Solidification of undercooled liquids

During rapid solidification processing (RSP) the amount of liquid undercooling is an important factor in determining microstructural development by controlling phase selection during nucleation and morphological evolution during crystal growth. While undercooling is an inherent feature of many techniques of RSP, the deepest undercoolings and most controlled studies have been possible in carefully prepared fine droplet samples. From past work and recent advances in studies of nucleation kinetics it has become clear that the initiation of crystallization during RSP is governed usually by heterogeneous sites located at surfaces. With known nucleant sites, it has been possible to identify specific pathways of metastable phase formation and microstructural development in alloys. These advances have allowed for a clearer assessment of the interplay between undercooling, cooling rate and particle size statistics in structure formation. New approaches to the examination of growth processes have been developed to follow the thermal behavior and morphology in small samples in the period of rapid crystallization and recalescence. Based upon the new experimental information from these studies, useful models can be developed for the overall solidification process to include nucleation behavior, thermodynamic constraints, thermal history, growth kinetics, solute redistribution and resulting structures. From the refinement of knowledge concerning the underlying factors that govern RSP a basis is emerging for an effective alloy design and processing strategy

An improved method for quantitative risk assessment of unconfined offshore installations subjected to gas explosions

Previous related research has focused on consequences analysis of confined rather than unconfined structures against explosion accidents. This paper introduces an improved method for quantitative risk assessment of unconfined offshore installations subjected to gas explosions. In the present study, a floating, production, storage, and offloading unit (FPSO) is given as an example to present the proposed method. Instead of the most unfavorable scenario, lots of random scenarios are selected by the probabilistic sampling approach. The method for determining the equivalent gas cloud position is illustrated in the conversion between dispersion and explosion scenarios. Maximum and average overpressures are obtained by computational fluid dynamics (CFD) simulation. Besides overpressure exceedance curves, the combination of overpressure and probability method is adopted based on the definition of risk. This work allows finer scenarios’ sampling results and reduces the computational costs

T1T_1- and T2T_2-spin relaxation time limitations of phosphorous donor electrons near crystalline silicon to silicon dioxide interface defects

A study of donor electron spins and spin--dependent electronic transitions involving phosphorous ($^{31}$P) atoms in proximity of the (111) oriented crystalline silicon (c-Si) to silicon dioxide (SiO$_{2}$) interface is presented for [$^{31}$P] = 10$^{15}$ $\mathrm{cm}^{-3}$ and [$^{31}$P] = 10$^{16}$ $\mathrm{cm}^{-3}$ at about liquid $^4$He temperatures ($T = 5$ $\mathrm{K} - 15$ $\mathrm{K}$). Using pulsed electrically detected magnetic resonance (pEDMR), spin--dependent transitions between the \Phos donor state and two distinguishable interface states are observed, namely (i) \Pb centers which can be identified by their characteristic anisotropy and (ii) a more isotropic center which is attributed to E$^\prime$ defects of the \sio bulk close to the interface. Correlation measurements of the dynamics of spin--dependent recombination confirm that previously proposed transitions between \Phos and the interface defects take place. The influence of these electronic near--interface transitions on the \Phos donor spin coherence time $T_2$ as well as the donor spin--lattice relaxation time $T_1$ is then investigated by comparison of spin Hahn--echo decay measurements obtained from conventional bulk sensitive pulsed electron paramagnetic resonance and surface sensitive pEDMR, as well as surface sensitive electrically detected inversion recovery experiments. The measurements reveal that both $T_2$ and $T_1$ of \Phos donor electrons spins in proximity of energetically lower interface states at $T\leq 13$ K are reduced by several orders of magnitude

Inviting the Perspectives of Refugee Mental Health Interpreters: A Critical Narrative Analysis

The research literature lacks examination into several areas concerning mental health interpretation for refugee clients. This includes the management of interpreters’ vicarious trauma and retraumatization, interpreter’s perspectives on the appropriateness of hiring refugees as mental health interpreters, how interpreters define their trauma as well as their clients’ trauma, and support that interpreters seek for their traumatic responses from their work. The literature is also missing an analysis of how oppressive power differentials are repeated in workplace institutions, specifically for refugee mental health interpreters. Thus, this study aimed to invite the perspectives of refugee mental health interpreters on several issues pertaining to their work with refugee clients. The method of choice for this study is Critical Narrative Analysis (CNA). Critical Narrative Analysis is a method of analysis that fits within the broader category of hermeneutic phenomenology and combines hermeneutic phenomenology with critical theory (Davidsen, 2013; Langdridge, 2007; Peter & Polgar, 2020). The study utilized criterion-based sampling and there were four participants total. From the findings, participants were able to respond to the research questions of how they define trauma, what the benefits and harms are of hiring refugees as mental health interpreters are, what power dynamics exist in their workplaces, how they manage their traumatic responses, and what supports they sought for their interpretation work. The results from this study ultimately added to themes that exist in the little literature on this topic and added novel information. For example, one participant used the concept of generational trauma to define their own experience of trauma. Another participant hypothesized about why they had experienced similar experiences as their clients, yet they had responded differently. Additionally, another participant stated how they experienced their trauma collectively, which suggests collective healing methods to respond to collective trauma. This study also aimed to present concrete suggestions of how to aid interpreters and was able to discern several, including specific trainings (e.g. mental health, population-specific, work-life boundaries), breaks between session, and factors in supervision such as positive feedback from supervisors

