Safer typing of complex API usage through Java generics

When several incompatible implementations of a single API are in use in a Java program, the danger exists that instances from different implementations may inadvertently be mixed, leading to errors. In this paper we show how to use generics to prevent such mixing. The core idea of the approach is to add a type parameter to the interfaces of the API, and tie the classes that make up an implementation to a unique choice of type parameter. In this way methods of the API can only be invoked with arguments that belong to the same implementation. We show that the presence of a type parameter in the interfaces does not violate the principle of interface-based programming: clients can still completely abstract over the choice of implementation. In addition, we demonstrate how code can be reused between different implementations, how implementations can be defined as extensions of other implementations, and how different implementations may be mixed in a controlled and safe manner. To explore the feasibility of the approach, gauge its usability, and identify any issues that may crop up in practical usage, we have refactored a fairly large existing API-based application suite, and we report on the experience gained in the process

Fully Constrained Majorana Neutrino Mass Matrices Using Σ(72×3)\Sigma(72\times 3)

In 2002, two neutrino mixing ansatze having trimaximally-mixed middle ($\nu_2$) columns, namely tri-chi-maximal mixing ($\text{T}\chi\text{M}$) and tri-phi-maximal mixing ($\text{T}\phi\text{M}$), were proposed. In 2012, it was shown that $\text{T}\chi\text{M}$ with $\chi=\pm \frac{\pi}{16}$ as well as $\text{T}\phi\text{M}$ with $\phi = \pm \frac{\pi}{16}$ leads to the solution, $\sin^2 \theta_{13} = \frac{2}{3} \sin^2 \frac{\pi}{16}$, consistent with the latest measurements of the reactor mixing angle, $\theta_{13}$. To obtain $\text{T}\chi\text{M}_{(\chi=\pm \frac{\pi}{16})}$ and $\text{T}\phi\text{M}_{(\phi=\pm \frac{\pi}{16})}$, the type~I see-saw framework with fully constrained Majorana neutrino mass matrices was utilised. These mass matrices also resulted in the neutrino mass ratios, $m_1:m_2:m_3=\frac{\left(2+\sqrt{2}\right)}{1+\sqrt{2(2+\sqrt{2})}}:1:\frac{\left(2+\sqrt{2}\right)}{-1+\sqrt{2(2+\sqrt{2})}}$. In this paper we construct a flavour model based on the discrete group $\Sigma(72\times 3)$ and obtain the aforementioned results. A Majorana neutrino mass matrix (a symmetric $3\times 3$ matrix with 6 complex degrees of freedom) is conveniently mapped into a flavon field transforming as the complex 6 dimensional representation of $\Sigma(72\times 3)$. Specific vacuum alignments of the flavons are used to arrive at the desired mass matrices.Comment: 20 pages, 1 figure. arXiv admin note: substantial text overlap with arXiv:1402.085

Deviations from Tribimaximal Neutrino Mixing using a Model with Δ(27)\Delta(27) Symmetry

We present a model of neutrino mixing based on the flavour group $\Delta(27)$ in order to account for the observation of a non-zero reactor mixing angle ($\theta_{13}$). The model provides a common flavour structure for the charged-lepton and the neutrino sectors, giving their mass matrices a `circulant-plus-diagonal' form. Mass matrices of this form readily lead to mixing patterns with realistic deviations from tribimaximal mixing, including non-zero $\theta_{13}$. With the parameters constrained by existing measurements, our model predicts an inverted neutrino mass hierarchy. We obtain two distinct sets of solutions in which the atmospheric mixing angle lies in the first and the second octants. The first (second) octant solution predicts the lightest neutrino mass, $m_3 \sim 29~\text{meV}$ ($m_3 \sim 65~\text{meV}$) and the $CP$ phase, $\delta_{CP} \sim -\frac{\pi}{4}$ ($\delta_{CP} \sim \frac{\pi}{2}$), offering the possibility of large observable $CP$ violating effects in future experiments.Comment: 9 pages, 3 figure

Systems simulations supporting NASA telerobotics

Two simulation and analysis environments have been developed to support telerobotics research at the Langley Research Center. One is a high-fidelity, nonreal-time, interactive model called ROBSIM, which combines user-generated models of workspace environment, robots, and loads into a working system and simulates the interaction among the system components. Models include user-specified actuator, sensor, and control parameters, as well as kinematic and dynamic characteristics. Kinematic, dynamic, and response analyses can be selected, with system configuration, task trajectories, and arm states displayed using computer graphics. The second environment is a real-time, manned Telerobotic Systems Simulation (TRSS) which uses the facilities of the Intelligent Systems Research Laboratory (ISRL). It utilizes a hierarchical structure of functionally distributed computers communicating over both parallel and high-speed serial data paths to enable studies of advanced telerobotic systems. Multiple processes perform motion planning, operator communications, forward and inverse kinematics, control/sensor fusion, and I/O processing while communicating via common memory. Both ROBSIM and TRSS, including their capability, status, and future plans are discussed. Also described is the architecture of ISRL and recent telerobotic system studies in ISRL

