On-line bin packing with restricted repacking

Semi-on-line algorithms for the bin-packing problem allow, in contrast to pure on-line algorithms, the use of certain types of additional operations for each step. Examples include repacking, reordering or lookahead before packing the items. Here we define and analyze a semi-on-line algorithm where for each step at most k items can be repacked, for some positive integer k. We prove that the upper bound for the asymptotic competitive ratio of the algorithm is a decreasing function of k, which tends to 3/2 as k goes to infinity. We also establish lower bounds for this ratio and show that the gap between upper and lower bounds is relatively small.     

Social network analysis and the evaluation of leadership networks

Leadership development practitioners are increasingly interested in social networks as a way to strengthen relationships among leaders in fields, communities, and organizations. This paper offers a framework for conceptualizing different types of leadership networks and uses case examples to identify outcomes typically associated with each type of network. Evaluating leadership networks is a challenge for the field of leadership development. Social network analysis (SNA) is an evaluation approach that uses mathematics and visualization to represent the structure of relationships between people, organizations, goals, interests, and other entities within a larger system. In this article we describe core social network concepts and the application of them to illuminate the value of SNA as an evaluation tool.     

A Branch and Cut solver for the maximum stable set problem

This paper deals with the cutting-plane approach to the maximum stable set problem. We provide theoretical results regarding the facet-defining property of inequalities obtained by a known project-and-lift-style separation method called edge-projection, and its variants. An implementation of a Branch and Cut algorithm is described, which uses edge-projection and two other separation tools which have been discussed for other problems: local cuts (pioneered by Applegate, Bixby, Chvátal and Cook) and mod-k cuts. We compare the performance of this approach to another one by Rossi and Smiriglio (Oper. Res. Lett. 28:63–74, 2001) and discuss the value of the tools we have tested.     

Impacts of urbanization on palustrine (depressional freshwater) wetlands—research and management in the Puget Sound region

This paper summarizes the results of the Puget Sound Wetlands and Stormwater Management Research Program, which examined the impacts of urban stormwater on wetlands. Results are presented for data collected between 1988 and 1995 for 19 wetlands, showing changes in wetland hydrology resulting from urban conversion and the subsequent impacts on plant and amphibian communities. The amount of watershed imperviousness, the forested area, and the degree of outlet constriction were found to be the most significant factors affecting wetland hydroperiods. As hydroperiods changed, plant communities shifted towards communities adaptable to the new hydrograph. Wetlands with water level fluctuation above 20 cm resulted in lower plant richness in the emergent and scrub-shrub zones. Similarly, wetlands with water level fluctuation greater than 20 cm were significantly more likely to have low amphibian richness of three or fewer species. A primary goal of the research program was to employ the results to improve the management of both wetlands and stormwater in urban areas. Hydrologic guidelines were applied to King County's basin planning and master drainage planning efforts. Controls that focused on minimizing impervious surfaces and maximizing forest retention in the wetland watershed proved to be the most widely usable strategy.     

Minimizing the maximum travel time in a combined model of facility location and network design

This paper presents a combined Facility Location/Network Design Problem which simultaneously considers the location of facilities and the design of its underlying network so as to minimize the maximum customer-facility travel time. The model generalizes the classical p-center problem and has various applications in regional planning, distribution, telecommunications, emergency systems, and other areas. Two mixed integer programming formulations are presented and compared. Several valid inequalities are derived for the most promising of these formulations to strengthen its LP relaxation bound and to reduce the enumeration tree. Numerical results of a series of computational experiments for instances with up to 100 nodes and 500 candidate links are reported.     

Optimal triangulation of large real world input-output matrices

In this paper we present optimum triangulations of a large number of input-output matrices. In particular, we report about a series of (44,44)-matrices of the years 1959, 1965, 1970, 1975 of the countries of the European Community, about all (56, 56)-matrices compiled by Deutsches Institut für Wirtschaftsforschung for the Federal Republic of Germany, and about the (60,60)-matrices of the Statistisches Bundesamt of the Federal Republic of Germany. These optimum triangulation were obtained with a code developed by the authors which utilizes new polyhedral results for the triangulation problem in a linear programming cutting plane framework. With this code the range of solvability of triangulation problems was more than doubled (in terms of sector numbers) compared to previous work. In particular, for none of the triangulation problems mentioned above optimum solutions were known before. Moreover, we discuss various claims about properties of optimum solutions made in the literature and question some common concepts of analysing triangulated input-output matrices.

     

Infant regulation during the pandemic: Associations with maternal response to the COVID-19 pandemic,well-being,and socio-emotional investment

In the transition to parenthood, the COVID-19 pandemic poses an additional strain on parental well-being. Confirmed infections or having to quarantine, as well as public health measures negatively affect parents and infants. Contrary to previous studies mainly focusing on the well-being of school-aged children and their parents during lockdown periods, the present study investigated how mothers of infants respond to the COVID-19 pandemic and whether this is related to maternal well-being, maternal socio-emotional investment, and infant regulation. Between April and June 2021, 206 mothers of infants (M_age = 7.14 months, SD_age = 3.75 months) reported on COVID-19 infections, their response to the COVID-19 pandemic, their well-being, socio-emotional investment, and their infant’s regulation. Exploratory factor analyses yielded five dimensions of maternal response to the COVID-19 pandemic: social distancing, worrying about the child, birth anxiety, distancing from the child, and information on COVID-19-related parenting behavior and support. These dimensions were related to mother-reported infant regulatory problems. Path analyses revealed paths via reduced maternal well-being and maternal socio-emotional investment. Maternal perceptions of infant regulatory problems are related to how the mothers respond to the COVID-19 pandemic. Better information about COVID-19-related parenting behavior and support might buffer against these effects.