A survey of statistical network models

Networks are ubiquitous in science and have become a focal point for discussion in everyday life. Formal statistical models for the analysis of network data have emerged as a major topic of interest in diverse areas of study, and most of these involve a form of graphical representation. Probability models on graphs date back to 1959. Along with empirical studies in social psychology and sociology from the 1960s, these early works generated an active network community and a substantial literature in the 1970s. This effort moved into the statistical literature in the late 1970s and 1980s, and the past decade has seen a burgeoning network literature in statistical physics and computer science. The growth of the World Wide Web and the emergence of online networking communities such as Facebook, MySpace, and LinkedIn, and a host of more specialized professional network communities has intensified interest in the study of networks and network data. Our goal in this review is to provide the reader with an entry point to this burgeoning literature. We begin with an overview of the historical development of statistical network modeling and then we introduce a number of examples that have been studied in the network literature. Our subsequent discussion focuses on a number of prominent static and dynamic network models and their interconnections. We emphasize formal model descriptions, and pay special attention to the interpretation of parameters and their estimation. We end with a description of some open problems and challenges for machine learning and statistics.Comment: 96 pages, 14 figures, 333 reference

Reversible sodiation of electrochemically deposited binder- and conducting additive-free Si-O-C composite layers

Binder- and conducting additive-free Si-O-C composite layers are deposited electrochemically under potentiostatic conditions from sulfolane-based organic electrolyte. Quartz crystal microbalance with damping monitoring is used for evaluation of the layer growth and its physical properties. The sodiation-desodiation performance of the material is afterward explored in Na-ion electrolyte. In terms of specific capacity, rate capability, and long-term electrochemical stability, the experiments confirm the advantages of applying the electrochemically formed Si-O-C structure as anode for Na-ion batteries. The material displays high (722 mAh g^-1) initial reversible capacity at j = 70 mA g^-1 and preserves stable long-term capacity of 540 mAh g^-1 for at least 400 galvanostatic cycles, measured at j = 150 mA g^-1. The observed high performance can be attributed to its improved mechanical stability and accelerated Na-ion transport in the porous anode structure. The origin of the material electroactivity is revealed based on X-Ray photoelectron spectroscopic analysis of pristine (as deposited), sodiated, and desodiated Si-O-C layers. The evaluation of the spectroscopic data indicates reversible activity of the material due to the complex contribution of carbon and silicon redox centers

Electrical Capacitance Tomography to Measure Moisture Distribution of Polymer Foam in a Microwave Drying Process

Moisture distribution information is a critical element in drying processes. The drying of products by employing high-power microwave (MW) technology is widely used in the industry. Although microwaves allow volumetric and selective heating resulting in a significant reduction of processing time and energy consumption, there is always a risk of non-uniform moisture distribution in the final product. This paper investigates the capability of a designed electrical capacitance tomography (ECT) sensor to estimate the moisture distribution of polymer foams in a microwave drying process. The moisture distribution is estimated based on the non-intrusive contactless measurements of the electrical capacitances between the electrodes mounted on a frame around the target polymer foam. The obtained moisture information can be employed as feedback to a controller to adjust the power level of each microwave source in the microwave system to reduce or eliminate the non-homogeneity of the moisture distribution inside the polymer foam. In a series of experiments, we first examine the capability of the ECT sensor in estimating the moisture distribution in a stationary foam. We extend the tests to estimating the moisture distribution in a case where the foam is moving on a conveyor belt. Several study variables are taken, including the sample size, the sample location, the moisture percentage, the conveyor belt speed, and the microwave power. These experiments show that the sensor has a satisfactory accuracy in estimating the moisture distribution of the foam, and the ECT measurements can be further used in a closed-loop control system

Sepsis Diagnostics: Intensive Care Scoring Systems Superior to MicroRNA Biomarker Testing

