In Situ Raman Spectroscopy for Early Corrosion Detection in Coated AA2024-T3.

Here we describe the synthesis and evaluation of a molecular corrosion sensor that can be applied in situ in aerospace coatings, then used to detect corrosion after the coating has been applied. A pH-sensitive molecule, 4-mercaptopyridin (4-MP), is attached to a gold nanoparticle to allow surface-enhanced Raman-scattering (SERS) for signal amplification. These SERS nanoparticles, when combined with an appropriate micron-sized carrier system, are incorporated directly into an MIL-SPEC coating and used to monitor the process onset and progression of corrosion using pH changes occurring at the metal-coating interface.

Thermoelectric Energy Harvesting for Exhaust Waste Heat Recovery: A System Design.

Thermal energy harvesting for high-speed moving objects is particularly promising in providing an efficient and sustainable energy source to enhance operational capabilities and endurance. Thermoelectric (TE) technology, by exploiting temperature gradients between a heat source and ambient temperature, can provide a continuous power supply to such systems, reducing the reliance on conventional batteries and extending operation times. However, the integrated thermoelectric generator (TEG) system design research is far behind materials development.

Unusually high room and elevated-temperature tensile properties observed in direct aged wire-arc directed energy deposited Inconel 718.

Wire-arc directed energy deposition (DED) processed Inconel (IN) 718 is known to have coarse columnar grains, strong texture, and significant chemical and microstructural inhomogeneity in the as-fabricated condition. Homogenization treatment is commonly used prior to aging to eliminate the inhomogeneity and detrimental precipitation for better mechanical properties. In this study, however, direct aging (DA) at 700 °C without homogenization has resulted in room-temperature yield strength, ultimate tensile strength (UTS), and elongation that are comparable to wrought condition and among the highest reported properties for wire-arc DED IN718.

Defect-Engineering-Stabilized AgSbTe with High Thermoelectric Performance.

Thermoelectric (TE) generators enable the direct and reversible conversion between heat and electricity, providing applications in both refrigeration and power generation. In the last decade, several TE materials with relatively high figures of merit (zT) have been reported in the low- and high-temperature regimes. However, there is an urgent demand for high-performance TE materials working in the mid-temperature range (400-700 K).

A universal all-solid synthesis for high throughput production of halide perovskite.

Halide perovskites show ubiquitous presences in growing fields at both fundamental and applied levels. Discovery, investigation, and application of innovative perovskites are heavily dependent on the synthetic methodology in terms of time-/yield-/effort-/energy- efficiency. Conventional wet chemistry method provides the easiness for growing thin film samples, but represents as an inefficient way for bulk crystal synthesis.

Recommendation on Orbiting Sample Cleanliness.

The National Aeronautics and Space Administration-European Space Agency (NASA-ESA) Mars Sample Return (MSR) campaign involves the collection of samples on Mars by the Perseverance (Mars 2020) rover and their return to Earth. To accomplish this, the Orbiting Sample container (OS) will be sent to Mars to accommodate the collected samples then launched from Mars and returned to Earth, where the samples will be removed for examination in the Sample Return Facility (SRF). Crucial to this entire sequence will be establishment of the required level of cleanliness inside the OS.

Bio-inspired strategies for next-generation perovskite solar mobile power sources.

Smart electronic devices are becoming ubiquitous due to many appealing attributes including portability, long operational time, rechargeability and compatibility with the user-desired form factor. Integration of mobile power sources (MPS) based on photovoltaic technologies with smart electronics will continue to drive improved sustainability and independence. With high efficiency, low cost, flexibility and lightweight features, halide perovskite photovoltaics have become promising candidates for MPS.

Electrocaloric Performance of Multilayer Ceramic Chips: Effect of Geometric Structure Induced Internal Stress.

Driven by an ever-growing demand for environmentally benign cooling systems, the past decade has witnessed the booming development in the field of electrocaloric (EC) cooling technology, which is considered as a promising solid-state cooling approach. Multilayer ceramic chip capacitors (MLCCs) represent the optimum structure for EC cooling elements because of large breakdown strengths, low driving voltages, and high macroscopic volumes of active EC materials. However, fundamental relationships between the geometric parameters of MLCCs and the EC coefficient are less understood.

Universal Multienergy Harvester Architecture.

