Orientational Melting in Carbon Nanotube Ropes

Using Monte Carlo simulations, we investigate the possibility of an orientational melting transition within a "rope" of (10,10) carbon nanotubes. When twisting nanotubes bundle up during the synthesis, orientational dislocations or twistons arise from the competition between the anisotropic inter-tube interactions, which tend to align neighboring tubes, and the torsion rigidity that tends to keep individual tubes straight. We map the energetics of a rope containing twistons onto a lattice gas model and find that the onset of a free "diffusion" of twistons, corresponding to orientational melting, occurs at T_OM > 160 K.Comment: 4 page LaTeX file with 3 figures (10 PostScript files

Development of Shipboard Equipment Shock Survivability Assessment Technique (Continuation)

NPS NRP Executive SummaryDevelopment of Shipboard Equipment Shock Survivability Assessment Technique (Continuation)Chief of Naval Operations (CNO)Naval Sea Systems Command (NAVSEA)This research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Editorial: ONR special issue on multiscale problems of marine composites

The article of record as published may be found at http://dx.doi.org/10.1007/s41939-018-0038-4An editorial for Multiscale and Multidisciplinary Modeling, Experiments and Design, describing upcoming paperson the topic “Composite Materials and Structures for Marine Applications”

Development of Shipboard Equipment Shock Survivability Assessment Technique (Continuation)

NPS NRP Project PosterDevelopment of Shipboard Equipment Shock Survivability Assessment Technique (Continuation)Chief of Naval Operations (CNO)Naval Sea Systems Command (NAVSEA)This research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Expanding Rigid Hull Inflatable Boats (RHIBs) Survivability via Cost-effective Up-armoring

NPS NRP Executive SummarySmall boat crews operating Rigid Hull Inflatable Boats (RHIBs) during Maritime Interdiction Operations (MIO), are often left exposed to adversaries' hostile actions. In conducting Vessel Boarding Search and Seizure (VBSS) and other close-in surface actions boarding teams are prone to gunfire from above, placing them and their small craft at significant risk. While the RHIB is well known for being swift, lightweight, highly maneuverable, and multifunctional, it suffers from an unshielded distant approach, a need for demanding boat handling skills, assumes generally inferior positioning and full exposure while laying alongside larger vessels. To reduce crew casualties and increase RHIB critical component survivability without negatively impacting operational mission success, a cost-effective, lightweight, unencumbering, and easily installable retrofit is needed. This study will investigate appropriate material solutions to protect against small arms, and blast fragmentation effects, while not deterring from the vessel's mission. Additionally, impacts on buoyancy, stability, and other ship's performance characteristics will be studied. Finally, cost and maintenance considerations will be explored as part of the recommended outcomes.N9 - Warfare SystemsThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Impact of Autonomous Robot Assisted Proactive Grooming on Underwater Hull Cleanliness

NPS NRP Executive SummaryShips are continuously under attack from marine growth. This ever-present issue stems from biodiverse micro and macro marine organisms attaching and spreading along the underwater hull surface. While problematic for various reasons it is primarily an issue for Navy vessels due to the serious corrosion effects, unwanted resulting vessel noise signature, constriction of fluid flow through seawater chests, and increased penalties to fuel efficiency. The accumulation of biofoulers increases the hydrodynamic volume and hydrodynamic friction of the ship thus substantially increasing fuel consumption while robbing the ship of power and speed. Management of marine biofouling via proactive underwater ships husbandry not only has the potential to reduce the overall time a ship is in dry-dock but also mitigates these costly detractors while retaining the ship in a more ideal operational status. Aside from the millions of dollars in potential fuel cost savings across the fleet, periodic removal of biological fouling via remotely operated vehicles or through labor-intensive manual grooming methods is shown to reduce the adverse environmental impacts (e.g. CO2 emissions) over-reactive cleaning. Currently, research is underway to better understand the regional and local influence of seawater temperature and impacts associated with biodiversity on the efficacy of proactive grooming. The frequency of the periodic cleaning cycle is also being investigated via testing of submerged hull-plate specimen in multiple geographically diverse locations. This study seeks to address the effectiveness of proactive hull cleaning via further in-depth examination of reported cleaning periodicities and their effects, the applicability to various hull geometries and surface preparations, and/or unique coatings beyond those traditionally used in surface ships. In addition, the authors seek to explore the expanded use of ROV/Autonomous devices performing removal of marine growth on the hull. The correlation of cost benefits tied to recommended proactive cleaning schemes, potential ROV/Autonomous systems and their utilization as part of this periodic underwater ships husbandry approach will be explored through the development of functional relationships and documented in a summary report.Naval Sea Systems Command (NAVSEA)ASN(RDA) - Research, Development, and AcquisitionThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Expanding Rigid Hull Inflatable Boats (RHIBs) Survivability via Cost-effective Up-armoring

NPS NRP Project PosterSmall boat crews operating Rigid Hull Inflatable Boats (RHIBs) during Maritime Interdiction Operations (MIO), are often left exposed to adversaries' hostile actions. In conducting Vessel Boarding Search and Seizure (VBSS) and other close-in surface actions boarding teams are prone to gunfire from above, placing them and their small craft at significant risk. While the RHIB is well known for being swift, lightweight, highly maneuverable, and multifunctional, it suffers from an unshielded distant approach, a need for demanding boat handling skills, assumes generally inferior positioning and full exposure while laying alongside larger vessels. To reduce crew casualties and increase RHIB critical component survivability without negatively impacting operational mission success, a cost-effective, lightweight, unencumbering, and easily installable retrofit is needed. This study will investigate appropriate material solutions to protect against small arms, and blast fragmentation effects, while not deterring from the vessel's mission. Additionally, impacts on buoyancy, stability, and other ship's performance characteristics will be studied. Finally, cost and maintenance considerations will be explored as part of the recommended outcomes.N9 - Warfare SystemsThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Response of dual-layered structures subjected to shock pressure wave

The response of coated, metallic structures subjected to shock pressure waves is studied. The coating is either an elastic material or nearly incompressible rubber of variable stiffness separating the structure from an air or water medium. The stress, nodal velocity, and internal energy of the coated structure are compared to a system without a coating (homogeneous system) to examine the effect of various coating types and configurations on the response of the structure to shock conditions. The results show that a mismatch of impedance, pc0, between the coating and structure governs the degree of energy exchange between the coating and structure at the interface. The impedance mismatch between the structure and a rubber coating at the threshold value is termed the critical difference. If the impedance mismatch exceeds the critical difference, the dynamic response will be more adverse. A softer coating generally has a smaller impedance and tends to concentrate stress wave energy in the underlying structureDefense Nuclear Agency, Alexandria, VAhttp://archive.org/details/responseofdualla00brasMIPR No. 94-573N