EXIST: Mission Design Concept and Technology Program

The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed very large area coded aperture telescope array, incorporating 8m^2 of pixellated Cd-Zn-Te (CZT) detectors, to conduct a full-sky imaging and temporal hard x-ray (10-600 keV) survey each 95min orbit. With a sensitivity (5sigma, 1yr) of ~0.05mCrab (10-150 keV), it will extend the ROSAT soft x-ray (0.5-2.5keV) and proposed ROSITA medium x-ray (2-10 keV) surveys into the hard x-ray band and enable identification and study of sources ~10-20X fainter than with the ~15-100keV survey planned for the upcoming Swift mission. At ~100-600 keV, the ~1mCrab sensitivity is 300X that achieved in the only previous (HEAO-A4, non-imaging) all-sky survey. EXIST will address a broad range of key science objectives: from obscured AGN and surveys for black holes on all scales, which constrain the accretion history of the universe, to the highest sensitivity and resolution studies of gamma-ray bursts it will conduct as the Next Generation Gamma-Ray Burst mission. We summarize the science objectives and mission drivers, and the results of a mission design study for implementation as a free flyer mission, with Delta IV launch. Key issues affecting the telescope and detector design are discussed, and a summary of some of the current design concepts being studied in support of EXIST is presented for the wide-field but high resolution coded aperture imaging and very large area array of imaging CZT detectors. Overall mission design is summarized, and technology development needs and a development program are outlined which would enable the launch of EXIST by the end of the decade, as recommended by the NAS/NRC Decadal Survey.Comment: 14 pages, 8 figures, 2 tables. PDF file only. Presented at SPIE (Aug. 2002) and to appear in Proc. SPIE, vol. 485

Rules of thumb for evaluating preferential trading arrangements : evidence from computable general equilibrium assessments

Most interesting results on the welfare effects of regional arrangements are ambiguous at a theoretical level. Many questions only have quantitative answers that are specific to the particular structural features of the economy and the policy considered. So, to determine the impact of prospective regional arrangements governments often rely on a quantitative evaluation. Usually at the request of client governments of the World Bank, the authors have implemented many computable general equilibrium (CGE) models to inform policymakers. The authors summarize the main conclusions drawn from these studies. The principal conclusions are: 1) Countries excluded from a preferential trade arrangement almost always lose. 2) Market access is a key determinant of the net benefits of a preferential trade arrangement. 3) With a free trade agreement (FTA) the external tariff can be lowered such that a poor FTA becomes attractive. 4) For Southern countries, North-South agreements offer a beneficial increase in competition in their home markets, and involve little increase in the supply price of Northern country sales in Southern countries. 5) Multilateral trade liberalization results in significantly larger gains to the world than the network of regional arrangements. 6) For individual countries without high protection,"additive regionalism"will likely result in substantially larger gains than unilateral trade liberalization. 7) Tax replacement requirements reduce the set of desirable regional arrangements. 8) Trade taxes are often an inefficient source of tax revenue. 9) Trade liberalization should be expected to be pro-poor in developing countries, but results will be diverse at the household level so safety nets are important. 10) Dynamic effects to reverse conclusions regarding regionalism are not expected.Environmental Economics&Policies,Payment Systems&Infrastructure,Economic Theory&Research,Trade Policy,Rules of Origin,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Trade and Regional Integration,Environmental Economics&Policies,Economic Theory&Research,Trade Policy

Cloud parameters from GOES visible and infrared radiances during the FIRE Cirrus IFO, October 1986

Visible (VIS, 0.65 micron) and infrared (IR, 10.5 microns) channels on geostationary satellites are the key elements of the International Satellite Cloud Climatology Project (ISCCP). All daytime ISCCP cloud parameters are derived from a combination of VIS and IR data. Validation and improvement of the ISCCP and other cloud retrieval algorithms are important components of the First ISCCP Regional Experiment (FIRE) Intensive Field Observations (IFO). Data from the Cirrus IFO (October 19 to November 2, 1986) over Wisconsin are available for validating cirrus cloud retrievals from satellites. The Geostationary Operational Environmental Satellite (GOES) located over the Equator at approximately 100 deg W provided nearly continuous measurements of VIS and IR radiances over the IFO areas. The preliminary results of cloud parameters derived from the IFO GOES data are presented. Cloud attitudes are first derived using an algorithms without corrections for cloud emissivity. These same parameters will then be computed from the same data relying on an emissivity correction algorithm based on correlative data taken during the Cirrus IFO

