Modern Migration in Ghana and Mali: A Comparison of Urban Migration Patterns

West Africa has a long tradition of human migration. Since the era of European colonization and during the twentieth century much of this migration has been rural to urban. This paper analyzes statistical data, observations, and interviews to compare the impacts of this migration on the cities of Bamako, Mali and Accra, Ghana. This analysis supports the conclusions that rural to urban migration in Ghana has resulted in the creation of an urban subsistence existence and an increased number of people participating in the informal sector of the economy. It further shows that when compared with Ghana, internal migration patterns and factors in Mali have resulted in much less growth in the urban population and informal sector of the economy. It appears that the people of Mali continue to prefer to engage in subsistence agriculture rather than to shift to a subsistence urban existence

A robust two-node, 13 moment quadrature method of moments for dilute particle flows including wall bouncing

For flows where the particle number density is low and the Stokes number is relatively high, as found when sand or ice is ingested into aircraft gas turbine engines, streams of particles can cross each other’s path or bounce from a solid surface without being influenced by inter-particle collisions. The aim of this work is to develop an Eulerian method to simulate these types of flow. To this end, a two-node quadrature-based moment method using 13 moments is proposed. In the proposed algorithm thirteen moments of particle velocity, including cross-moments of second order, are used to determine the weights and abscissas of the two nodes and to set up the association between the velocity components in each node. Previous Quadrature Method of Moments (QMOM) algorithms either use more than two nodes, leading to increased computational expense, or are shown here to give incorrect results under some circumstances. This method gives the computational efficiency advantages of only needing two particle phase velocity fields whilst ensuring that a correct combination of weights and abscissas are returned for any arbitrary combination of particle trajectories without the need for any further assumptions. Particle crossing and wall bouncing with arbitrary combinations of angles are demonstrated using the method in a two-dimensional scheme. The ability of the scheme to include the presence of drag from a carrier phase is also demonstrated, as is bouncing off surfaces with inelastic collisions. The method is also applied to the Taylor-Green vortex flow test case and is found to give results superior to the existing two-node QMOM method and in good agreement with results from Lagrangian modelling of this case

Standards of Best Practices Environmental Education & Interpretation Professionals

This document provides guidelines about the knowledge and skills needed to provide effective Environmental Education and Interpretation (EE&I) experiences in the state of Nevada. Effective experiences not only further the mission of the organization but also inspire understanding, appreciation, and stewardship of Southern Nevada’s environment. Standards of Best Practices for Nevada Environmental Education & Interpretation (NEE&I) Professionals is a guide for providers working at public lands, nature centers, museums, zoos, aquaria, schools, and all nature and heritage-rich places. It is designed to help NEE&I providers develop and implement the highest quality experiences for all possible audiences. It is a tool for NEE&I providers to use as they develop new experiences, deliver programs, or evaluate the effectiveness of the experience. Because EE&I experiences come in many forms, not every part of this document will apply to every EE&I experience

SME: Scalable Masking Extensions

Supporting masking countermeasures for non-invasive side-channel security in instructions set architectures is a hard problem. Masked operations often have a large number of inputs and outputs, and enabling portable higher order masking has remained a difficult. However, there are clear benefits to enabling this in terms of performance, code density and security guarantees. We present SME, an instruction set extension for enabling secure and efficient software masking of cryptographic code at higher security orders. Our design improves on past work by enabling the same software to run at higher masking orders, depending on the level of security the CPU/SoC implementer has deemed appropriate for their product or device at design time. Our approach relies on similarities between implementations of higher order masking schemes and traditional vector programming. It greatly simplifies the task of writing masked software, and restores the basic promise of ISAs: that the same software will run correctly and securely on any correctly implemented CPU with the necessary security guarantees. We describe our concept as a custom extension to the RISC-V ISA, and its soon to be ratified scalar cryptography extension. An example implementation is also described, with performance and area tradeoffs detailed for several masking security orders. To our knowledge, ours is the first example of enabling flexible side-channel secure implementations of the official RISC-V lightweight cryptography instructions

Simulation of particle flow in an inertial particle separator with an Eulerian velocity re-associated two-node quadrature-based method of moments

