Column generation approaches to ship scheduling with flexible cargo sizes

We present a Dantzig-Wolfe procedure for the ship scheduling problem with flexible cargo sizes. This problem is similar to the well-known pickup and delivery problem with time windows, but the cargo sizes are defined by an interval instead of a fixed value. We show that the introduction of flexible cargo sizes to the column generation framework is not straightforward, and we handle the flexible cargo sizes heuristically when solving the subproblems. This leads to convergence issues in the branch-and-price search tree, and the optimal solution cannot be guaranteed. Hence we have introduced a method that generates an upper bound on the optimal objective. We have compared our method with an a priori column generation approach, and our computational experiments on real world cases show that the Dantzig-Wolfe approach is faster than the a priori generation of columns, and we are able to deal with larger or more loosely constrained instances. By using the techniques introduced in this paper, a more extensive set of real world cases can be solved either to optimality or within a small deviation from optimalityTransportation; integer programming; dynamic programming

A View from the Field: A Practitioner\u27s Perspective on Teacher Education as a Site of Nonviolent Resistance – An Interview With Barbara Madeloni

In this audio piece, Dani O’Brien interviews the President of the Massachusetts Teacher’s Association (MTA), Barbara Madeloni. The MTA is the 110,000-member union representing educators in public PK-12 and higher education in Massachusetts. Barbara Madeloni is an education activist, a former high school English teacher, and a teacher-educator at the University of Massachusetts Amherst. She was elected President of the MTA in 2014, supported by a grassroots organization of teachers working to move the union in a more progressive, and activist, direction. In the interview, Barbara explains how the corporate assault on education produces structural violence, and talks about the nonviolent resistance she and other educators are engaged in. She discusses her campaign to become union president and the work she hopes to accomplish in that office

Class, Race, and the Discourse of “College for All.” A Response to “Schooling for Democracy”

We critique the “college for all” discourse by unveiling its relationship to the politics of education, the broader economic and political contexts, and the class and race structures embedded in society and schooling, including higher education. We analyze the current and future labor markets to demonstrate the ways that the “college for all” discourse overstates the need for math and science knowledge and skills within the workforce, and we analyze the debt burdens associated with college attendance and completion to demonstrate that the promised benefits of “college for all” are often illusory for low-income, racially, culturally, and linguistically diverse students. Thus, we argue that “college for all”—just like “no child left behind” and the “race to the top”—functions as an ideological velvet to soften education policy talk, talk that actually carries big sticks that punish the very students proclaimed to be the beneficiaries of the proposed changes in schooling. The results of schooling practices articulated by the “college for all” discourse are (a) the reinforcement of material barriers to the stated aims of educational access and equity, and (b) the fortification of the class and race status quo. We examine the ways that the transformation of schooling must be linked to the establishment of just social, economic, and political institutions, and to the formation of a citizenry prepared to engage in the struggles for these institutions

Holyoke Ethnic Studies Program Report: 2021-2022 School Year

Cariño. Community. Criticality. Culturally Relevant Content. Centering Students. How might schools in the U.S. be different if these five concepts were the guiding principles of teaching and learning? What transformations—what individual and societal shifts—might we experience if all members of our learning communities, particularly those from historically marginalized groups, were met with love, respect, support, an opportunity to understand the root causes of societal issues, and a chance to see themselves and their communities as irreplaceable parts of history? For students, teachers, and supporters of Holyoke Ethnic Studies (HES), these five concepts, also known as the 5 C’s, are not just aspirations, they are everyday realities waiting to be shared. In Holyoke, HES has experienced documented success in the form of student achievement, engagement, and matriculation. The heart of HES, however, is in the power of the people who advocate for humanizing education spaces with cariño, community, criticality, culturally relevant content, and students at the center. The purpose of this report is to offer a snapshot of the people, efforts, and legacies at the core of this important work. We begin with an explanation of Ethnic Studies, broadly answering the question: What is Ethnic Studies and why is it important? Next, we offer an overview of the HES program, paying special attention to the 5 C’s, the curriculum, community and university partnerships, and impact data on the program. We then situate HES among the legacies and lineages of other Ethnic Studies programs and activist movements throughout the U.S. in the following section, before sharing opportunities for solidarity and community engagement. We hope that this report can be a tool for educators, students, administrators, and community members to see themselves reflected in the broader fight for educational justice

A MILP model for quasi-periodic strategic train timetabling

In railways, the long-term strategic planning is the process of evaluating improvements to the railway network (e.g., upgrading a single track line to a double track line) and changes to the composition/frequency of train services (e.g., adding 1 train per hour along a certain route). The effects of different combinations of infrastructure upgrades and updated train services (also called scenarios), are usually evaluated by creating new feasible timetables followed by extensive simulation. Strategic Train Timetabling (STT) is indeed the task of producing new tentative timetables for these what-if scenarios. Unlike the more classic train timetabling, STT can often overlook (or at least give less importance to) some complementary aspects, such as crew and rolling stock scheduling. On the other hand, the different scenarios are likely to lead to very different timetables, hindering the common and effective practice of using existing timetables to warm start the solution process. We introduce the concept of quasi-periodic timetables, that are timetables where certain subsets of trains need to start at almost (rather than precisely) the same minute of every period. The additional flexibility offered by quasi-periodic timetables turned out to be crucial in real-life scenarios characterized by elevated train traffic. We describe a MILP based approach for strategic quasi-periodic train timetabling and we test it on 4 different realistic what-if scenarios for an important line in Norway. The timetables produced by our algorithm were ultimately used by the Norwegian Railway Directorate to select 3 out of the 4 scenarios for phasing the progressive expansion of the JȪren line.publishedVersio

Closing Information Gaps in Kakuma Refugee Camp: A Youth Participatory Action Research Study

This study explores the role of academic and social support on young people’s educational pursuits in Kenya’s Kakuma Refugee Camp. Pairing ethnographic methods with youth participatory action research, we find that support often manifests as abstract, decontextualized encouragement with little grounding in the educational opportunity structure. We argue that this motivational discourse generates information gaps, fueling aspirations that neither prepare youth for understanding, nor navigating the constraints they will encounter. In response, we designed a social media platform orienting Kakuma youth to the opportunity structure, while encouraging them to set realistic goals and plan accordingly. Designing a resource by, for, and with Kakuma youth, we illustrate that refugees have the rights and means to access information on which their everyday well‐being and futures depend. This study illustrates that critical understanding of local and global opportunities can empower, rather than demoralize, young people as they shape their futures in exile.HighlightsEducational support has limited value when decontextualized from opportunity structures.Critical understanding of opportunity constraints can empower, rather than demoralize, youth.Balancing hope and critical awareness is a central challenge in participatory action research, and in settings of forced displacement.Refugee youth advocate for their right to information on which their well‐being and futures depend.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147082/1/ajcp12277_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147082/2/ajcp12277.pd