Immigration Systems in Transition: Lessons for U.S. Immigration Reform from Australia and Canada

The history of both the Australian and Canadian immigration systems covers three distinct periods in which the countries maintained race-based models between the 1920s and 1960s-70s, implemented points-based systems after ending their race-based programs, and revised the points-based systems over time to improve their ability to select migrants and eliminate backlogs.Australia and Canada's successful implementation and revision of their immigration systems depended on governmental decisions, political and bureaucratic institutions, and data gathering operations to provide objective bases for revisions to the systems. The Australian and Canadian cases show that the United States may need to make investments in the agencies that oversee the immigration system and gather data about its outcomes. The adoption of SkillSelect and Express Entry also show that the United States may need to make dramatic revisions of the system to address backlogs and other residual components of the past system during the transition process. The effective selection of migrants and management of migration necessitates institutions that allow governments to make sometimes dramatic changes to their migration programs with public support based on actionable data. U.S. policymakers must understand these factors – and answer the questions in this report – to create an immigration system that represents the best elements of the U.S. political system and the country's immigration heritage

Coordinating Humanitarian Entry in the United States and Mexico: A Bilateral Approach to U.S. Legal Migration

Mexico and the United States have stated a joint interest in reducing illegal immigration through Mexico to the U.S.-Mexican border. Both countries are signatories of the Los Angeles Declaration on Migration and Protection, which pledges a coordinated multilateral approach to addressing migration, and Mexico has worked with the United States on its enforcement efforts, accepting returns from the United States. One untapped area of potential coordination is in each nation's authorization for migrants to temporarily enter their countries for humanitarian reasons.Unfortunately, the lack of coordination has meant that many migrants travel through Mexico and congregate in northern Mexico near the U.S.-Mexican border to try to obtain humanitarian entry into the United States. A better approach would be for Mexico to issue cards for visitors for humanitarian reasons at the Guatemalan??Mexican border, allowing migrants to travel to Mexico City, where they could apply for U.S. parole and fly directly to the United States legally

Management strategies for regional aiports: A study applied to Lleida- Alguaire Airport

Purpose: The main objective of this article is to analyse the current situation at Lleida-Alguaire Airport and propose possible actions to increase its profitability. Design/methodology/approach: This study presents the method as a research tool applied to regional airports, in particular, Lleida-Alguaire Airport. Findings: The study shows the importance of air transport and the current situation of Spanish airports, specifically in Catalonia, exposing the main air traffic imbalances between different airports and their effect on tourism. Finally, it describes and analyses the situation of Lleida-Alguaire Airport. Originality/value: This article is one of the first works to focus on regional airports and it seeks ways to improve their economic and social efficiency. Practical Implications: Some actions in relation with aeronautical traffic are presented in order to improve and increase the efficiency of the system

Polarized routing for large interconnection networks

Supercomputers and datacenters comprise hundreds of thousands of servers. Different network topologies have been proposed to attain such a high scalability, from flattened Butterfly and Dragonfly to the most disruptive Jellyfish, which is based on a random graph. The routing problem on such networks remains a challenge that can be tackled either as a topology-aware solution or with an agnostic approach. The case of random networks is a very special one since no a priori topological clues can be exploited. In this article, we introduce the polarized routing algorithm, an adaptive nonminimal hop-by-hop mechanism that can be used in most of topologies, including Jellyfish. Polarized routing follows two design criteria: a source-destination symmetry in the routes and avoiding backtracking. Experimental evaluation proves that polarized routing not only outperforms other routings in random graphs but also attains the best performance provided by ad hoc solutions for specific outstanding low-diameter interconnection networks.This work has been supported by the Spanish Ministry of Science and Innovation under contracts PID2019-105660RB-C22 and FJCI-2017-31643. Simulations were performed in the Altamira supercomputer, a node of the Spanish Super-computing Network