Sepsis represents a serious medical problem accounting for numerous deaths of critically ill patients in intensive care units (ICUs). An early, sensitive, and specific diagnosis is considered a key element for improving the outcome of sepsis patients. In addition to classical laboratory markers, ICU scoring systems and serum miRNAs are discussed as potential sepsis biomarkers. In the present prospective observational study, the suitability of miRNAs in sepsis diagnosis was tested based on proper validated and normalized data (i.e., absolute quantification by means of Droplet Digital PCR (ddPCR)) in direct comparison to classical sepsis markers and ICU scores within the same patient cohort. Therefore, blood samples of septic intensive care patients (n = 12) taken at day of admission at ICU were compared to non-septic intensive care patients (n = 12) and a healthy control group (n = 12). Our analysis indicates that all tested biomarkers have only a moderate informative power and do not allow an unequivocal differentiation between septic and non-septic ICU patients. In conclusion, there is no standalone laboratory parameter that enables a reliable diagnosis of sepsis. miRNAs are not superior to classical parameters in this respect. It seems recommendable to measure multiple parameters and scores and to interpret them with regard to the clinical presentation

System identification of conveyor belt microwave drying process of polymer foams using electrical capacitance tomography

The microwave drying process has a wide application in industry, including drying polymer foams after the impregnation process for sealings in the construction industry. The objective of the drying process is to reach a certain moisture in the foam by adjusting the power levels of the microwave sources. A moisture controller can be designed to achieve this goal; however, a process model is required to design model-based controllers. Since complex physics governs the microwave drying process, system identification tools are employed in this paper to exploit the process input and output information and find a simplified yet accurate model of the process. The moisture content of the foam that is the process output is measured using a designed electrical capacitance tomography (ECT) sensor. The ECT sensor estimates the 2D permittivity distribution of moving foams, which correlates with the foam moisture. Experiments are conducted to collect the ECT measurements while giving different inputs to the microwave sources. A state-space model is estimated using one of the collected datasets and is validated using the other datasets. The comparison between the model response and the actual measurements shows that the model is accurate enough to design a controller for the microwave drying process

Tomography-assisted control for the microwave drying process of polymer foams

This paper presents the integration of electrical capacitance tomography (ECT) with a moisture controller for the microwave drying of polymer foam. The proportional–integral (PI) control and the linear quadratic Gaussian (LQG) control are employed in designing the controller. The control objective in this process is that the moisture of polymer foam after the drying process reaches the desired set point. The permittivity distribution of polymer foam after the drying process is estimated in real-time using a designed ECT sensor and transferred as feedback to the controller. Since the permittivity and the moisture are strongly correlated, the material moisture can be controlled by controlling the permittivity. A state-space model is derived for the microwave drying process based on a system identification approach using the experimental data from the process. The derived model is employed in designing the LQG controller and adjusting the parameters of the PI controller. The designed controllers are implemented on a testbed microwave oven, and the experimental results show that the designed controllers are able to follow the desired set point moisture. The performance of the system with both controllers is compared, and their advantages and disadvantages are discussed. Moreover, the benefits of having a moisture controller for the microwave drying process are shown in simulation studies compared to an uncontrolled system

Typen des interpersonalen und medialen Kommunikations- und Informationshandelns während der Corona-Pandemie

