NSWC Philadelphia Division

(1892). IV. Disruption of the silver haloid molecule by mechanical force. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 34, No. 206, pp. 46-50.

Vertical power devices require significant attention to their edge termination designs to obtain higher breakdown voltages without substantial increase in ON-state resistance. A simple edge termination structure for a GaN p-n diode is proposed, comprising a full layer lightly doped p-type GaN region underneath the higher doped <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p} +\!+$ </tex-math></inline-formula> contact layer. A TCAD model of the device is developed, and removal of the portions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> ++ cap outside of the device active area in simulations is shown to increase the device blocking voltage capability. It causes the depletion width to increase in the lightly doped p-type layer and allows it to act similar to a junction termination extension (JTE). These predictions are validated empirically, resulting in a 52% measured increase in breakdown capability after selective removal of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> ++ cap. This simple edge termination technique can be formed with only a single low-energy nitrogen implant or etching procedure, greatly increasing its manufacturability over more complex structures. Design optimization studies are pursued in TCAD to determine optimal parameter values for further improving breakdown performance. It is shown that the proposed edge termination technique can be employed to produce future high voltage vertical GaN devices without a significant gain in ON-state resistance and with wide tolerance to process variations.

In some environments where prognostics and health management would be beneficial, for example on board U.S. naval vessels, installation location and accessibility to power system must be considered. In this study, we investigate condition based maintenance and fault diagnosis for hydraulic actuators in power constrained environments. The experimental setup for collecting data is outlined, and a data set replicating multiple types of faults is collected. Several types of machine learning classifiers, including random forest and classification trees, are tested on the data set. Prediction accuracy as well as training and testing times are compared, which are used as a surrogate for power consumption in this study. We find that the random forest algorithm provides the lowest error rate of the tested classifiers but has some of the highest training and testing times. Classification trees, on the other hand, provide a better tradeoff between accuracy and computation time.

In many applications, there are a number of data sources that can be collected and numerous features that can be calculated from these data sources. The error of big data has lead many to believe that the larger the data, the better the results. However, as the dimensionality of the data increases, the effects of the curse of dimensionality become more prevalent. Further, a large feature set also increases the computational costof data collection and feature calculation. In this study, we evaluated four dimensionality reduction techniques as part of a system for condition monitoring of a hydraulic actuator. Two feature selection techniques, ReliefF and variable importance, and two feature extraction techniques, principal component analysis and autoencoders, are used to reduce the input into three classification algorithms. We conclude that variable importance in conjunction with the random forest algorithm outperforms the other dimensionality reduction techniques. Feature selection has the added advantage of being able to remove data sources and features from the data collection and feature calculation process that are not present inthe relevant feature subset.

(1869). XLIV.—List of Coleoptera collected in Vancouver's Island by Henry and Joseph Matthews, with descriptions of some new species. Annals and Magazine of Natural History: Vol. 4, No. 24, pp. 369-385.

It is expected that the specialized weapons and sensory systems of future naval surface combatants will present much more challenging loads to the power systems in terms of increased magnitude and more dynamic characteristics. As such, it is anticipated that energy storage may play a significant role in accommodating these types of loads in future systems. The energy magazine (EM) concept has been proposed as one approach for incorporating these types of systems into future, as well as existing, platforms. The EM is envisioned as a power converter with inherent energy storage capability, providing buffering between connected loads and the shipboard power generation system. This paper presents results from power hardware-in-the-loop (PHIL) simulation experiments with a 200 MJ battery-based energy magazine supplying pulsating loads.

With the growing need to support large dynamic electric loads in microgrid environments, there has been a necessary push toward highly regulated dc distribution through power electronics. Unfortunately, these systems are nonlinear by nature and provide potentially destabilizing behavior at their source interfaces. To complicate matters further, many systems are built from independently designed subcomponents with little information shared between designs. It is, therefore, necessary to have stability-driven design requirements for each subsystem to enforce stable dynamics upon system integration. Traditional techniques are currently limited to either overly conservative large signal small-gain methods or small signal transfer function approaches that are unreliable for assuring large signal stability. This article proposes a generalized passivity-based stability criterion that conservatively estimates the domain of stability for an integrated nonlinear system. Through passivity partitioning and uniquely driven domain of passivity estimation techniques, this methodology provides interface conditions that certify stability while only requiring a reduced subset of knowledge of each connected subsystem <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</b>