Business process improvement with the AB-BPM methodology

A fundamental assumption of Business Process Management (BPM) is that redesign delivers refined and improved versions of business processes. This assumption, however, does not necessarily hold, and any required compensatory action may be delayed until a new round in the BPM life-cycle completes. Current approaches to process redesign face this problem in one way or another, which makes rapid process improvement a central research problem of BPM today. In this paper, we address this problem by integrating concepts from process execution with ideas from DevOps. More specifically, we develop a methodology called AB-BPM that offers process improvement validation in two phases: simulation and AB tests. Our simulation technique extracts decision probabilities and metrics from the event log of an existing process version and generates traces for the new process version based on this knowledge. The results of simulation guide us towards AB testing where two versions (A and B) are operational in parallel and any new process instance is routed to one of them. The routing decision is made at runtime on the basis of the achieved results for the registered performance metrics of each version. Our routing algorithm provides for ultimate convergence towards the best performing version, no matter if it is the old or the new version. We demonstrate the efficacy of our methodology and techniques by conducting an extensive evaluation based on both synthetic and real-life data

Optimal Design of Submarine Pressure Hull Structures using Genetic Algorithm

In this paper, a method is presented for the optimal design of submarine pressure hull structures by taking advantage of genetic algorithm techniques. The objective functions and design constraints in the process of structural optimization are based on the ultimate limit states of hull structures. One of the benefits associated with the utilization of genetic algorithm is that the optimization process can be completed within short generations of design variables for the pressure hull structure model. Applied examples confirm that the proposed method is useful for the optimal design of submarine pressure hull structures. Details of the design procedure with applied examples are documented. The conclusions and insights obtained from the study are summarized

Verification of the Parallel Pin-Wise Core Simulator pCTF/PARCSv3.2 in Operational Control Rod Drop Transient Scenarios

This is an Accepted Manuscript of an article published by Taylor & Francis in Nuclear Science and Engineering on 2017, available online: https://www.tandfonline.com/doi/full/10.1080/00295639.2017.1320892[EN] Thanks to advances in computer technology, it is feasible to obtain detailed reactor core descriptions for safety analysis of the light water reactor (LWR), in order to represent realistically the fuel elements design, as is the case for three-dimensional coupled simulations for local neutron kinetics and thermal hydraulics. This scenario requires an efficient thermal-hydraulic code that can produce a response in a reasonable time for large-scale, detailed models. In two-fluid codes, such as the thermal-hydraulic subchannel code COBRA-TF, the time restriction is even more important, since the set of equations to be solved is more complex. We have developed a message passing interface parallel version of COBRA-TF, called pCTF. The parallel code is based on a cell-oriented domain decomposition approach, and performs well in models that consist of many cells. The Jacobian matrix is computed in parallel, with each processor in charge of calculating the coefficients related to a subset of the cells. Furthermore, the resulting system of linear equations is also solved in parallel, by exploiting solvers and preconditioners from PETSc. The goal of this study is to demonstrate the capability of the recently developed pCTF/PARCS coupled code to simulate large cores with a pin-by-pin level of detail in an acceptable computational time, using for this purpose two control rod drop operational transients that took place in the core of a three-loop pressurized water reactor. As a result, the main safety parameters of the core hot channel have been calculated by the coupled code in a pin level of detail, obtaining best estimate results for this transient.This work has been partially supported by the Universitat Politecnica de Valencia under Projects COBRA_PAR (PAID-05-11-2810) and OpenNUC (PAID-05-12), and by the Spanish Ministerio de Economia y Competitividad under Projects SLEPc-HS (TIN2016-75985-P) and NUC-MULTPHYS (ENE2012-34585).Ramos Peinado, E.; Roman Moltó, JE.; Abarca Giménez, A.; Miró Herrero, R.; Bermejo, JA.; Ortego, A.; Posada-Barral, JM. (2017). Verification of the Parallel Pin-Wise Core Simulator pCTF/PARCSv3.2 in Operational Control Rod Drop Transient Scenarios. Nuclear Science and Engineering. 187(3):254-267. https://doi.org/10.1080/00295639.2017.1320892S2542671873Cuervo, D., Avramova, M., Ivanov, K., & Miró, R. (2006). Evaluation and enhancement of COBRA-TF efficiency for LWR calculations. Annals of Nuclear Energy, 33(9), 837-847. doi:10.1016/j.anucene.2006.03.011Ramos, E., Roman, J. E., Abarca, A., Miró, R., & Bermejo, J. A. (2016). Control rod drop transient analysis with the coupled parallel code pCTF-PARCSv2.7. Annals of Nuclear Energy, 87, 308-317. doi:10.1016/j.anucene.2015.09.016T. DOWNAR et al. “PARCS v2.7 U.S. NRC Core Neutronics Simulator: User Manual” (2006).T. DOWNAR et al. “PARCS v2.7 U.S. NRC Core Neutronics Simulator: Theory Manual” (2006)

Droplet microactuator system

The present invention relates to a droplet microactuator system. According to one embodiment, the droplet microactuator system includes: (a) a droplet microactuator configured to conduct droplet operations; (b) a magnetic field source arranged to immobilize magnetically responsive beads in a droplet during droplet operations; (c) a sensor configured in a sensing relationship with the droplet microactuator, such that the sensor is capable of sensing a signal from and/or a property of one or more droplets on the droplet microactuator; and (d) one or more processors electronically coupled to the droplet microactuator and programmed to control electrowetting-mediated droplet operations on the droplet actuator and process electronic signals from the sensor