “hostless” Li metal anodes. To circumvent these issues, we created a 3D framework of a carbon paper (CP) substrate decorated with lithiophilic nanowires (silicon (Si), germanium (Ge), and SiGe alloy NWs) that provides a robust host for efficient stripping/plating of Li metal. The lithiophilic Li₂₂Si₅, Li₂₂(Si_0.5Ge_0.5)_5, and Li₂₂Ge₅ formed during rapid Li melt infiltration prevented the formation of dead Li and dendrites. Li₂₂Ge₅/Li covered CP hosts delivered the best performance, with the lowest overpotentials of 40 mV (three times lower than pristine Li) when cycled at 1 mA cm⁻²/1 mAh cm⁻² for 1000 h and at 3 mA cm⁻²/3 mAh cm⁻² for 500 h. Ex situ analysis confirmed the ability of the lithiophilic Li₂₂Ge₅ decorated samples to facilitate uniform Li deposition. When paired with sulfur, LiFePO_4, and NMC811 cathodes, the CP-LiGe/Li anodes delivered 200 cycles with 82%, 93%, and 90% capacity retention, respectively. The discovery of the highly stable, lithiophilic NW decorated CP hosts is a promising route toward stable cycling LMBs and provides a new design motif for hosted Li metal anodes.     

Automated Quality Characterization for Composites Using Hybrid Ultrasonic Imaging Techniques

An enhanced technique using image processing has been developed for automated ultrasonic inspection of composite materials, such as glass/carbon-fibre-reinforced polymer (GFRP or CFRP), to ascertain their structural healthiness. The proposed technique is capable of identifying the abnormality features buried in the composite by image filtering and segmentation applied to ultrasonic C-Scan images. This work presents results performed on two composite samples with simulated delamination defects. A local gating scheme is applied to raw A-Scan data for improved contrast between defective and healthy regions in the produced C-Scan image. In this test campaign, different filtering and thresholding algorithms are evaluated and compared in terms of their effectiveness on defect identification. The accuracies of less than 3 mm and 1.11 mm were attained for the defect size and depth, respectively. The results demonstrates the applicability of the proposed technique for accurate defect localization and characterization of composite materials.     

A haptic interface for computer-integrated endoscopic surgery and training

Haptic feedback has the potential to provide superior performance in computer-integrated surgery and training. This paper discusses the design of a user interface that is capable of providing force feedback in all the degrees of freedom (DOFs) available during endoscopic surgery. Using the Jacobian matrix of the haptic interface and its singular values, methods are proposed for analysis and optimization of the interface performance with regard to the accuracy of force feedback, the range of applicable forces, and the accuracy of control. The haptic user interface is used with a sensorized slave robot to form a master–slave test-bed for studying haptic interaction in a minimally invasive environment. Using the master–slave test-bed, teleoperation experiments involving a single degree of freedom surgical task (palpation) are conducted. Different bilateral control methods are compared based on the transparency of the master–slave system in terms of transmitting the critical task-related information to the user in the context of soft-tissue surgical applications.