This paper presents research into practical simulations of particle flow in inertial particle separators (IPS) for helicopters and tilt rotor aircraft. The flow field of the carrier gas is predicted by means of the two-equation k-ϵ turbulence model. An Eulerian methodology is used to trace the particle trajectories of foreign particles such as droplets, ice and sand. To predict the characteristics of particle wall bouncing in dilute particle flow, the velocity re-associated two-node quadrature-based method of moments (VR-QMOM) is used. The particle distribution in the IPS is predicted for various particle sizes and these are compared with results from a Lagrangian particle tracking method. The particle-wall interactions and the separation efficiencies are studied for solid particles bouncing off perfectly elastic walls and an IPS shell coated with the M246 alloy which changes the coefficients of restitution. The simulated separation efficiencies predicted by the Eulerian method are compared with the simulation using the Lagrangian method over a range of particle sizes. The VR-QMOM method is seen to reproduce the particle bouncing and trajectory crossing behavior and to agree well with the Lagrangian method for predicted separation efficiencies. The new VR-QMOM method is shown to be an accurate and convenient alternative to established Lagrangian approaches

Performance, Politics and Media: How the 2010 British General Election leadership debates generated ‘talk’ amongst the electorate.

During the British General Election 2010 a major innovation was introduced in part to improve engagement: a series of three live televised leadership debates took place where the leader of each of the three main parties, Labour, Liberal Democrat and Conservative, answered questions posed by members of the public and subsequently debated issues pertinent to the questions. In this study we consider these potentially ground breaking debates as the kind of event that was likely to generate discussion. We investigate various aspects of the ‘talk’ that emerged as a result of watching the debates. As an exploratory study concerned with situated accounts of the participants experiences we take an interpretive perspective. In this paper we outline the meta-narratives (of talk) associated with the viewing of the leadership debates that were identified, concluding our analysis by suggesting that putting a live debate on television and promoting and positioning it as a major innovation is likely to mean that is how the audience will make sense of it – as a media event

Efficient Modular Multiplication

This paper is concerned with one of the fundamental building blocks used in modern public-key cryptography: modular multiplication. Speed-ups applied to the modular multiplication algorithm or implementation directly translate in a faster modular exponentiation for RSA or a faster realization of the group law when using elliptic curve cryptography

Children are important too:juvenile playgroups and maternal childcare in a foraging population, the Agta

Non-maternal carers (allomothers) are hypothesized to lighten the mother's workload, allowing for the specialized human life history including relatively short interbirth intervals and multiple dependent offspring. Here, using in-depth observational data on childcare provided to 78 Agta children (a foraging population in the northern Philippines; aged 0-6 years), we explore whether allomaternal childcare substitutes and decreases maternal childcare. We found that allomother caregiving was associated with reduced maternal childcare, but the substitutive effect varied depending on the source and type of care. Children-only playgroups consistently predicted a decrease in maternal childcare. While grandmothers were rarely available, their presence was negatively associated with maternal presence and childcare, and grandmothers performed similar childcare activities to mothers. These results underscore the importance of allomothering in reducing maternal childcare in the Agta. Our findings suggest that flexibility in childcare sources, including children-only playgroups, may have been the key to human life-history evolution. Overall, our results reinforce the necessity of a broad conceptualization of social support in human childcare. This article is part of the theme issue 'Multidisciplinary perspectives on social support and maternal-child health'

Children are important too: juvenile playgroups and maternal childcare in a foraging population, the Agta

Non-maternal carers (allomothers) are hypothesized to lighten the mother's workload, allowing for the specialized human life history including relatively short interbirth intervals and multiple dependent offspring. Here, using in-depth observational data on childcare provided to 78 Agta children (a foraging population in the northern Philippines; aged 0–6 years), we explore whether allomaternal childcare substitutes and decreases maternal childcare. We found that allomother caregiving was associated with reduced maternal childcare, but the substitutive effect varied depending on the source and type of care. Children-only playgroups consistently predicted a decrease in maternal childcare. While grandmothers were rarely available, their presence was negatively associated with maternal presence and childcare, and grandmothers performed similar childcare activities to mothers. These results underscore the importance of allomothering in reducing maternal childcare in the Agta. Our findings suggest that flexibility in childcare sources, including children-only playgroups, may have been the key to human life-history evolution. Overall, our results reinforce the necessity of a broad conceptualization of social support in human childcare. This article is part of the theme issue ‘Multidisciplinary perspectives on social support and maternal–child health’

Automatic Insertion of DPA Countermeasures

Differential Power Analysis (DPA) attacks find a statistical correlation between the power consumption of a cryptographic device and intermediate values within the computation. Randomization of intermediate values breaks statistical dependence and thus prevents such attacks. The current state of the art in countermeasures involves manual manipulation of low-level assembly language to insert random masking. This paper introduces an algorithm to automate the process allowing the development of compilers capable of protecting programs against DPA