Die Corona-Pandemie stellt eine Phase der Unsicherheit dar und geht mit Handlungs- und Entscheidungsbedarfen einher, für deren Bewältigung das individuelle Kommunikations- und Informationshandeln eine wichtige Rolle spielt. Dabei ziehen Rezipient*innen situationsbedingt bestimmte Quellen anderen vor und legen beispielsweise unter bestimmten Bedingungen mehr Wert auf interpersonalen Austausch anstelle von medialer Suche. Das Ziel des vorliegenden Beitrags liegt darin, verschiedene Typen des interpersonalen und medialen Kommunikations- und Informationshandelns mit Bezug zur Corona-Pandemie zu identifizieren und ihre Spezifika herauszuarbeiten. Auf Basis 21 leitfadengestützter Interviews, die mittels einer qualitativen Inhaltsanalyse ausgewertet wurden, konnten je sechs inhaltsbezogene und zwei strategiebezogene Typen des interpersonalen sowie des medialen Kommunikations- und Informationshandelns identifiziert werden. Bei den interpersonalen Typen liegt der Fokus auf Emotionsbewältigung, auf Erfahrungs- oder Informationsaustausch. Sie zeichnen sich durch unterschiedliche Offenheit gegenüber dem Thema aus, während die medialen Typen von konkreten Interessensfeldern und sowohl durch Strategien der aktiven, gezielten Suche als auch der passiven Form des Scanning gekennzeichnet sind. Mit Blick auf die vorliegenden Erkenntnisse zeigt sich für die frühe Phase der Pandemie ein hohes Informationsbedürfnis und eine umfassende, auch selektive und kritische Rezeption medialer Inhalte und eine durch emotionale und informationelle Unterstützung geprägte Art des persönlichen Austauschs im sozialen Umfeld.The corona pandemic is a phase of uncertainty that is accompanied by the need for action and decision-making. To cope with uncertainties and prepare for decision-making interpersonal communication and information-seeking behavior play an important role. Depending on situational factors, individuals prefer certain sources to others and, for example, place more weight on interpersonal exchange instead of seeking information using media channels. This paper aims to identify different types of interpersonal communication and media information seeking about the Corona pandemic. Based on 21 semi-structured interviews, which were analyzed by qualitative content analysis, six content-related and two strategy-related types of interpersonal communication and information-seeking behavior using media channels were identified. The focus of the identified types of interpersonal communication was on coping with emotions and on exchanging experiences or information as types of social support and was further characterized by different degrees of openness to the topic. In contrast, the types of information-seeking behaviors using media channels were characterized by concrete fields of interest and by strategies of both active, targeted seeking, and passive forms of scanning. The findings illustrate that the early phase of the pandemic revealed a high need for information and a comprehensive, also selective, and critical reception of media content, whereas interpersonal communication was characterized by emotional and informational support

"Selbst schuld!" - Stigmatisierung von COVID-19-Erkrankten und der Einfluss des individuellen Informationshandelns

Vom neuartigen Coronavirus betroffene Menschen berichten von Beschimpfungen auf offener Straße, Hassmails und Nachbar*innen, die auf Distanz gehen. Sowohl die Angst vor dem Ungewissen als auch vor Ansteckung und der damit verbundenen Mortalität, führen dazu, dass Betroffene von Infektionskrankheiten wie COVID-19 vorverurteilt, ausgegrenzt, diskriminiert und somit stigmatisiert werden. Dieser Beitrag geht der Frage nach, wie stark die Stigmatisierung von COVID-19-Erkrankten in Deutschland ausgeprägt ist und welche Faktoren die Stigmatisierung beeinflussen. Hierzu wurden im April 2020 997 Menschen in Niedersachsen mittels eines Online-Panels befragt. Die Ergebnisse zeigen, dass die Stigmatisierung insgesamt eher gering ausgeprägt ist. Im Vergleich der Stigma-Komponenten fällt die Tendenz zu diskriminierendem Verhalten am stärksten aus. Zudem zeigte sich, dass Männer im Vergleich zu Frauen sowie Personen mit höherer Risikowahrnehmung zu einer stärker stigmatisierenden Haltung tendieren. Unter den kommunikationsbezogenen Einflussfaktoren zeigte sich, dass die Nutzung softer und sozial eingebetteter Nachrichtenquellen, wie Boulevardzeitungen oder Influencer*innen, mit einer stärkeren Stigmatisierung, die Nutzung traditioneller Nachrichtenquellen, wie dem öffentlich-rechtlichen Rundfunk, hingegen mit einer geringeren Stigmatisierung von Corona-Betroffenen einhergeht.People affected by the novel coronavirus report verbal insults on the street, hate mail, and neighbors who keep their distance. Fear of the unknown, as well as fear of infection and the mortality associated with the disease, lead to people affected by COVID-19 being prejudged, excluded, discriminated against, and thus stigmatized. This paper explores the extent of stigmatization of COVID-19 patients at the beginning of the pandemic in Germany and the factors that affect stigmatization. For this purpose, 997 people in Lower Saxony, Germany, were surveyed by means of an online panel in April 2020. The results show that stigmatization is overall rather low, and of all stigma components, the tendency to discriminatory behavior was the highest. In addition, male gender and stronger risk perception were positively related to stigmatizing attitudes. Among the communication-related influencing factors, the use of soft and socially embedded news sources, such as yellow press or blogs, was found to be associated with a stronger stigmatizing attitude toward corona patients. The use of traditional news sources, such as public service media, was, however, associated with a lower stigmatizing attitude