The transition to the electric ship requires evolving from passive power regulation to active state anticipation with data linkage and controls between machinery and mission systems to become an agile power and energy system. Toward this, the Navy-sponsored research initiatives are currently developing a new power electronic power distribution system (PEPDS) paradigm. A key enabler for a successful PEPDS research and development (R and D) program is a well-developed and documented functional system architecture as the basis for collaborate research and subsequent future performance studies. The technical approach employs model-based systems engineering (MBSE) to capture stakeholder needs, behaviors, structures, and measures for PEPDS in a system model. This work has recently re-baselined the functional architecture, which is a solution-independent description of what a system does, defining the trade space for design. It has also explored a point solution for a PEPDS power train and Navy-Integrated Power and Energy Corridor (NiPEC) segment and investigated techniques for establishing connections between the System Model and external tools and models. This article provides an overview of the process, product, and prospects of that functional architecture, as well as the initial solution space exploration.

Advanced high-power shipboard applications such as electromagnetic rail-guns, semiconductor lasers, advanced radar, etc. create an emergent need to support large electric loads on various Navy vessels. With the necessary push towards highly regulated DC distribution through power electronics on shipboard power systems, these loads are becoming more likely to cause destabilizing behavior at their source interfaces. The stability of a system can be understood as the ability to operate as intended at a given operating point and if perturbed, the disturbance to the system will diminish over time and the system will return to its original operating behavior. Traditionally, it has been sufficient to analyze small signal stability through testing the ratio of the source impedance and load impedance with respect to the Nyquist Criterion. However, for Navy power systems with more complex circuit topologies and a trend towards higher switching frequencies, the impact of dual feed interfaces as well as previously unaccounted for common mode currents, could cause erroneous stability assessments when applying traditional techniques. This paper proposes a new method to classify the small signal stability of a complex DC interface. This is done through an expanded characterization of a system's impedances to address the coupling between all interface connections. In this study, an example power system is defined and classified using traditional techniques in comparison to the technique proposed.

Highly dynamic, high-power loads are anticipated to be introduced into existing and future surface combatants, aided by the simultaneous introduction of energy storage. As many of these loads may require dc power, it is expected that dc distribution systems may also be introduced to some extent. Deployment of these systems will also require suitable circuit protection to be employed, whether using circuit breakers or a breakerless approach leveraging the capabilities of the power electronic sources. This paper describes a 1 kV dc testbed incorporating many of these paradigms intended to examine and demonstrate concepts related to the design and protection of dc distribution systems for shipboard applications.

This study presents empirical validation of a simulated novel hybrid edge termination (HET) structure with planar ion implantation processing for vertical gallium nitride (GaN) diodes. The hybrid structure combines a junction termination extension (JTE) with superimposed guard rings (GRs), creating zones with alternating implantation depths. A design optimization strategy is employed to match the charge profile in the termination to that of a reference beveled edge termination, and is validated through the fabrication of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 1.5 kV GaN diodes. The breakdown voltage of the hybrid termination is tied to the fitting error between the charge profile of the hybrid structure and the reference bevel, as confirmed through simulations and experimental results. The proposed structure successfully emulates the properties of a bevel termination without the need for complex etching or lithography procedures. Additionally, the tolerance of the proposed hybrid structure to major process variations during the wafer growth and device fabrication are studied in simulations. The hybrid termination structure showcases remarkable robustness against major process variations, making it a viable choice for high-yield manufacturing. The findings and patterns presented in this work offer significant insights for the design and large-scale production of forthcoming high-power vertical GaN devices.

Abstract Cyber-physical systems (CPS) are finding increasing application in many domains. CPS are composed of sensors, actuators, a central decision-making unit, and a network connecting all of these components. The design of CPS involves the selection of these hardware and software components, and this design process could be limited by a cost constraint. This study assumes that the central decision-making unit is a binary classifier, and casts the design problem as a feature selection problem for the binary classifier where each feature has an associated cost. Receiver operating characteristic (ROC) curves are a useful tool for comparing and selecting binary classifiers; however, ROC curves only consider the misclassification cost of the classifier and ignore other costs such as the cost of the features. The authors previously proposed a method called ROC Convex Hull with Cost (ROCCHC) that is used to select ROC optimal classifiers when cost is a factor. ROCCHC extends the widely used ROC Convex Hull (ROCCH) method by combining it with the Pareto analysis for cost optimization. This paper proposes using the ROCCHC analysis as the evaluation function for feature selection search methods without requiring an exhaustive search over the feature space. This analysis is performed on 6 real-world data sets, including a diagnostic cyber-physical system for hydraulic actuators. The ROCCHC analysis is demonstrated using sequential forward and backward search. The results are compared with the ROCCH selection method and a popular Pareto selection method that uses classification accuracy and feature cost.

