Synthesis and characterization of microporous and mesoporous catalysts for shale gas upgrading

The petroleum industry is gradually shifting from using naphtha to ethane as its feedstock and new ethane steam crackers are being built. Using ethane as a feedstock produces more ethene and less co-products such as propene, aromatics and C4 alkenes. Thus, the shift in feedstock will reduce the availability of these co-products. Developing methods for the interconversion of alkenes, and specifically using ethene as a reactant, can solve this problem. This project focuses on synthesis and characterization of zeolites with the BEA framework topology, and their nickel exchanged versions as potential ethene dimerization catalysts. In future work, these materials will be used to carry out catalytic studies for ethene dimerization. Nickel exchanges were carried out using nickel nitrate Ni(NO3)2 solution on commercial aluminosilicate samples from Clariant (HCZB-25 Si/Al=12.5) and Zeolyst (CBV Si/Al=12.5) and an in-house synthesized aluminosilicate (Si/Al=13). Nickel exchange was determined to reach equilibrium by 16 hours at 75oC. Nickel exchanges were performed at this equilibration time with varying nickel nitrate molarities (0.005-0.1M), but keeping all other factors constant (temperature at 75oC, stirring at 300 R.P.M), to obtain ion-exchange isotherms that can be used to estimate the fraction of framework metal exchange sites. Zincosilicate molecular sieve CIT-6 samples were also synthesized with different Si/Zn molar ratios (20, 33, 40, 70, 100), in which changes in the Si/Zn ratio in the reactant gel led to changes in the time for crystallization

Policy, Regulations and Standards in Prognostics and Health Management

As the field of PHM matures, it needs to be aware of the regulations, policies, and standards that will both impose boundaries as well as provide guidance for operations. All three - regulations, policies, and standards - provide information on how to design or operate something, but with different degrees of enforceability. Policies include both public policies as well as organizational policies. Operators may be required to adhere to public policies(say, an environmental policy which provides guidance for the pollution prevention act (the latter is a US law)) whereas organisational often reflect policies that come out of strategic considerations within private organizations (such as maintenance policies). Regulations (such as aeronautics or nuclear energy) typically impose binding rules of engagement and are imposed by regulatory bodies that are responsible for a particular field. Standards, in contrast, are community-consensus guidelines that are meant to provide benefit to the community by describing best practices. Adoption of such guidelines is entirely voluntary but may provide benefits by not having to reinvent the wheel and for finding common ground amongst other adopters. Awareness of both guidelines and barriers will enable practitioners in adopting best practices within the legal constraints. This paper provides an overview of the current regulations, policies, and standards in the field of Prognostics and Health Management

Developing IVHM Requirements for Aerospace Systems

The term Integrated Vehicle Health Management (IVHM) describes a set of capabilities that enable sustainable and safe operation of components and subsystems within aerospace platforms. However, very little guidance exists for the systems engineering aspects of design with IVHM in mind. It is probably because of this that designers have to use knowledge picked up exclusively by experience rather than by established process. This motivated a group of leading IVHM practitioners within the aerospace industry under the aegis of SAE's HM-1 technical committee to author a document that hopes to give working engineers and program managers clear guidance on all the elements of IVHM that they need to consider before designing a system. This proposed recommended practice (ARP6883 [1]) will describe all the steps of requirements generation and management as it applies to IVHM systems, and demonstrate these with a "real-world" example related to designing a landing gear system. The team hopes that this paper and presentation will help start a dialog with the larger aerospace community and that the feedback can be used to improve the ARP and subsequently the practice of IVHM from a systems engineering point-of-view

Thermodynamic Basis for the Emergence of Genomes during Prebiotic Evolution

The RNA world hypothesis views modern organisms as descendants of RNA molecules. The earliest RNA molecules must have been random sequences, from which the first genomes that coded for polymerase ribozymes emerged. The quasispecies theory by Eigen predicts the existence of an error threshold limiting genomic stability during such transitions, but does not address the spontaneity of changes. Following a recent theoretical approach, we applied the quasispecies theory combined with kinetic/thermodynamic descriptions of RNA replication to analyze the collective behavior of RNA replicators based on known experimental kinetics data. We find that, with increasing fidelity (relative rate of base-extension for Watson-Crick versus mismatched base pairs), replications without enzymes, with ribozymes, and with protein-based polymerases are above, near, and below a critical point, respectively. The prebiotic evolution therefore must have crossed this critical region. Over large regions of the phase diagram, fitness increases with increasing fidelity, biasing random drifts in sequence space toward ‘crystallization.’ This region encloses the experimental nonenzymatic fidelity value, favoring evolutions toward polymerase sequences with ever higher fidelity, despite error rates above the error catastrophe threshold. Our work shows that experimentally characterized kinetics and thermodynamics of RNA replication allow us to determine the physicochemical conditions required for the spontaneous crystallization of biological information. Our findings also suggest that among many potential oligomers capable of templated replication, RNAs may have evolved to form prebiotic genomes due to the value of their nonenzymatic fidelity

Effect of Fibrin Glue on the Biomechanical Properties of Human Descemet's Membrane

10.1371/journal.pone.0037456PLoS ONE75

A Model-Based Engineering Approach for Evaluating Software-Defined Radio Architecture

In product development, important specification and design decisions must be made at various stages of the lifecycle that include design, manufacturing, operations, and support. However, making these decisions becomes more complex when a multi-disciplinary team of stakeholders is involved in system-level or subsystem-level architecture and design decisions. Model-Based Engineering (MBE) approaches are enabling a digital thread of connected data and models. This work demonstrates a novel MBE approach that incorporates a model-based systems engineering (MBSE) method and a multi-criteria decision-making (MCDM) method to determine the best architecture solution that aligns with stakeholder needs and objectives over multiple domains. This approach demonstrates the connection of a system descriptive model, modeled using the systems modeling language (SysML), to underlying physics-based engineering models for the purpose of better predicting the technical performance of systems during the architecture development phase. This approach is demonstrated for a common aerospace communications application, a software-defined radio. This novel MBE approach supports digital transformation at organizations and allows for earlier design validation, enabling designers to test and select the best system architecture from many candidates and validate that the design meets stakeholder needs

A Lagrangian relaxation based approach to schedule asset overhaul and repair services

Abstract—Overhaul and repair services are important segments of the remanufacturing industry, and are characterized by complicated disassembly, repair and assembly process plans, stochastic operations, and the usage of rotable inventory. In view of today’s time-based competition, effectively scheduling such services and managing rotable inventory and uncertainties are becoming imperative to achieve on-time deliveries and low overall costs. In this paper, a novel formulation for overhaul and repair services is presented where key characteristics, such as uncertain asset arrivals and operation processing times, and rotable parts are abstracted to model an overhaul center and multiple repair shops in a distributed framework to reflect organizational structures. Interactions between the overhaul center and repair shops are described by sets of coupling constraints across the organizations. Rotable inventory dynamics is formulated in terms of repair operation completio