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This paper proposes a bipolar quasi-Z-source active neutral point clamped inverter (QZS-ANPCI) topology. It acts as a buck/boost inverter (3-phase, 3-level) to integrate renewable energy resources under their fluctuating DC voltages. We propose a symmetrical/unsymmetrical boost modulation control technique to mitigate the DC-link unbalance voltage problem in an ANPC inverter. This worthwhile control technique exploits voltage-current closedloops on AC and DC sides to regulate the desired parameters. Moreover, the constant boost control (CBC) modulation has provided a switching sequence that generates a symmetrical/unsymmetrical full shoot-through (FST) state for boosting input DC voltage in the proposed inverter. Detailed loss and efficiency analysis is carried out to show its superior performance under the proposed scheme. Furthermore, the total harmonic distortion (THD) of the proposed QZS-ANPCI meets IEEE Standard-519. Simulink/MATLAB (MathWorks, USA) and PSIM (Powersim, USA) software programs are used to simulate the proposed topology. To verify the theoretical proposals and simulation results, we have developed an experimental prototype setup (1 kW). Both simulation results and experimental data show satisfactory agreement and support the theoretical postulates. [ABSTRACT FROM AUTHOR]

Hybrid energy storage system (HESS) based on Li-ion and supercapacitor (SC) can play a potential role to stabilize the grid by providing the fast frequency ancillary services. The SC helps to reduce the battery charge/discharge stress and, hence, assists to extend the battery lifespan. The power sharing method (PSM) is the heart in control part to improve the HESS performance and reduce the battery stress. This paper proposes a hybrid PSM and investigates its impact on battery life extension along with its relation to the system design and regulation signal. The performance of hybrid PSM is compared with three other PSMs (low-pass filter, first and second rule based) in a 10 MW/10 MWh full-active parallel HESS for frequency regulation service in two networks: U.K. (national grid) and USA (PJM). Considering maximum possible battery lifetime upto 25 years, result shows that the hybrid PSM approach allows a degree of the better performance for both grid while the sharing of SC is kept maximum 2.0% and 2.5% (for U.S. and U.K. grid, respectively) of the HESS capacity. This study also analyses the impact of PSM on shared capacity and design of HESS for different grid regulation signals. [ABSTRACT FROM AUTHOR]

Understanding the controllability of complex networks continues to gain traction across disciplinary fields, including the exploration of infrastructure systems such as power grids. Through topological principles, this paper investigates the controllability features of an ensemble of 58 U.S. city-level power transmission networks in seven U.S. states. To perform structural controllability analyses, the topological characteristics of the ensemble of networks are first quantified, including degree, shortest path length, clustering coefficient, meshedness and betweenness centrality, as well as the uncertainty associated with these and related properties. Then, the paper focuses on the controllability features of complex networks so as to detect the minimal sets of driver nodes to possibly control the networks given system linearity assumptions. Accordingly, a node is critical, intermittent or redundant if it acts as a driver node in all, some, or none of the potentially controllable system configurations. Moreover, this paper constructs a new methodology to quantify the probability of being a driver node among the intermittent nodes, and reveals the controllability importance of system components. Results show that a small proportion of driver nodes can provide the conditions for controlling the slow dynamics of entire power transmission networks from a topological perspective, despite variations in network sizes and configurations. This paper also reveals that the driver nodes tend to avoid high degree nodes and high triangulation sub-graph nodes as well as high betweenness centrality nodes. The identification of topological differences for different categories of nodes (critical, intermittent or redundant) could help researchers and utilities understand the conditions for future functional controllability of power networks while improving their reliability and resilience as well as facilitating their transition into smart grid systems. [ABSTRACT FROM AUTHOR]

Microinverter-based photovoltaic (PV) systems now represent about 8% of the U.S. residential market, and offer many advantages including safety, performance, and simplified installation. The next-generation of PV microinverter will include more ancillary functions to support grid stability and reliability in more distributed generation smart-grid systems. A commercial ready PV microinverter not only focuses on efficiency and cost, but also on reliability, manufacturability, compliance of various grid-code, and electromagnetic interference regulations. This paper presents a detailed design and development process of a microinverter system from concept all the way to final commercial-ready prototype. Various design tradeoffs such as topology, control, filter solutions and power supplies, and mechanical packaging are provided. The required prototype testing and final system field tests are also presented. The presented design and test process intends to accelerate the future microinverter system design and development toward a commercial ready product. [ABSTRACT FROM PUBLISHER]