This brief presents a study on the effect of substrate choice on the performance of lateral GaN transistors. This is accomplished using a previously calibrated TCAD model of the device which was used to investigate the effect of substrate choice on capacitance-voltage characteristics of the device. It is shown in simulation that CGD and CDS have a demonstrable dependence on substrate selection and is consistent with expectations regarding the substrate materials conductivity. The device model was then used in transient simulation where the choice of substrate was shown to noticeably affect the model's turn-on and turn-off energy.

Medium Voltage Direct Current (MVDC) is an attractive power system option for commercial and naval ships. However, the lack of a comprehensive design strategy for MVDC circuit protection is a barrier to implementation. For a range of MVDC architectures, this paper explores the inter-relationships among the different functionalities that isolation devices can have, the technologies for implementing isolation devices, power quality requirements, protective relaying strategies, source design, load design, and energy storage. Because commercial products implementing the technologies do not currently exist for MVDC applications, their costs cannot be determined and therefore the optimal solution cannot yet be determined.

Past and present interest in six phase synchronous machines for shipboard use warrants development of a dynamic model, down to subtransient time scales, for use in larger, integrated electric power system simulations. Fundamental models of three phase synchronous machines are extended to include six phase machines.

Abstract Combined powertrain and velocity optimization can achieve significant energy efficiency improvements. However, due to the multitime scales in the system, the optimization is performed hierarchically and by separating time scales. To enforce state constraints, iteration between controller is introduced, for example, using Lagrange multipliers as metric for constraint violation. In this paper, an extension of the Koopman operator theory is presented with to obtain a data-driven approximation of the multipliers' behavior hence eliminating the need for iterations. Because the evolution of the Lagrange multipliers is the result of a fast dynamics optimization problem, and not the response of a nonlinear dynamical system, a novel technique in which the Lagrange multipliers are interpreted as a dynamic system is presented here. The approximate Koopman linear system is then derived using extended dynamic mode decomposition and it is integrated with the slow dynamic optimization. Results show that the Koopman augmented controller, which is solved as one single optimization, meets state and input constraints and achieves similar energy savings compared to an iterative approach.

A future naval capability program is currently underway to develop robust combat power and energy controls, along with methods and tools for evaluation of these controls. This paper presents progress in this effort, with the paper focusing more specifically on evaluation of tactical energy management controls. The approach for evaluation includes the development of a real-time electromagnetic transient simulation model of a representative naval shipboard power system, allowing evaluation of controls to span testing of controls purely in simulation, testing of deployed controls using controller hardware-in-the-loop simulation, and testing of controls interacting with physical hardware using power hardware-in-the-loop simulation. The approach also includes the use of offline simulation tools for screening scenarios of interest, the development of baseline control approaches for comparison, and the development of relevant metrics to assess the relative performance of control approaches. This paper presents an overview of the approach and current progress, as well as presenting results from interim analyses to illustrate the approach and initial lessons learned.

(1836). LXXVII. On the carboniferous series of the United States of North America. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 9, No. 56, pp. 407-411.

Analysis methods for DC power interfaces using techniques built around the Nyquist stability criteria have previously been utilized to create system level specifications to ensure the stability of interconnected systems. This paper extends these concepts to not just ensure stability, but to also ensure a guaranteed maximum level of voltage and current perturbation within the system. The technique relies on representation of the subsystems as two-port networks using a definition of two-port networks modified slightly from the conventional understanding. This paper discusses the modified two-port definition, how to combine these networks and use them to calculate ripple at an interface, and how these relationships can be used to form system specification. An example is also presented to illustrate how system specifications may be developed.

The Tierkreisgedichte of Elisabeth Langgasser are not well known. This is partly due to their obscurity, partly to their now unfashionable themes : nature and Christianity. Certainly academia's spotty treatment of the literature of the 1920s is partly responsible too. But it is precisely because the Tierkreisgedichte are so profoundly characteristic of this period that they deserve to be better known. What little secondary literature1 there is on Langgasser's verse is usually focused on the post-