On random wiring in practicable folded clos networks for modern datacenters

Big scale, high performance and fault-tolerance, low-cost and graceful expandability are pursued features in current datacenter networks (DCN). Although there have been many proposals for DCNs, most modern installations are equipped with classical folded Clos networks. Recently, regular random topologies, as the Jellyfish, have been proposed for DCNs. However, their completely unstructured nature entails serious design problems. In this paper we propose Random Folded Clos (RFC) and Hydra networks in which the interconnection between certain switches levels is made randomly. Both RFCs and Hydras preserve important properties of Clos networks that provide a straightforward deadlock-free multi-path routing. The proposed networks leverage randomness to be gracefully expandable, thereby allowing for fine grain upgrading. RFCs and Hydras are compared in the paper, in topological and cost terms, against fat-trees, orthogonal fat-trees and random regular networks. Also, experiments are carried out to simulate their performance under synthetic traffic patterns emulating common loads present in warehouse scale computers. These theoretical and empirical studies reveal the interest of these topologies, concluding that Hydra constitutes a practicable alternative to current datacenter networks since it appropriately balance all the main design requirements. Moreover, Hydras perform better than the fat-trees, their natural competitor, being able to connect the same or more computing nodes with significant lower cost and latency while exhibiting comparable throughput. © 1990-2012 IEEE

Ant Mill: an adversarial traffic pattern for low-diameter direct networks

Since today’s HPC and data center systems can comprise hundreds of thousands of servers and beyond, it is crucial to equip them with a network that provides high performance. New topologies proposed to achieve such performance need to be evaluated under different traffic conditions, aiming to closely replicate real-world scenarios. While most optimizations should be guided by common traffic patterns, it is essential to ensure that no pathological traffic pattern can compromise the entire system. Determining synthetic adversarial traffic patterns for a network typically relies on a thorough understanding of its topology and routing. In this paper, we address the problem of identifying a generic adversarial traffic pattern for low-diameter direct interconnection networks. We first focus on Random Regular Graphs (RRGs), which represent a typical case for these networks. Moreover, RRGs have been proposed as topologies for interconnection networks due to their superior scalability and expandability, among other advantages. We introduce Ant Mill, an adversarial traffic pattern for RRGs when using routes of minimal length. Secondly, we demonstrate that the Ant Mill traffic pattern is also adversarial in other low-diameter direct interconnection networks such as Slimfly, Dragonfly, and Projective networks. Ant Mill is thoroughly motivated and evaluated, enabling future studies of low-diameter direct interconnection networks to leverage its findings.C. Camarero is under Ramón y Cajal contract RYC2021-033959-I from Spain’s Ministerio de Ciencia e Innovación with funding from the Mecanismo de Recuperación y Resiliencia de la Unión Europea. The three authors participate in these projects: PLANIFICADORES Y REDES PARA DATA CENTERS SOSTENIBLES project TED2021-131176B-I00 with funding from MCIN/AEI /10.13039/501100011033 and Unión Europea/NextGenerationEU/PRTR; REDES DE INTERCONEXIÓN, ACELERADORES HARDWARE Y OPTIMIZACIÓN DE APLICACIONES, project PID2019-105660RB-C22 with funding from MCIN/AEI /10.13039/501100011033; and ARQUITECTURA Y PROGRAMACIÓN DE COMPUTADORES ESCALABLES DE ALTO RENDIMIENTO Y BAJO CONSUMO III-UC (TEAMMATES UC) project PID2022-136454NB-C21 with funding from MICIU/AEI/10.13039/501100011033 and FEDER, UE. R. Beivide is supported by The Barcelona Supercomputing Center (BSC) under contract CONSER02023011NG

Polarized routing: an efficient and versatile algorithm for large direct networks

