Selecting the rank of truncated SVD by Maximum Approximation Capacity

Truncated Singular Value Decomposition (SVD) calculates the closest rank-$k$ approximation of a given input matrix. Selecting the appropriate rank $k$ defines a critical model order choice in most applications of SVD. To obtain a principled cut-off criterion for the spectrum, we convert the underlying optimization problem into a noisy channel coding problem. The optimal approximation capacity of this channel controls the appropriate strength of regularization to suppress noise. In simulation experiments, this information theoretic method to determine the optimal rank competes with state-of-the art model selection techniques.Comment: 7 pages, 5 figures; Will be presented at the IEEE International Symposium on Information Theory (ISIT) 2011. The conference version has only 5 pages. This version has an extended appendi

Data-driven modeling of collaboration networks: A cross-domain analysis

We analyze large-scale data sets about collaborations from two different domains: economics, specifically 22.000 R&D alliances between 14.500 firms, and science, specifically 300.000 co-authorship relations between 95.000 scientists. Considering the different domains of the data sets, we address two questions: (a) to what extent do the collaboration networks reconstructed from the data share common structural features, and (b) can their structure be reproduced by the same agent-based model. In our data-driven modeling approach we use aggregated network data to calibrate the probabilities at which agents establish collaborations with either newcomers or established agents. The model is then validated by its ability to reproduce network features not used for calibration, including distributions of degrees, path lengths, local clustering coefficients and sizes of disconnected components. Emphasis is put on comparing domains, but also sub-domains (economic sectors, scientific specializations). Interpreting the link probabilities as strategies for link formation, we find that in R&D collaborations newcomers prefer links with established agents, while in co-authorship relations newcomers prefer links with other newcomers. Our results shed new light on the long-standing question about the role of endogenous and exogenous factors (i.e., different information available to the initiator of a collaboration) in network formation.Comment: 25 pages, 13 figures, 4 table

Modeling the formation of R\&D alliances: An agent-based model with empirical validation

We develop an agent-based model to reproduce the size distribution of R\&D alliances of firms. Agents are uniformly selected to initiate an alliance and to invite collaboration partners. These decide about acceptance based on an individual threshold that is compared with the utility expected from joining the current alliance. The benefit of alliances results from the fitness of the agents involved. Fitness is obtained from an empirical distribution of agent's activities. The cost of an alliance reflects its coordination effort. Two free parameters $a_{c}$ and $a_{l}$ scale the costs and the individual threshold. If initiators receive $R$ rejections of invitations, the alliance formation stops and another initiator is selected. The three free parameters $(a_{c},a_{l},R)$ are calibrated against a large scale data set of about 15,000 firms engaging in about 15,000 R\&D alliances over 26 years. For the validation of the model we compare the empirical size distribution with the theoretical one, using confidence bands, to find a very good agreement. As an asset of our agent-based model, we provide an analytical solution that allows to reduce the simulation effort considerably. The analytical solution applies to general forms of the utility of alliances. Hence, the model can be extended to other cases of alliance formation. While no information about the initiators of an alliance is available, our results indicate that mostly firms with high fitness are able to attract newcomers and to establish larger alliances

Present day Nd isotopic composition of seawater and sediment leaches from the Pacific sector of the Southern Ocean

ABSTRACT FINAL ID: PP11B-1785 The Southern Ocean plays a key role in the climate evolution of Earth’s history, nevertheless its biggest region, the Pacific sector, has been poorly investigated in comparison to other regions in many paleoceanographic aspects. Some of them will try to be explained by the SOPATRA Project (SOuth PAcific TRAnsects). One of those aspects is radiogenic isotope compositions. Hereby we present the first εNd data extracted from Fe-Mn hydroxide coatings of bulk sediments from the Pacific sector of the Southern Ocean. These surface sediments results, scattered along a longitudinal transect of about 10,000 miles, collected from cruise SO213 from middle Chile to New Zealand (between 36°S and 45°S), represent a reliable overview of the present day Nd isotopic composition of the ambient water masses in this region, and will provide useful information for the interpretation of later downcore studies of this water mass tracer. Multiple analysis were carried out to confirm the reliability of the data as well as the validity of the applied leaching method: 1) Measurements of the present day radiogenic Nd bottom water signatures were compared to the Nd isotope compositions of the leachates in order to verify their seawater origin. 2) The leachates’ 87Sr/86Sr isotope ratios were monitored to confirm the holocenic origin of the samples. 3) Radiogenic Nd and Sr compositions of the detrital fraction of the sediment were measured after total dissolution of the same set of samples in order to exclude detrital contamination of leachates. 4) Two different leaching procedures were tested. Preliminary results show εNd values between -4 and -6, corresponding the lowest values to central south Pacific, which could represent the imprint of the circumpolar deep water moving northward. These findings are in agreement with other authors who extracted bottom water Nd isotope compositions from manganese nodules

