Numerical simulation of free surface behaviour of a molten liquid metal droplet with and without electromagnetic induction

Electromagnetic levitation of electrically conductive droplets by alternating magnetic fields is a technique used to measure the physical properties of liquid metallic alloys such as surface tension or viscosity. Experiments can be conducted under terrestrial conditions or in microgravity, to reduce electromagnetic stirring and shaping of the droplet. Under such conditions, the time-dependent behaviour of a point of the free surface is recorded. Then the signal is analysed considering the droplet as a harmonic damped oscillator. We use a spectral code, for fluid flow and free surface descriptions, to check the validity of this assumption for two cases. First when the motion inside the droplet is generated by its initial distortion only and second, when the droplet is located in a uniform magnetic field originating far from the droplet. It is found that some deviations exist which can lead to an overestimate of the value of viscosity.

The study of flow and temperature fields in conducting droplets suspended in a DC/AC combination field

Electromagnetic Levitation (EML) is a valuable method for measuring the thermo-physical properties of metals - surface tensions, viscosity, thermal/electrical conductivity, specific heat, hemispherical emissivity, etc. – beyond their melting temperature. In EML, a small amount of the test specimen is melted by Joule heating in a suspended AC coil. Once in liquid state, a small perturbation causes the liquid envelope to oscillate and the frequency of oscillation is then used to compute its surface tension by the well know Rayleigh formula. Similarly, the rate at which the oscillation is dampened relates to the viscosity. To measure thermal conductivity, a sinusoidally varying laser source may be used to heat the polar axis of the droplet and the temperature response measured at the polar opposite – the resulting phase shift yields thermal conductivity. All these theoretical methods assume that convective effects due to flow within the droplet are negligible compared to conduction, and similarly that the flow conditions are laminar; a situation that can only be realised under microgravity conditions. Hence the EML experiment is the method favoured for Spacelab experiments (viz. TEMPUS). Under terrestrial conditions, the full gravity force has to be countered by a much larger induced magnetic field. The magnetic field generates strong flow within the droplet, which for droplets of practical size becomes irrotational and turbulent. At the same time the droplet oscillation envelope is no longer ellipsoidal. Both these conditions invalidate simple theoretical models and prevent widespread EML use in terrestrial laboratories. The authors have shown in earlier publications that it is possible to suppress most of the turbulent convection generated in the droplet skin layer, through use of a static magnetic field. Using a pseudo-spectral discretisation method it is possible compute very accurately the dynamic variation in the suspended fluid envelope and simultaneously compute the time-varying electromagnetic, flow and thermal fields. The use of a DC field as a dampening agent was also demonstrated in cold crucible melting, where suppression of turbulence was achieved in a much larger liquid metal volume and led to increased superheat in the melt and reduction of heat losses to the water-cooled walls. In this paper, the authors describe the pseudo-spectral technique as applied to EML to compute the combined effects of AC and DC fields, accounting for all the flow-induced forces acting on the liquid volume (Lorentz, Maragoni, surface tension, gravity) and show example simulations.

Effect of long-term aging on the rheological characteristics and printing performance of lead-free solder pastes used for flip-chip assembly

Stencil printing of solder pastes is a critical stage in the SMT assembly process as a high proportion of the solder-related defects can be attributed to this stage. As the trend towards product miniaturization continues, there is a greater need for better understanding of the rheological behaviour and printing performance of new paste formulations. This fundamental understanding is crucial for achieving the repeatable solder paste deposits from board-to-board and pad-to-pad required for more reliable solder interconnections. The paper concerns a study on the effect of ageing on the rheological characteristics and printing performance of new lead-free solder pastes formulations used for flip-chip assembly applications. The objective is to correlate the rheological characteristics of aged paste samples to their printing performance. The methodology developed can be used for bench-marking new lead-free paste formulations in terms of shelf life, the potential deterioration in rheological characteristics and their printing performance.

