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Innovations in the vapor deposition of metal coatings for target payloads in laser-based physics experiments under extreme conditions

Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics

Jankowski, Alan F.

The synthesis of metal foils with unique surface features such as waves and steps is of interest for use as payloads in targets for laser-driven physics experiments under dynamic loading conditions. Changes to the surface features are used to quantify the effects of the material strength during the deformation at high-strain rate high pressure. A traditional path to produce these target features is by precision machining processes using diamond tools. Limitations are encountered since many of the materials of interest and the size of the surface features are not often compatible with conventional machining-process methods. An alternative method to produce targets with unique surface features is through vapor synthesis. Two general approaches are taken - one is by replicating the features from the surface of a substrate mandrel, whereas the second is by using hard masks with timed exposure to the deposition vapor. In these approaches, postdeposition removal of a release layer yields a free-standing target with the desired surface features. Specific cases are presented for the physical vapor deposition of copper, aluminum, iron, vanadium, and tantalum to form targets with multiple layers, steps, and sinusoidal surface waves.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus

Lagrangian relaxation based heuristics for a chance-constrained optimization model of a hybrid solar-battery storage system

Optimization Online Repository

Singh, Bismark; Knueven, Bernard

Here, we develop a stochastic optimization model for scheduling a hybrid solar-battery storage system. Solar power in excess of the promise can be used to charge the battery, while power short of the promise is met by discharging the battery. We ensure reliable operations by using a joint chance constraint. Models with a few hundred scenarios are relatively tractable; for larger models, we demonstrate how a Lagrangian relaxation scheme provides improved results. To further accelerate the Lagrangian scheme, we embed the progressive hedging algorithm within the subgradient iterations of the Lagrangian relaxation. Lastly, we investigate several enhancements of the progressive hedging algorithm, and find bundling of scenarios results in the best bounds.

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TYPE Journal Article YEAR 2019
OSTI

Characterizing the roles of contributors in open-source scientific software projects

IEEE International Working Conference on Mining Software Repositories

Milewicz, Reed M.; Pinto, Gustavo; Rodeghero, Paige

The development of scientific software is, more than ever, critical to the practice of science, and this is accompanied by a trend towards more open and collaborative efforts. Unfortunately, there has been little investigation into who is driving the evolution of such scientific software or how the collaboration happens. In this paper, we address this problem. We present an extensive analysis of seven open-source scientific software projects in order to develop an empirically-informed model of the development process. This analysis was complemented by a survey of 72 scientific software developers. In the majority of the projects, we found senior research staff (e.g. professors) to be responsible for half or more of commits (an average commit share of 72%) and heavily involved in architectural concerns (seniors were more likely to interact with files related to the build system, project meta-data, and developer documentation). Juniors (e.g. graduate students) also contribute substantially - in one studied project, juniors made almost 100% of its commits. Still, graduate students had the longest contribution periods among juniors (with 1.72 years of commit activity compared to 0.98 years for postdocs and 4 months for undergraduates). Moreover, we also found that third-party contributors are scarce, contributing for just one day for the project. The results from this study aim to help scientists to better understand their own projects, communities, and the contributors' behavior, while paving the road for future software engineering research.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

Position paper: Towards usability as a first-class quality of HPC scientific software

Proceedings - 2019 IEEE/ACM 14th International Workshop on Software Engineering for Science, SE4Science 2019

Milewicz, Reed M.; Rodeghero, Paige

The modern HPC scientific software ecosystem is instrumental to the practice of science. However, software can only fulfill that role if it is readily usable. In this position paper, we discuss usability in the context of scientific software development, how usability engineering can be incorporated into current practice, and how software engineering research can help satisfy that objective.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus
Results 23801–23900 of 99,299
Results 23801–23900 of 99,299