Fragment formation in the break up of a drop falling in a miscible liquid

When falling in a lighter miscible solvent, a drop of liquid deforms to a torus which then breaks up into several fragments or just disappears by diffusion. By using liquids of different compositions we show the universal behaviour of the phenomenon, and its dependence on two nondimensional numbers, the fragmentation number F, and the Schmidt number S. While F marks the transition from diffusion to splitting, here we show the role of S in controlling the number of horizontal fragments after the first break-up. The process is explained in terms of competitions of different time scales

Fatigue performance of thermally cut bolt holes in structural steel S460M

Current fatigue codes only consider the fatigue performance of drilled and punched holes, limiting the use of thermal cutting processes to produce bolt holes. This paper studies the fatigue performance of structural steel S460M plates containing thermally cut bolt holes. The research covers three thermal cutting methods: the traditional one (oxy-fuel cutting) and two more modern processes (plasma and laser cutting). Specimen geometry is defined by a rectangular cross section with a cut hole in the middle. All the specimens were conducted to failure by applying fatigue cycles, the stress ratio (R) being 0.1. The corresponding S-N curve and fatigue limit were obtained for each cutting method. Fatigue results have been compared with previous researches on fatigue performance of drilled and punched holes, and with the predictions provided by current fatigue standards, analyzing the possibility to extrapolate their S-N curves, focused on drilled and punched holes, to thermally cut holes

The industrial production of dimethyl carbonate from methanol and carbon dioxide

This work discusses the design of a dimethyl carbonate (DMC) production plant based on methanol and CO2 as feed materials, which are a cheap and environment-friendly feedstock. DMC is a good alternative for methyl-tert-butyl ether (MTBE) as a fuel oxygenating agent, due to its low toxicity and fast biodegradability. Based on the MTBE demand of a general gasoline plant, the annual production capacity of the process design is stipulated to be 86 kt DMC, with a purity of 99 wt%. Three routes are proposed to form DMC: 1) direct synthesis from methanol and CO2, 2) reaction of CO2 and ammonia to urea, which can be converted to DMC with methanol, 3) reaction of ethylene oxide with CO2 to a cyclic carbonate, which can be converted to DMC by transesterification with methanol. From a black box cost analysis based on raw material prices, it is concluded that the ethylene oxide route is the least profitable. Because of higher single-pass conversions found in literature, smaller recycles and easier separations, it is concluded that the urea route would be the most feasible. The required process functions for the urea route have been determined in the conceptual design phase. A detailed design of the most important process operations is made and an overall technical and economic evaluation of the process has been carried out. In the first step of this DMC synthesis, urea is produced from carbon dioxide and ammonia with the ACES21 process. After separation and purification steps, urea is fed to a reactor with methanol (150 °C, 20 bar), where methyl carbamate (MC), an intermediate of DMC production, and ammonia are formed in the absence of a catalyst. Subsequently, MC and methanol are converted to DMC and ammonia (190 °C, 40 bar) over a ZnO-Al2O3 catalyst in a fixed-bed reactor. Methanol and DMC form an azeotrope; extractive distillation with methyl isobutyl ketone (MIBK) as entrainer is used to separate the azeotropic mixture. The reactor model for the reaction towards DMC based on kinetic rate expressions, showed that a long residence time (>10 h) and a relatively high MeOH:MC molar feed ratio of 6 are required to achieve reasonable single-pass conversions (15 %). This resulted however in an unrealistically large reactor volume and a large methanol load on the process. A feasibility study was done in order to improve the performance of the process. It was calculated that with a MeOH:MC ratio of 2 and a single-pass conversion of MC of 30 % the process would become technically feasible; the reactor volume decreased from 5,000 m3 to 600 m3 and the energy consumption of the process was decreased from 238 MW to 50 MW. A Pinch analysis showed that maximally 6 MW could be saved with heat integration, which corresponds to approximately 2 M$/y savings on energy costs. To produce 86 kt/y of DMC, the required amounts of raw materials are 80 kt/y of methanol and 58 kt/y of CO2, which results in an overall DMC yield from methanol of 38$. Economic feasibility depends on the DMC selling price. A price range between 800 and 1,100 $/t was assumed. For 800$/t it is not possible to repay the capital investment within an assumed lifetime of 10 years and the process would therefore not be profitable. The break-even point is at 845 $/t. For a selling price of 1,100$/t the gross profit becomes 22 M$/y, with a payback period of 3 years and a return on investment of 20 %

Fluctuations and Dissipation of Coherent Magnetization

A quantum mechanical model is used to derive a generalized Landau-Lifshitz equation for a magnetic moment, including fluctuations and dissipation. The model reproduces the Gilbert-Brown form of the equation in the classical limit. The magnetic moment is linearly coupled to a reservoir of bosonic degrees of freedom. Use of generalized coherent states makes the semiclassical limit more transparent within a path-integral formulation. A general fluctuation-dissipation theorem is derived. The magnitude of the magnetic moment also fluctuates beyond the Gaussian approximation. We discuss how the approximate stochastic description of the thermal field follows from our result. As an example, we go beyond the linear-response method and show how the thermal fluctuations become anisotropy-dependent even in the uniaxial case.Comment: 22 page