A review of some common Indo-Malayan and western Pacific species of Chthamalus barnacles (Crustacea: Cirripedia)

The type specimens of the common tropical intertidal barnacles Chthamalus malayensis and C. moro, were re-investigated and compared with other specimens of Chthamalus from the Indian Ocean, Indo-Malaya, northern Australia, Vietnam, China and the western Pacific, using ‘arthropodal’ as well as shell characters. Chthamalus malayensis occurs widely in Indo-Malayan and tropical Australian waters. It ranges westwards in the Indian Ocean to East Africa and northwards in the Pacific to Vietnam, China and the Ryukyu Islands. Chthamalus malayensis has the arthropodal characters attributed to it by Pope (1965); conical spines on cirrus 1 and serrate setae with basal guards on cirrus 2. Chthamalus moro is currently fully validated only for the Philippines, Indonesia, Taiwan, the Xisha (Paracel) Islands, the Ryukyu Islands, the Mariana Islands, the Caroline Islands, Fiji and Samoa. It is a small species of the ‘challengeri’ subgroup, lacking conical spines on cirrus 1 and bearing pectinate setae without basal guards on cirrus 2. It may be a ‘relict’ insular species. Chthamalus challengeri also lacks conical spines on cirrus 1 and has pectinate setae without basal guards on cirrus 2. Records of C. challengeri south of Japan are probably erroneous. However, there is an undescribed species of the ‘challengeri’ subgroup in the Indian Ocean, Indo-Malaya, Vietnam and southern China and yet more may occur in the western Pacific. The subgroups ‘malayensis’ and ‘challengeri’ require genetic investigation. Some comments are included on the arthropodal characters and geographical distributions of Chthamalus antennatus, C. dalli and C. stellatus

Discourses on Modernization in the Employment Public Services: Towards a New Form of Governance?

The “crisis of the social issue” in the EU has led to a certain consensus in the need to renew the organizational and institutional model of public administration. The core of the reform implies important administrative changes in most of the European welfare states. Those changes are inspired on theories such as the new public management, management by objectives or partnership. Such changes involve both semantic (“sharing responsibilities”, “effective costs”, or the substitution of “citizen under an administration” by “consumer”) and political (predominance of scattered forms of power and the individualization of responsibilities) transformations which operate in the framework of individuals and State relations. The paradigms of activation and flexicurity have been central in this public administration modernization project. This commitment with new forms of governance of social issues has important consequences for the political and moral foundations of social cohesion, and the Spanish case is not an exception. This paper aims at looking at those representations of “modernization” (as they appear in debates about the employment services restructuring policies) in detail as well as providing references to the trajectory of such reforms of public services since the early eighties to the beginning of the crisis.

Early Results of the 3mm Spectral Line Survey toward the L1157 B1 Shocked Region

We have conducted a sensitive 3mm observation toward the shocked region, Lynds 1157 B1, which is an interaction spot between a molecular outflow and its ambient gas. We have successfully detected the CH3CHO, HCOOCH3, and HCOOH lines, as well as the CH2DOH line. The abundances of these molecules relative to CH3OH are found to be lower than those in the low-mass star-forming core, IRAS 16293-2422. Since these molecules are thought to evaporate from grain mantles, the observational results mean that complex molecules are less abundant in grain mantles residing in the ambient cloud surrounding a prestellar/protostellar core. Instead, efficient formation of the complex organic species and deuterated species should take place in a prestellar/protostellar core. The present result verifies the importance of an unbiased line survey of this source.

A class of almost C_0(K)-C*-algebras

We consider in this paper the family of exponential Lie groups Gn,µ, whose Lie algebra is an extension of the Heisenberg Lie algebra by the reals and whose quotient group by the centre of the Heisenberg group is an ax + b-like group. The C*-algebras of the groups Gn,µ give new examples of almost C0(K)-C*-algebras.