Supercomputer and datacenter networks can comprise hundreds of thousands of severs. Focusing on direct networks, different topologies have been proposed to attain such a high scalability, from Flattened Butter y and Dragon y to the most disruptive approach represented by Jellyfish, which is based on a random interconnection pattern. The routing problem on such networks remains a challenge that can be tackled as a topology aware solution, or with an agnostic approach. The case of random networks is a very special one because of the lack of an acceptable routing algorithm for them since no a priori topological clues can be exploited. In this paper, we introduce the Polarized Routing Algorithm, an adaptive non-minimal hop-by-hop mechanism for direct networks that can be used in a number of topologies, including Jellyfish. Polarized routing was conceived following two design criteria: a source-destination symmetry in the routes to enable load-balancing and to avoid undoing previously taken hops. A thorough experimentation shows Polarized routing constitutes an efficient and versatile solution, attaining the highest performance both in benign scenarios under uniform traffic patterns and in adverse ones on the tested networks. Interestingly, this algorithm provides important performance gains of more than 30% in the Jellyfish topology, for different traffic patterns, when compared to the state of the art solutions.This work has been supported by the Spanish Ministry of Science and Innovation under contracts PID2019-105660RBC22 and FJCI-2017-31643. Simulations were performed in the Altamira supercomputer at the University of Cantabria, a node of the Spanish Supercomputing Network

Lattice Graphs for High-Scale Interconnection Topologies

Torus networks of moderate degree have been widely used in the supercomputer industry. Tori are superb when used for executing applications that require near-neighbor communications. Nevertheless, they are not so good when dealing with global communications. Hence, typical 3D implementations have evolved to 5D networks, among other reasons, to reduce network distances. Most of these big systems are mixed-radix tori, which are not the best option for minimizing distances and efficiently using network resources. This paper is focused on improving the topological properties of this kind of networks. By using integral matrices to deal with Cayley graphs over Abelian groups, we have been able to propose and analyze a family of high-dimensional mesh-based interconnection networks. As they are built over n-dimensional grids that induce a regular tiling of space, these topologies have been denoted lattice graphs. Higher dimensional networks can be composed over these graphs by means of a lift operation, which is also introduced in the paper. Easy network partitioning and minimal routing algorithm are also provided for these topologies based on this new network operation. Later we focus on cubic crystal lattices for modeling symmetric 3D networks and to show how lattice graphs can help in the design of twisted interconnection networks. In all cases, the networks obtained are better, in topological terms, than their standard tori counterparts. Finally, some practical issues such as implementability and preliminary performance evaluations have been addressed at the end of this work.This work has been supported by the Spanish FPU grant AP2010-4900, the Spanish Science and Technology Commission (CICYT) under contracts TIN2010-21291-C02-02 and TIN2013-46957-C2-2-P, the European Union FP7 under Agreements ICT-288777 (Mont-Blanc) and ERC-321253 (RoMoL), the European HiPEAC Network of Excellence and the JSA no. 2013-119 as part of the IBM/BSC Technology Center for Supercomputing agreement

Throughput Unfairness in Dragonfly Networks under Realistic Traffic Patterns

Dragonfly networks have a two-level hierarchical arrangement of the network routers, and allow for a competitive cost-performance solution in large systems. Nonminimal adaptive routing is employed to fully exploit the path diversity and increase the performance under adversarial traffic patterns. Throughput unfairness prevents a balanced use of the resources across the network nodes and degrades severely the performance of any application running on an affected node. Previous works have demonstrated the presence of throughput unfairness in Dragonflies under certain adversarial traffic patterns, and proposed different alternatives to effectively combat such effect. In this paper we introduce a new traffic pattern denoted adversarial consecutive (ADVc), which portrays a real use case, and evaluate its impact on network performance and throughput fairness. This traffic pattern is the most adversarial in terms of network fairness. Our evaluations, both with or without transit-over-injection priority, show that global misrouting policies do not properly alleviate this problem. Therefore, explicit fairness mechanisms are required for these networks

Back Junction n-type Silicon Heterojunction Solar Cells with V2O5 Hole-selective Contact

AbstractIn this work, a back junction solar cell design is explored for n-type crystalline silicon by using thermally evaporated V2O5 as a rear hole contact and n+ amorphous silicon (a-Si:H) as a front electron contact. Photoconductance measurements revealed an implicit open-circuit voltage (i-VOC) of 670mV for the solar cell precursor (before metallization), achieved by maximizing the work function of V2O5 with a thin nickel capping layer. The VOC value of the finished device was lower than projected at 617mV, most likely due to poor passivation of the active area perimeter. Nonetheless, an efficiency of 14.2% was achieved (in polished substrates), proving the potential of such a novel structure