This paper focuses on three episodes of U.S. policymaking concerning illicit drugs, one during the Nixon administration, one during the Carter administration, and the contemporary war on drugs. Drawing upon evidence from drug-related Congressional hearings, the Gallup Poll, counts of relevant articles in the Readers' Guide to Periodical Literature and content analysis of the New York Times Index, the three episodes are characterized as fitting one of Cobb, Ross, and Ross's (1976) models of agenda-setting. The paper then considers the linkage between these differences in agenda setting and the very different policy content of each episode. While the Nixon and Carter episodes exemplify the dynamics of "mobilization" and "inside access" agenda setting respectively, the contemporary drug policy episode is anomalous. It suggests the need for an extension of the Cobb, Ross, and Ross typology to incorporate a new, "network" type of agenda setting. [ABSTRACT FROM AUTHOR]

This paper investigates community structure in the US Airport Network as it evolved from 1990 to 2010 by looking at six bi-monthly intervals in 1990, 2000 and 2010, using data obtained from the Bureau of Transportation Statistics of the US Department of Transport. The data contained monthly records of origin-destination pairs of domestic airports and the number of passengers carried. The topological properties and the volume of people traveling are both studied in detail, revealing high heterogeneity in space and time. A recently developed community structure detection method, accounting for the spatial nature of these networks, is applied and reveals a picture of the communities within. The patterns of communities plotted for each bi-monthly interval reveal some interesting seasonal variations of passenger flows and airport clusters that do not occupy a single US region. The long-term evolution of the network between those years is explored and found to have consistently improved its stability. The more recent structure of the network (2010) is compared with migration patterns among the four US macro-regions (West, Midwest, Northeast and South) in order to identify possible relationships and the results highlight a clear overlap between US domestic air travel and migration. [ABSTRACT FROM AUTHOR]

In this paper, we set out to analyse the evolving structure of the technological landscape on which our knowledge-based economies thrive. To this end, we develop a network-analytic model, which we use to characterise and study the evolving pattern of citations among all patents granted in the USA from 1975 to 1999. We find that (i) the structure of knowledge spillovers among technology domains features the distinguishing properties of a small world topology. However, (ii) during the 25 years observed there has been a consistent trend away from the small world topology, which (iii) is entirely explained by the disappearance of specialties encompassing multiple tightly interconnected technology domains. Our findings bear important strategic implications for both managers and policy makers. [ABSTRACT FROM AUTHOR]

Although recently there are extensive research on currency network using minimum spanning trees approach, the knowledge about the actual evolution of a currency web in Asia is still limited. In the paper, we study the structural evolution of an Asian network using daily exchange rate data. It was found that the correlation between Asian currencies and US Dollar, the previous regional key currency has become weaker and the intra-Asia interactions have increased. This becomes more salient after the exchange rate reform of China. Different from the previous studies, we further reveal that it is the trade volume, national wealth gap and countries growth cycle that has contributed to the evolutionary topology of the minimum spanning tree. These findings provide a valuable platform for theoretical modeling and further analysis. [ABSTRACT FROM AUTHOR]

Abstract: The National Institute of Standards and Technology (NIST) in collaboration with the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) has developed the Standard Reference Material (SRM) 2460 Bullets and 2461 Casings. NIST has also developed a 2D and 3D Topography Measurement and Correlation System for ballistics signature measurements. This system includes stylus instruments and a confocal microscope for 2D and 3D topography measurements, and a 2D and 3D topography correlation program developed by NIST. NIST and ATF are proposing to establish a National Ballistics Measurement Traceability and Quality System using these materials. In this paper, basic concepts and specific requirements for establishing ballistics measurement traceability are introduced; three key issues are discussed that include: (1) establishing a reference standard; (2) establishing an unbroken chain of calibrations; and (3) evaluating measurement uncertainty for both the geometrical topography measurements and the optical image correlations of the ballistics signatures. [Copyright &y& Elsevier]

In this paper we present a complete approach for the conflation of attributed vector digital mapping data such as the Vector Product Format (VPF) datasets produced and disseminated by the National Imagery and Mapping Agency (NIMA). While other work in the field of conflation has traditionally used statistical techniques based on proximity of features, the approach presented here utilizes all information associated with data, including attribute information such as feature codes from a standardized set, associated data quality information of varying levels, and topology, as well as more traditional measures of geometry and proximity. In particular, we address the issues associated with the problem of matching features and maintaining accuracy requirements. A hierarchical rule-based approach augmented with capabilities for reasoning under uncertainty is presented for feature matching as well as for the determination of attribute sets and values for the resulting merged features. Additionally, an in-depth analysis of horizontal accuracy considerations with respect to point features is given. An implementation of the attribute and geometrical matching phases within the scope of an expert system has proven the efficacy of the approach and is discussed within the context of the VPF data. [ABSTRACT FROM AUTHOR]