The energy available in the ambient vibrations, magnetic fields, and sunlight can be simultaneously or independently harvested using universal architecture. The universal harvester design is shown to effectively convert ambient magnetic fields, vibration, and light into electricity. The architecture is composed of a perovskite solar cell integrated onto a magnetoelectric composite cantilever beam.

Effects of flow recirculation on acoustic and dynamic measurements of rotary-wing systems operating in closed anechoic chambers.

An experimental campaign was undertaken to identify the effects posed by flow recirculation on the dynamic performance and acoustic emissions of an isolated rotor, operating in hover in a sealed anechoic chamber. It is shown that flow recirculation is an artifact of testing rotary-wing systems in an enclosed environment, and results in a significant amplification of tonal and broadband noise components. The acoustic emissions produced while the recirculated flow is ingested into the rotor disk vary from those emitted by similar rotors operating in clean inflow conditions.

Exact analytic solution for a chaotic hybrid dynamical system and its electronic realization.

A novel hybrid dynamical system comprising a continuous and a discrete state is introduced and shown to exhibit chaotic dynamics. The system includes an unstable first-order filter subject to asynchronous switching of a set point according to a feedback rule. Regular samples of the continuous state yield a one-dimensional return map that is a tent function.

Widely tunable compact terahertz gas lasers.

The terahertz region of the electromagnetic spectrum has been the least utilized owing to inadequacies of available sources. We introduce a compact, widely frequency-tunable, extremely bright source of terahertz radiation: a gas-phase molecular laser based on rotational population inversions optically pumped by a quantum cascade laser. By identifying the essential parameters that determine the suitability of a molecule for a terahertz laser, almost any rotational transition of almost any molecular gas can be made to lase.

Laser-sculptured ultrathin transition metal carbide layers for energy storage and energy harvesting applications.

Ultrathin transition metal carbides with high capacity, high surface area, and high conductivity are a promising family of materials for applications from energy storage to catalysis. However, large-scale, cost-effective, and precursor-free methods to prepare ultrathin carbides are lacking. Here, we demonstrate a direct pattern method to manufacture ultrathin carbides (MoC, WC, and CoC) on versatile substrates using a CO laser.

Quantitative analysis of gas phase molecular constituents using frequency-modulated rotational spectroscopy.

Rotational spectroscopy has been used for decades for virtually unambiguous identification of gas phase molecular species, but it has rarely been used for the quantitative analysis of molecular concentrations. Challenges have included the nontrivial reconstruction of integrated line strengths from modulated spectra, the correlation of pressure-dependent line shape and strength with partial pressure, and the multiple standing wave interferences and modulation-induced line shape asymmetries that sensitively depend on source-chamber-detector alignment. Here, we introduce a quantitative analysis methodology that overcomes these challenges, reproducibly and accurately recovering gas molecule concentrations using a calibration procedure with a reference gas and a conversion based on calculated line strengths.

A descriptive study of US Special Operations Command fatalities, 2001 to 2018.

Background: Studies of fatalities from injury and disease guide prevention and treatment efforts for populations at risk. Findings can inform leadership and direct clinical practice guidelines, research, and personnel, training, and equipment requirements.

Methods: A retrospective review and descriptive analysis was conducted of United States Special Operations Command (USSOCOM) fatalities who died while performing duties from September 11, 2001, to September 10, 2018.

Ultra-high performance wearable thermoelectric coolers with less materials.

Thermoelectric coolers are attracting significant attention for replacing age-old cooling and refrigeration devices. Localized cooling by wearable thermoelectric coolers will decrease the usage of traditional systems, thereby reducing global warming and providing savings on energy costs. Since human skin as well as ambient air is a poor conductor of heat, wearable thermoelectric coolers operate under huge thermally resistive environment.

Air transport of patients with severe lung injury: development and utilization of the Acute Lung Rescue Team.

Background: Critical Care Air Transport Teams (CCATTs) are an integral component of modern casualty care, allowing early transport of critically ill and injured patients. Aeromedical evacuation of patients with significant pulmonary impairment is sometimes beyond the scope of CCATT because of limitations of the transport ventilator and potential for further respiratory deterioration in flight. The Acute Lung Rescue Team (ALRT) was developed to facilitate transport of these patients out of the combat theater.

Perception-action icons: an interface design strategy for intermediate domains.

Objective: A prototype interface was developed to support decision making during tactical operations; a laboratory experiment was conducted to evaluate the capability of this interface to support a critical activity (i.e., obtaining the status of friendly combat resources).