A 1-D Vaneless Diffuser Model Accounting for the Effects of Spanwise Flow Stratification

The radial vaneless diffuser, though comparatively simple in terms of geometry, poses a significant challenge in obtaining an accurate 1-D based performance prediction due to the swirling, unsteady and distorted nature of the flow field. Turbocharger compressors specifically, with the ever increasing focus on achieving a wide operating range, have been recognised to operate with significant regions of spanwise separated flow, particularly at off design conditions.
Using a combination of single passage Computational Fluid Dynamics (CFD) simulations and extensive gas stand test data for three geometries, the current study aims to evaluate the onset and impact of spanwise flow stratification in radial vaneless diffusers, and how the extent of the aerodynamic blockage presented to the flow throughout the diffuser varies with both geometry and operating condition. Having analysed the governing performance parameters and flow phenomena, a novel 1-D modelling method is presented and compared to an existing baseline method as well as test data to quantify the improvement in prediction accuracy achieved.

Commemoration in the United Kingdom: A multitude of memories

In the United Kingdom (UK) the centenary commemoration of the First World War has been driven by a combination of central government direction (and funding) with a multitude of local and community initiatives, with a particular focus on 4 August 2014; 1 July 2016 (the beginning of the Battle of the Somme) and 11 November 2018. ‘National’ ceremonies on these dates have been and will be supplemented with projects commemorating micro-stories and government-funded opportunities for schoolchildren to visit Great War battlefields, the latter clearly aimed to reinforce a contemporary sense of civic and national obligation and service. This article explores the problematic nature of this approach, together with the issues raised by the multi-national nature of the UK state itself.

Remembering 1916: The Easter Rising, the Somme and the Politics of Memory in Ireland

The year 1916 witnessed two events that would profoundly shape both
politics and commemoration in Ireland over the course of the following
century. Although the Easter Rising and the Battle of the Somme were
important historical events in their own right, their significance also lay
in how they came to be understood as iconic moments in the emergence
of Northern Ireland and the Irish Republic. Adopting an interdisciplinary
approach drawing on history, politics, anthropology and cultural
studies, this volume explores how the memory of these two foundational
events has been constructed, mythologised and revised over the course
of the past century. The aim is not merely to understand how the Rising
and Somme came to exert a central place in how the past is viewed in
Ireland, but to explore wider questions about the relationship between
history, commemoration and memory.

The effect of frontal features on chlorophyll concentration within the Kuroshio

Senior thesis written for Oceanography 445

Imaginative Mislocation: Hiroshima’s Genbaku Dome, Ground Zero of the Twentieth Century

The controversy that erupted in March over the publication of Charles Pellegrino’s account of the atomic bombings of Japan, The Last Train from Hiroshima, suggests that the historical legacy of the first military use of atomic weaponry is still fiercely contested in the USA. The spat is merely the latest conflict in a long war over the significance of the bombings, which resurfaces with each new book, exhibition or programme that appears. When the ruins of the Genbaku (Atomic Bomb) Dome – formerly the Hiroshima Prefectural Commercial Exhibition Hall – were nominated as a UNESCO World Heritage Site in 1995, the United States objected on the basis of concerns over a ‘lack of historical perspective’, arguing that the ‘events antecedent to the United States’ use of atomic weapons to end World War II are key to understanding the tragedy of Hiroshima’. The appeal to historical facts by both US diplomats and, more recently, military veterans contrasts with the dehistoricized emphasis of other Western cultural responses to Hiroshima. But what both kinds of reception share is an occlusion of the prehistory of capitalist liberalism, colonialism and imperialism which produces Japanese modernity,a prehistory which is itself built into the Genbaku Dome’s concrete structure, and an afterlife of nuclear pacification which produces the global context of terrorism as the continuation of war by other means.

Application of adaptive neuro-fuzzy inference for wind power short-term forecasting

The increased integration of wind power into the electric grid, as nowadays occurs in Portugal, poses new challenges due to its intermittency and volatility. Hence, good forecasting tools play a key role in tackling these challenges. In this paper, an adaptive neuro-fuzzy inference approach is proposed for short-term wind power forecasting. Results from a real-world case study are presented. A thorough comparison is carried out, taking into account the results obtained with other approaches. Numerical results are presented and conclusions are duly drawn. (C) 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.