Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Sonar & Radar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Use of space-filling curves for additive manufacturing of three dimensionally varying graded dielectric structures using fused deposition modeling

Abstract: In this paper the authors present a novel design tool for realizing dielectric structures with spatially varying electromagnetic properties via additive manufacturing (AM). To create tool paths ideal for AM processes, space-filling curves were utilized. Using fused deposition modeling (FDM), spatially varying structures were printed that produced a spatially varying relative permittivity. A wide range of varying fill fractions were printed and evaluated, demonstrating good agreement between the simulated and measured results. Furthermore, the authors verified that this design tool can be applied to practical structures by designing, printing and testing a gradient index flat lens.

Laser Transferable Polymer-Ionic Liquid Separator/Electrolytes for Solid-State Rechargeable Lithium-Ion Microbatteries

Abstract: A laser-transferable polymer gel separator formulated from an imidazolium-based ionic liquid, poly(vinylidene fluoride) (PVDF)-HFP, and ceramic nanoparticles was prepared and electrochemically characterized by ac-impedance spectroscopy and in lithium-ion microbatteries. Size and weight percent effects of the nanoparticulates added to the laser-transferred separator indicate that nanoparticulates under 100 nm in size and in the 10 wt % range exhibited the highest ionic conductivity (1-3 mS/cm). Li-ion microbatteries prepared using this separator, a LiCoO 2 cathode, and a carbon anode maintained an average discharge voltage of up to 4.2 V with a reversible specific energy of 330 mWh/g.

Amorphous Al 90 Fe x Ce 10 − x alloys: X-ray absorption analysis of the Al, Fe and Ce local atomic and electronic structures

Abstract: X-ray-absorption fine structure (XAFS) above the Fe K edge, the Ce ${L}_{3}$ edge, and the Al K edge in amorphous ${\mathrm{Al}}_{90}{\mathrm{Fe}}_{x}{\mathrm{Ce}}_{10\ensuremath{-}x}$ $(x=3,$ 5, and 7) alloys have been measured and analyzed. Quantitative analyses of the Fe K-edge and Ce ${L}_{3}$-edge extended XAFS spectra are limited to local structure parameters of the first coordination sphere. Comparison of experimental x-ray-absorption near-edge structure (XANES) spectra with theoretical multiple-scattering (MS) XANES spectra for model compounds, such as crystalline ${\mathrm{FeAl}}_{6}$ and ${\mathrm{CeAl}}_{4},$ allows one to determine the local structure around the aluminum, iron, and Ce sites in ternary amorphous alloys. Using the theoretical MS approach, we show that the Fe and Al K-edge XANES are sensitive to the structure of coordination spheres, which extend up to nearly 4.4 and 3.3 \AA{}, respectively. The Ce ${L}_{3}$-edge XANES, on the other hand, is sensitive to the structure that extends up to 3.15 \AA{}.

Influence of bore and rail geometry on an electromagnetic naval railgun system

Abstract: A large-scale railgun is being considered by the U.S. navy as a future long range (>200 nm) naval weapon system. The notional concept includes a 15 kg projectile with a 2.5 km/sec muzzle velocity. The choice of bore and rail geometry for such a weapon can influence key aspects of the total system design. This study explored a range of bore and rail geometries and looked at their effects on key railgun system parameters such as parasitic mass, inductance gradient, linear current density, required pulse forming network (PFN) size, and barrel mass. Preliminary solid modeling and structural analysis of the integrated launch package was performed in order to quantify parasitic mass. Inductance gradient calculations were based on a current density distribution analysis. A PFN/Launcher numerical simulation model was then used to determine linear current density and PFN size. Finally, barrel mass was estimated by structural analysis based on calculated rail repulsive forces. Trends and sensitivities of the different parameters to changes in the bore and rail geometries are presented and conclusions are given.