Block Spin Density Matrix of the Inhomogeneous AKLT Model

We study the inhomogeneous generalization of a 1-dimensional AKLT spin chain model. Spins at each lattice site could be different. Under certain conditions, the ground state of this AKLT model is unique and is described by the Valence-Bond-Solid (VBS) state. We calculate the density matrix of a contiguous block of bulk spins in this ground state. The density matrix is independent of spins outside the block. It is diagonalized and shown to be a projector onto a subspace. We prove that for large block the density matrix behaves as the identity in the subspace. The von Neumann entropy coincides with Renyi entropy and is equal to the saturated value.Comment: 20 page

¿Cómo diseñar, aplicar y evaluar un programa de Mentoring en enfermedad renal crónica? evaluación narrativa del impacto en 6 centros asistenciales

Antecedentes y objetivo La enfermedad renal crónica (ERC) requiere de un proceso de adaptación en el paciente, que se puede facilitar con el apoyo de los profesionales sanitarios, así como por iguales capacitados. El objetivo de este estudio es presentar la puesta en marcha de un programa piloto de paciente mentor para promover la adaptación de los pacientes con ERC. Materiales y método Diseño mixto (cuantitativo y cualitativo) pre-post. El estudio se llevó a cabo en 6 hospitales de España. Los instrumentos utilizados para medir el impacto fueron escalas elaboradas ad-hoc (formato de respuesta escala de Likert de 10 puntos) de satisfacción y adquisición de competencias, así como la creación de grupos focales con 8 pacientes mentores y 10 profesionales sanitarios. Se dividió el programa en 4 fases: 1) Diseño y validación de contenidos del programa manualizado y selección de pacientes mentores; 2) Formación a mentores, satisfacción con la formación y competencias adquiridas por los mentores; 3) Implementación de los grupos de apoyo mutuo y perfil de los asistentes a los grupos de apoyo mutuo, y 4) Evaluación y resultados del programa de Mentoring. Resultados Se han formado a un total de 39 mentores en habilidades para conducción de grupos, así como para facilitar apoyo emocional. Se han conducido 22 grupos de apoyo con 121 participantes (22% cuidadores). El 65% de los pacientes estaban en consulta de ERC. Un 65% de los pacientes participantes consideraron hacer algún cambio en su estilo de vida tras la asistencia al programa. Todos los ítems que evalúan satisfacción y utilidad han mostrado una puntuación muy elevada, por encima del valor 8, 5 sobre 10. Conclusiones Este es el primer programa manualizado de Mentoring en ERC llevado a cabo de manera simultánea en 6 hospitales españoles. La naturaleza del programa, manualizado y altamente estructurado, permite su replicabilidad minimizando el riesgo de error. Background and objective Chronic kidney disease (CKD) requires patients to participate in an adaptation process, which may be facilitated with the support of healthcare professionals and trained peers. The objective of this study is to present the implementation of a pilot patient mentoring programme to promote adaptation in patients with CKD. Materials and method Pre-test-post-test design (quantitative and qualitative). The study was carried out in six hospitals in Spain. The instruments used to measure impact were ad-hoc scales (10-point Likert scale response format) on satisfaction and skill acquisition, as well as the creation of focus groups with eight patient mentors and 10 healthcare professionals. The programme was split into four phases: 1. Design and validation of the manualised programme''s content, and selection of patient mentors; 2. Mentor training, satisfaction with training and skills acquired by the mentors; 3. Implementation of mutual support groups and profile of those attending these mutual support groups; 4. Assessment and results of the Mentoring programme. Results In total, 39 mentors were trained on group management skills, as well as how to provide emotional support. 22 support groups were held, with 121 participants (22% carers). The 65% of the patients were attending the CKD clinic. 65% of the participating patients considered making some form of lifestyle change after taking part in the programme. All the items assessing satisfaction and usefulness scored very highly, achieving 8.5 out of 10 or above. Conclusions This is the first manualised mentoring programme in CKD to be undertaken simultaneously in six Spanish hospitals. The manualised and highly structured nature of the programme make it easy to replicate, minimising the risk of error

Entanglement and Density Matrix of a Block of Spins in AKLT Model

We study a 1-dimensional AKLT spin chain, consisting of spins $S$ in the bulk and $S/2$ at both ends. The unique ground state of this AKLT model is described by the Valence-Bond-Solid (VBS) state. We investigate the density matrix of a contiguous block of bulk spins in this ground state. It is shown that the density matrix is a projector onto a subspace of dimension $(S+1)^{2}$. This subspace is described by non-zero eigenvalues and corresponding eigenvectors of the density matrix. We prove that for large block the von Neumann entropy coincides with Renyi entropy and is equal to $\ln(S+1)^{2}$.Comment: Revised version, typos corrected, references added, 31 page