Depriming of arterial heat pipes: An investigation of CTS thermal excursions

Four thermal excursions of the Transmitter Experiment Package (TEP) were the result of the depriming of the arteries in all three heat pipes in the Variable Conductance Heat Pipe System which cooled the TEP. The determined cause of the depriming of the heat pipes was the formation of bubbles of the nitrogen/helium control gas mixture in the arteries during the thaw portion of a freeze/thaw cycle of the inactive region of the condenser section of the heat pipe. Conditions such as suction freezeout or heat pipe turn-on, which moved these bubbles into the active region of the heat pipe, contributed to the depriming mechanism. Methods for precluding, or reducing the probability of, this type of failure mechanism in future applications of arterial heat pipes are included

CTS-type variable conductance heat pipes for SEP FM/PPU

The development effort for, and the fabrication and testing of, six CTS-type variable conductance heat pipes is described. The heat pipes are constructed of stainless steel, use methanol as a working fluid, and a nitrogen/helium mixture as the control gas. The wicking structure consists of interior wall grooves, a metal-felt diametral slab wick, and two wire-mesh arteries. The heat pipes are used to cool two Functional Model/Power Processing Units in a Solar Electric Propulsion prototype BIMOD thruster subsystem assembly. The Power Processing Units convert the electric power from a spacecraft solar array system to the voltages required to operate the electric thrusters which are part of the BIMOD assembly

Heat pipe life and processing study

The merit of adding water to the reflux charge in chemically and solvent cleaned aluminum/slab wick/ammonia heat pipes was evaluated. The effect of gas in the performance of three heat pipe thermal control systems was found significant in simple heat pipes, less significant in a modified simple heat pipe model with a short wickless pipe section. Use of gas data for the worst and best heat pipes of the matrix in a variable conductance heat pipe model showed a 3 C increase in the source temperature at full on condition after 20 and 246 years, respectively

Extended Development of Variable Conductance Heat Pipes

A high-capacity vapor-modulated heat pipe was designed and tested. In 1977, a program was undertaken to use the aforementioned heat pipe to study protection from freezing-point failure, increase control sensitivity, and transient behavior under a wide range of operating conditions in order to determine the full performance potential of the heat pipe. A new concept, based on the vapor-induced-dry-out principle, was developed for passive feedback temperature control as a heat pipe diode. This report documents this work and describes: (1) the experimental and theoretical investigation of the performance of the vapor-modulated heat pipe; and (2) the design, fabrication and test of the heat pipe diode

ВПЛИВ ЛАТИНСЬКОЇ ШКОЛИ НА РОЗВИТОК ШКІЛЬНОЇ ОСВІТИ УКРАЇНИ

The article examines social and historical backgrounds of establishment and formation of secondary education in Ukraine in the XVI – XVII centuries. Role of Western-style schools like Jesuit and Protestant schools in this educational system is outlined and role of the Latin language as a tool for learning and knowledge transfer in the Eastern Slavic area is emphasized. Historical and pedagogical processes are described in terms of national traditions, which were based on the educational achievements of Kievan Rus and West European accomplishments.У статті розглядаються соціально-історичні передумови становлення й формування шкільної освіти в Україні в період XVI – XVII ст., показано місце шкіл західного зразка - єзуїтських, протестантських у цій системі, підкреслено роль латинської мови як інструменту засвоєння й передачі знань у східнослов’янському просторі. Історико-педагогічний процес охарактеризовано з точки зору національної традиції, яка, базуючись на освітніх досягненнях Київської Русі, була зорієнтованою на західноєвропейські здобутки

A theoretical model for estimation of work function reduction for MXenes with hydroxyl termination

This article presents a simple model that explains significant reduction of work function in MXenes Тіn+1Сn with hydroxyl termination and demonstrates matching results to ones in the existing literature, obtained via complex computing based on the first principles. This model can be applied for results evaluation of the hydroxyfunctionalization of various MXene types, due to prospects of the creation of novice emission electronics devices

Colloidal aggregation in microgravity by critical Casimir forces

By using the critical Casimir force, we study the attractive strength dependent aggregation of colloids with and without gravity by means of Near Field scattering. Significant differences were seen between microgravity and ground experiments, both in the structure of the formed fractal aggregates as well as the kinetics of growth. Ground measurements are severely affected by sedimentation resulting in reaction limited behavior. In microgravity, a purely diffusive behavior is seen reflected both in the measured fractal dimensions for the aggregates as well as the power law behavior in the rate of growth. Formed aggregates become more open as the attractive strength increases.Comment: 4 pages, 3 figure

Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation

In the photosynthetic photosystem II, electrons are transferred from the manganese-containing oxygen evolving complex (OEC) to the oxidized primary electron-donor chlorophyll P680•+ by a proton-coupled electron transfer process involving a tyrosine-histidine pair. Proton transfer from the tyrosine phenolic group to a histidine nitrogen positions the redox potential of the tyrosine between those of P680•+ and the OEC. We report the synthesis and time-resolved spectroscopic study of a molecular triad that models this electron transfer. The triad consists of a high-potential porphyrin bearing two pentafluorophenyl groups (PF10), a tetracyanoporphyrin electron acceptor (TCNP), and a benzimidazole-phenol secondary electron-donor (Bi-PhOH). Excitation of PF10 in benzonitrile is followed by singlet energy transfer to TCNP (τ = 41 ps), whose excited state decays by photoinduced electron transfer (τ = 830 ps) to yield Bi-PhOH-PF 10•+-TCNP•-. A second electron transfer reaction follows (τ < 12 ps), giving a final state postulated as BiH+-PhO•-PF10-TCNP•-, in which the phenolic proton now resides on benzimidazole. This final state decays with a time constant of 3.8 μs. The triad thus functionally mimics the electron transfers involving the tyrosine-histidine pair in PSII. The final charge-separated state is thermodynamically capable of water oxidation, and its long lifetime suggests the possibility of coupling systems such as this system to water oxidation catalysts for use in artificial photosynthetic fuel production.Fil: Megiatto, Jackson D.. Arizona State University; Estados UnidosFil: Antoniuk Pablant, Antaeres. Arizona State University; Estados UnidosFil: Sherman, Benjamin D.. Arizona State University; Estados UnidosFil: Kodis, Gerdenis. Arizona State University; Estados UnidosFil: Gervaldo, Miguel Andres. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Moore, Thomas A.. Arizona State University; Estados UnidosFil: Moore, Ana L.. Arizona State University; Estados UnidosFil: Gust, Devens. Arizona State University; Estados Unido