Automated parameters for troubled-cell indicators using outlier detection

In Vuik and Ryan (2014) we studied the use of troubled-cell indicators for discontinuity detection in nonlinear hyperbolic partial differential equations and introduced a new multiwavelet technique to detect troubled cells. We found that these methods perform well as long as a suitable, problem-dependent parameter is chosen. This parameter is used in a threshold which decides whether or not to detect an element as a troubled cell. Until now, these parameters could not be chosen automatically. The choice of the parameter has impact on the approximation: it determines the strictness of the troubled-cell indicator. An inappropriate choice of the parameter will result in detection (and limiting) of too few or too many elements. The optimal parameter is chosen such that the minimal number of troubled cells is detected and the resulting approximation is free of spurious oscillations. In this paper we will see that for each troubled-cell indicator the sudden increase or decrease of the indicator value with respect to the neighboring values is important for detection. Indication basically reduces to detecting the outliers of a vector (one dimension) or matrix (two dimensions). This is done using Tukey's boxplot approach to detect which coefficients in a vector are straying far beyond others (Tukey, 1977). We provide an algorithm that can be applied to various troubled-cell indication variables. Using this technique the problem-dependent parameter that the original indicator requires is no longer necessary as the parameter will be chosen automatically

Trade Reform and Poverty in the Philippines: a Computable General Equilibrium Microsimulation Analysis

The paper employs an integrated CGE-microsimulation approach to analyze the poverty effects of tariff reduction. The results indicate that the tariff cuts implemented between 1994 and 2000 were generally poverty-reducing, primarily through the substantial reduction in consumer prices they engendered. However, the reduction is much greater in the National Capital Region (NCR), where poverty incidence is already lowest, than in other areas, especially rural, where poverty incidence is highest. Tariff cuts lower the cost of local production and bring about real exchange rate depreciation. Since the non-food manufacturing sector dominates exports in terms of export share and export intensity, the general equilibrium effects of tariff reduction is an expansion of this sector and a contraction in the agricultural sector. This, in turn, leads to an increase in the relative returns to factors, such as capital, used intensively in the non-food manufacturing sector and a fall in returns to unskilled labor. As rural households depend more on unskilled labor income, income inequality worsens as a result.Dynamic CGE model, trade liberalisation, poverty, inequality, Senegal

Simulating Turbulence Using the Astrophysical Discontinuous Galerkin Code TENET

In astrophysics, the two main methods traditionally in use for solving the Euler equations of ideal fluid dynamics are smoothed particle hydrodynamics and finite volume discretization on a stationary mesh. However, the goal to efficiently make use of future exascale machines with their ever higher degree of parallel concurrency motivates the search for more efficient and more accurate techniques for computing hydrodynamics. Discontinuous Galerkin (DG) methods represent a promising class of methods in this regard, as they can be straightforwardly extended to arbitrarily high order while requiring only small stencils. Especially for applications involving comparatively smooth problems, higher-order approaches promise significant gains in computational speed for reaching a desired target accuracy. Here, we introduce our new astrophysical DG code TENET designed for applications in cosmology, and discuss our first results for 3D simulations of subsonic turbulence. We show that our new DG implementation provides accurate results for subsonic turbulence, at considerably reduced computational cost compared with traditional finite volume methods. In particular, we find that DG needs about 1.8 times fewer degrees of freedom to achieve the same accuracy and at the same time is more than 1.5 times faster, confirming its substantial promise for astrophysical applications.Comment: 21 pages, 7 figures, to appear in Proceedings of the SPPEXA symposium, Lecture Notes in Computational Science and Engineering (LNCSE), Springe

Doha scenarios, trade reforms, and poverty in the Philippines : a computable general equilibrium analysis

Since the early 1980s the Philippines has undertaken substantial trade reform. The current Doha Round of World Trade Organization (WTO) negotiations is now likely to bring further reform and shocks to world import prices and export demand. The impact of all these developments on the poor is not very clear and is the subject of intense debate. The authors use a detailed economywide computable general equilibrium (CGE) model to run a series of policy experiments. They find that poverty increases slightly with the implementation of the prospective Doha scenario. These effects are focused primarily among rural households in the wake of falling world prices and demand for the Philippines'agricultural exports. The authors find that the impacts of full liberalization-involving free world trade and complete domestic liberalization-depend strongly on the mechanism the government adopts to offset forgone tariff revenue. If an indirect tax is used, the incidence of poverty falls marginally, but the depth (poverty gap) and severity (squared poverty gap) increase substantially. If, instead, an income tax is used, all measures of poverty increase. In both cases, full liberalization favors urban households, as exports, which are primarily nonagricultural, expand. In separate simulations, the authors discover that free world trade is poverty reducing and favors rural households, whereas domestic liberalization is poverty increasing and favors urban households. Under free world trade, rural households benefit from increasing world agricultural demand. The anti-rural bias of domestic liberalization stems from the fact that import prices fall more for agricultural goods than for industrial goods, as initial import-weighted average tariff rates are higher for the former. In conclusion, the current Doha agreement appears likely to slightly increase poverty, especially in rural areas and among the unemployed, self-employed, and rural low-educated. The Philippines is found to have an interest in pushing for more ambitious world trade liberalization, as free world trade holds out promise for reducing poverty.

