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At least 541 records · Page 30

CAST Technical Bulletin #004: Network Time Protocol Introduction

Network Time Protocol (NTP), as it traditionally generated and widely consumed, is a legacy system with known security vulnerabilities. The vulnerabilities can be mitigated by modern implementations of NTP that use internal and external redundancy for better accuracy and fault tolerance. Precision Time Protocol (PTP) is an alternative that uses master clocks inside secure networks to eliminate the known vulnerabilities of NTP.

24 POWER TRANSMISSION AND DISTRIBUTION↗

CAST Technical Bulletin #008: Two-Way Satellite Time and Frequency Transfer (TWSTFT) Setup and Lessons learned

Two-way satellite time and frequency transfer (TWSTFT) has been a trusted time transfer and synchronization method for a long time. It provides good timing accuracy, usually 100 ns or less. The setup of two-way satellite time and frequency transfer (TWSTFT) coordination and communication are crucial to having a system that runs and works as it should, especially when the setup involves traveling and working at a third-party facility. Even with perfect planning, some problems will arise; this document describes TWSTFT setup and lessons learned.

42 ENGINEERING↗

Center for Alternative Synchronization and Timing (CAST) Technical Bulletin #007: Holdover Experiment #1

Stable and accurate timing forms the foundation of many modern essential services. While Global Navigation Satellite Systems (GNSS) provide a cheap way to achieve extremely accurate timing, these systems are vulnerable to interference and complete outages, forcing systems that rely on them into a state of holdover. Testing and characterizing holdover performance is therefore essential for ensuring that these modern services do not go down when GNSS-based timing is unavailable.

24 POWER TRANSMISSION AND DISTRIBUTION↗

Center for Alternative Synchronization and Timing (CAST) Technical Bulletin #006: Holdover Experimental Summary

Stable and accurate timing forms the foundation of many modern essential services. While Global Navigation Satellite Systems (GNSS) provide a cheap way to achieve extremely accurate timing, these systems are vulnerable to interference and complete outages, forcing systems that rely on them into a state of holdover. Testing and characterizing holdover performance is therefore essential for ensuring that these modern services do not go down when GNSS-based timing is unavailable.

24 POWER TRANSMISSION AND DISTRIBUTION↗

Light, High Performance and Scalable Coal-Derived Composites for Construction: Precast and Cast-in-Place Applications

The overall objective of this project was to produce a coal-based construction material that has up to ~95 weight percent (wt. %) coal with physical, chemical, and thermal properties exceeding those of ordinary Portland cement (OPC)-based construction materials. Additionally, the project aimed to minimize external binders by implementing novel mixing techniques, while exceeding the performance/cost ratio of OPC. Finally, the project was to demonstrate production of precast products via the design and fabrication of products via a bench scale process. Consistent with some of these objectives, the project successfully fabricated samples of coal-based composite materials with >80 wt% coal with physical, chemical and thermal properties on par with cement-based concrete. Select samples demonstrated compressive strengths with >7,000 psi and flexural strength of >420 psi. The composite materials minimized external binders and also demonstrated durability, as evidenced by resistance to acidic and basic solutions. Finally, larger slab and beam type samples were produced using a process developed by the Recipient, although, the process was not semicontinuous in nature. Taken together, the results of this project suggest that domestic coal has potential to serve as a replacement for cementitious materials utilized in incumbent construction technologies, which could significantly reduce the energy and emissions of the construction industry

01 COAL, LIGNITE, AND PEAT↗

Stress-corrosion characteristics of aluminum casting alloy M-45

Evaluation of the stress-corrosion characteristics of aluminum alloy M-45 shows that the most favorable artificial aging cycle for this alloy, with regard to optimum strength and stress-corrosion resistance, appears to be 400 degrees F for 12 hours.

Lovoy, C. V.↗

Salvaging surface-damaged aluminum castings

Repair operation for damaged aluminum parts includes anodizing the part, removing the oxide layer, filling the pit or scratch with copper, capping the fill with cadmium, and hand polishing.

Hanna, T. L.↗

Composite casting demonstration

Demonstration was performed to experimentally assess the potential advantages in the processing of materials in space, and specifically, to determine the effects of lack of density segregation and heat convection in the weightless environment of space.

Source record↗

Apollo 14 composite casting demonstration

The purpose of the demonstration was to show that mixtures of materials of different specific gravities would remain stable in the liquid state and during freezing in low g and not segregate as they do on earth. An inflight demonstration was performed on the Apollo 14 mission during the translunar and and transearth coast periods. The apparatus consisted of an electrical heater, a heat sink device for cooling, and sealed metal capsules containing matrix materials having a low-melting point and dispersants. The evaluation of the demonstration samples was accomplished by comparing space processed (flight) samples with (control) samples processed on the ground under otherwise similar conditions. In the low q environment of space flight the dispersions of particles, fibers, and gases in a liquid metal matrix were maintained during solidification. Dispersions of normally immiscible liquids were also maintained during solidification.

Yates, I. C., Jr.↗

Acoustic testing of a supersonic tip speed fan with acoustic treatment and rotor casting slots. Quiet engine program scale model fan C

Acoustic tests were conducted on a high tip speed (1550 ft/sec, 472.44 m/sec) single stage fan with varying amounts of wall acoustic treatment and with circumferential slots over the rotor blade tips. The slots were also tested with acoustic treatment placed behind the slots. The wall treatment results show that the inlet treatment is more effective at high fan speeds and aft duct treatment is more effective at low fan speeds. Maximum PNL's on a 200-foot (60.96 m) sideline show the untreated slots to have increased the rear radiated noise at approach. However, when the treatment was added to the slots inlet radiated noise was decreased, resulting in little change relative to the solid casing on an EPNL basis.

Kazin, S. B.↗

Dynamic oxidation behavior at 1000 and 1100 C of four nickel-base cast alloys, NASA-TRW VIA, B-1900, 713C, and 738X

The superalloys NASA-TRW VIA, B-1900, 713C, and 738X were tested cyclically and isothermally for resistance to oxidation in high velocity gas streams for 100 hours at specimen temperatures of 1000 C and 1100 C. Alloys VIA and B-1900, which were the most oxidation resistant, displayed slight and very similar weight changes and metal losses. Alloy 713C also sustained only slight metal losses, but it exhibited some tendency to spall. Alloy 738X was found to be the most susceptible to cyclic oxidation; this resulted in heavy spalling, which in turn caused high weight losses and high metal losses. Oxidation test results are related to the amounts of chromium aluminum, and the refractory metals in the alloys investigated.

Sanders, W. A.↗