How change agents and social capital influence the adoption of innovations among small farmers: Evidence from social networks in rural Bolivia

"This paper presents results from a study that identified patterns of social interaction among small farmers in three agricultural subsectors in Bolivia—fish culture, peanut production, and quinoa production—and analyzed how social interaction influences farmers' behavior toward the adoption of pro-poor innovations. Twelve microregions were identified, four in each subsector, setting the terrain for an analysis of parts of social networks that deal with the diffusion of specific sets of innovations. Three hundred sixty farmers involved in theses networks as well as 60 change agents and other actors promoting directly or indirectly the diffusion of innovations were interviewed about the interactions they maintain with other agents in the network and the sociodemographic characteristics that influence their adoption behavior. The information derived from this data collection was used to test a wide range of hypotheses on the impact that the embeddedness of farmers in social networks has on the intensity with which they adopt innovations. Evidence provided by the study suggests that persuasion, social influence, and competition are significant influences in the decisions of farmers in poor rural regions in Bolivia to adopt innovations. The results of this study are meant to attract the attention of policymakers and practitioners who are interested in the design and implementation of projects and programs fostering agricultural innovation and who may want to take into account the effects of social interaction and social capital. Meanwhile, scholars of the diffusion of innovations may find evidence to further embrace the complexity and interdependence of social interactions in their models and approaches." from Author's AbstractSocial networks, Agricultural innovation, Change agent, Social capital,

Who has influence in multistakeholder governance systems?

As multistakeholder governance has emerged as an important feature in development, new governance structures that foster the participation of multiple stakeholders from the public sector, civil society, and the private sector have emerged in various fields, ranging from the management of natural resources to the provision of public services. To make such governance structures work, it is essential to understand how different stakeholders influence decisionmaking and what determines their influence. This paper uses Net-Map, an innovative participatory method, to analyze how networking influences decisionmaking in multistakeholder governance structures, using the case of the governance board of the White Volta River Basin in northern Ghana as an example. The method visualizes both the relations between all stakeholders in watershed management as perceived by the 17 members on the board and their influence on development outcomes. The study suggests that significant effects of social networking are at play beyond the formal lines of command and funding as stakeholders in watershed management make decisions. Stakeholders are more influential if they participate more prominently in information exchange and provide more advice to others. This counterbalances the overrepresentation of government actors on the board. Meanwhile some government organizations have a low level of influence, even though they are central in giving funding and command. These findings may be interesting for program leaders and policymakers in watershed management: when designing governance structures they need to take into account the importance of social networking to attain main objectives of watershed development; it is important to provide space that allows the exchange of information and advice among stakeholders. Meanwhile, policymakers and program leaders as well must consider overrepresentation of social network champions in multistakeholder governance structures and the limited capacity of government bodies in social networking. The paper serves to introduce not only the specific findings concerning this case study but also the participatory research method (Net-Map) that was used.decisionmaking, multistakeholder governance, Natural resource management, Social networks,

The Determinants of Environmental Innovations and Patenting: Germany Reconsidered

This paper provides new evidence on the objectives and determinants of different typesof innovations and patents, environmental as opposed to other innovations and patents,and different variants of environmental innovations and patents. We investigate howfirm-specific and sector-specific driving forces differ by innovation type. Moreover, weoutline the functions that different innovation types have for environmental and innovationpolicies. We find that eco-innovators put relatively more attention to cost reduction, inparticular the reduction of energy and resource costs, compared to other innovators.Cost pressure and reliable, predictable and strict framework conditions of environmentalpolicy turns out to be an important driver for more incremental, firm-level eco-innovationscontributing to the diffusion of principally known technologies among firms. By contrast,more far-reaching patented eco-innovations are driven by the opportunity to create newmarkets and by government subsidies.Environmental innovation, patent, discrete choice models