Fruits: their Forms and Modes Of Dispersal

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Doha scenarios, trade reforms, and poverty in the Philippines

"The paper examines the possible impact of Doha agreement on Philippine poverty. Using a detailed CGE analysis, the agreement is observed to depress world demand for Philippine agricultural exports, and thus slightly increase poverty, especially among rural households. However, an ambitious full trade liberalization scenario, which involves free world trade and domestic liberalization, leads to increased industrial exports that favor urban households. These impacts are driven primarily by domestic trade liberalization, as free world trade favors the agricultural sector by increasing the cost of competing agricultural imports." Authors' AbstractDoha agreement ,Computable general equilibrium (CGE) ,Free trade ,

Doha Scenarios, Trade Reforms, and Poverty inthe Philippines: a CGE Analysis

Since the early 1980s, the Philippines have undertaken substantial trade reform. The current Doha round of WTO negotiations is now likely to bring further reform and shocks to world import and export prices and world export demand. The impact of all these developments on the poor is not very clear and is the subject of very intense debate. A detailed economy-wide CGE model is used to run a series of policy experiments. Poverty is found to increase slightly with the implementation of the Doha scenario. These effects are focused primarily among rural households in the wake of falling world prices and demand for Philippines agricultural exports. The impacts of full liberalization involving free world trade and complete domestic liberalization are found to depend strongly on the mechanism the government adopts to offset forgone tariff revenue. If an indirect tax is used, the incidence of poverty falls marginally, but the depth (poverty gap) and severity (squared poverty gap) increase substantially. If, instead, an income tax is used, all measures of poverty increase. In both cases, full liberalization favors urban households, as exports, which are primarily non-agricultural, expand. In separate simulations, we discover that free world trade is poverty reducing and favors rural households, whereas domestic liberalization is poverty-increasing and favors urban households. Under free world trade, rural households benefit from increasing world agricultural export prices and demand. The anti-rural bias of domestic liberalization stems from the fact that import prices fall more for agricultural goods than for industrial goods, as initial import-weighted average tariffs rates are higher for the former. In conclusion, the current Doha agreement appears likely to slightly increase poverty, especially in rural areas and among the unemployed, self-employed and rural low-educated. The Philippines is found to have an interest in pushing for more ambitious world trade liberalization, as free world trade holds out promise for reducing poverty.Computable General Equilibrium, Microsimulation, Poverty, International Trade, Philippines

Historical roots of Agile methods: where did “Agile thinking” come from?

The appearance of Agile methods has been the most noticeable change to software process thinking in the last fifteen years [16], but in fact many of the “Agile ideas” have been around since 70’s or even before. Many studies and reviews have been conducted about Agile methods which ascribe their emergence as a reaction against traditional methods. In this paper, we argue that although Agile methods are new as a whole, they have strong roots in the history of software engineering. In addition to the iterative and incremental approaches that have been in use since 1957 [21], people who criticised the traditional methods suggested alternative approaches which were actually Agile ideas such as the response to change, customer involvement, and working software over documentation. The authors of this paper believe that education about the history of Agile thinking will help to develop better understanding as well as promoting the use of Agile methods. We therefore present and discuss the reasons behind the development and introduction of Agile methods, as a reaction to traditional methods, as a result of people's experience, and in particular focusing on reusing ideas from histor

Agricultural Price Distortions, Poverty and Inequality in the Philippines

This paper analyzes the poverty and inequality implications of removing agricultural and non-agricultural price distortions in the domestic market of the Philippines and abroad. Liberalization in the rest of the world is poverty and inequality reducing, whereas full domestic liberalization increases national poverty and inequality. Poverty declines while inequality increases marginally in the combined scenario of both global and domestic agriculture reform. Although the reduction in the national poverty headcount is small in the latter scenario, the poorest of the poor – particularly those living in the rural areas – emerge as “winners”, given their strong reliance on agricultural production and unskilled labor wages.Distorted incentives, agricultural and trade policy reforms, national agricultural development, Agricultural and Food Policy, International Relations/Trade, F13, F14, Q17, Q18,