Economic implications for Turkey of a customs union with the European Union

Turkey and the European Union (EU) have agreed to implement a customs union. This means Turkey will eliminate its tariffs and levies on imports on manufactured products from the EU. Turkey will also apply EU's"common external tariff"on imports from third countries. Turkey will be obligated by 20001 to provide preferential access to its markets to all countries to which the EU grants such access. Since Turkey is both eliminating tariffs on EU imports and reducing tariffs on imports from third countries, it will become a rather open economy in nonagricultural sectors. And since preferential access agreements with third countries will typically be reciprocal, Turkish exporters can expect improved access to those markets. According to the authors, Turkey's biggest gains from the customs union arrangement will come from this improved access to third country markets. Using a comparative static computable general equilibrium model of Turkey, they estimate that Turkey stands to gain between 1 and 1.5 percent of gross domestic product (GDP) annually from the customs union arrangement with the EU, depending on what complementary policies it adopts. They also estimate that lost tariff revenues will amount to 1.4 percent of GDP. For Turkey to avoid worsening its fiscal deficit, it must find ways to reduce expenditures or increase revenues. Its best choice is to reduce expenditures through accelerating privatization of state-owned enterprises which will generate a number of macroeconomic and efficiency benefits in addition to the fiscal benefits. If a value-added tax (VAT) is used as a replacement tax, they estimate that VAT rates must increase 16.2 percent in each sector to compensate for the revenue losses from implementing the full customs union. But uniform application of the VAT would allow the VAT rates to fall while still compensating for the loss from reduced tariffs and would increase the welfare gain from the customs union.Economic Theory&Research,Environmental Economics&Policies,Trade Policy,Export Competitiveness,Trade Finance and Investment,Trade and Regional Integration,Trade Policy,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Environmental Economics&Policies

Piecemeal trade reform in partially liberalized economies : an evaluation for Turkey

Turkey undertook a major liberalization of trade policy in the 1980s. Import quotas disappeared, the Turkish lira was made convertible, and tariffs are generally lower. Those changes and the export subsidies that remain have removed the anti-export bias from Turkey's external incentive regime. Using a 40-sector computable general equilibrium model, the authors consider several more trade liberalization options available to the Turkish government. They conclude that uniformity of tariffs and export subsidies would substantially improve Turkey's welfare. Although the"Ramsey"optimal import taxation would call for non-uniform import taxes inversely proportional to the elasticity of import demand in each sector, the observed dispersion of tariff structure in Turkey is inconsistent with optimal departures from uniform protection. In fact, uniformity achieves an extremely high proportion of the benefits of full trade liberalization because, in the absence of a general anti-export bias, theprincipal distortion remaining in the trade regime derives from dispersion of the tariff and, especially the export subsidy structure. An increasing number of developing countries - including Chile, Indonesia, Mexico, and Poland - have in recent years undertaken extensive trade liberalization. It is no longer clear that these economies retain an anti-export bias in their trade regime. Perhaps the most important policy conclusion the authors reach is that one must be wary of advocating piecemeal reform of tariffs or export subsidies alone. Piecemeal across-the-board tariff reductions do not always improve welfare; they must generally be coordinated with reductions in export subsidies to ensure improved welfare. The authors counterfactually assume that Turkey's tariffs are at the 1985 level which reintroduces an anti-export bias of import tariffs. In this case, piecemeal tariff reduction to the 1989 level is beneficial. Even small export subsidies are not always beneficial, despite the rule of thumb that small export subsidies are a welfare-enhancing offset to the anti-export bias of import tariffs. Export subsidies in Turkey are highly dispersed, and piecemeal reductions in the export subsidies reduce that dispersion. When the authors counterfactually impose uniformity of tariffs and export subsidies, they note that small export subsidies are beneficial as a piecemeal policy for offsetting the anti-export bias. Policymakers in developing countries have occasionally applied export subsidies in individual sectors with high tariffs as a means of encouraging exports in a sector that may otherwise rely on the highly protected domestic market. The authors show that in Turkey high export subsidies in sectors with high tariffs are particularly counterproductive - because at the multisector level the distortion introduced by the export subsidy dominates the reduction in anti-export bias. Turkey's proposed policy of harmonizing its tariff to the European Community's (EC's) common external tariff would yield only small welfare changes. Harmonizing the EC tariffs will require lowering tariffs below already low levels, in the presence of export subsidies almost as large as the existing average effective tariff rate. However harmonizing to the EC tariff structure can be beneficial if at the same time export subsidies are removed or reduced.Environmental Economics&Policies,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Tax Law,Trade Policy