Comparative studies of conceptual design and qualification procedures for a Mars probe/lander. Volume III - Probe, entry from orbit. Book 3 - Development test programs Final report

Subsystem development status and ground development tests for Mars probe and recommended flight test

Lethal Effects of Pulsed High-Voltage Discharge on Marine Plankton and Escherichia coli

Abstract Ballast seawater is considered globally as a major vector for invasions of non-indigenous organisms. Several technologies have been tested for their ability to remove organisms from ballast water. In the present study, we constructed a novel pulsed high-voltage discharge (PHVD) system that could operate in either high current mode with several hundred amperes or shockwave generating mode with relatively lower current in seawater. In laboratory-scale experiments, the PHVD system with shockwave-generating mode was found to be more effective in killing zooplankton (1.9-to 4.0-fold) and phytoplankton (3.3-fold) than high current mode at discharge with 300-500 pulses at 7.1 kV. Further experiments were carried out at different voltages and pulse-numbers to examine effects of the shockwave-generating PHVD system on viabilities of one zooplankton larva, two phytoplankton species, and an indicator bacterium suspended in seawater in a static chamber. For zooplankton, live cells were not detected at discharge with 400 pulses at 13 kV. For phytoplankton, the initial live cells of a dinoflagellate was decreased by 77±0.5%, and the initial chl a concentration of a diatom was decreased by 76±6% at discharge with 700 pulses at 13 kV. For an indicator bacterium Escherichia coli, live cells were not detected at discharges with 200 or 700 pulses at 13 kV. Measurements of ATP content of organisms showed congruent results with those obtained by the above methods, suggesting it may be a rapid method for evaluating treatment efficiency. Though further scale-up studies are necessary, these results suggest that the PHVD system have a high potential for applying to ballast seawater treatment

Index to NASA tech briefs, 1971

The entries are listed by category, subject, author, originating source, source number/Tech Brief number, and Tech Brief number/source number. There are 528 entries

Design and Fabrication of Carbon Nanotube Array based Field Emission Cathode for X-ray Tube

Field emission cathodes have proven themselves to be excellent candidates for some special medical X-ray applications. Spindt cathode and CNT (carbon nanotube) based field emission cathode have been widely studied for many years. Spindt cathode has the near perfect structure, but the material property limits its applications. On the other hand, low density vertically aligned CNT array has been proved the best candidate of field emission material. Several attempts have been made to combine the advantages of the Spindt cathode and CNT array, but some most important advantages of Spindt cathode have not been successfully utilized in CNT emitter design, for example: ballast resistor, self-aligned fabrication process, sub-micron scale gate electrode, and low control voltage. In this thesis, the design, fabrication and test of CNT based field emission cathode with a novel ballast resistor and coaxial cylinder shape gate electrode is reported. A connection pad has been reported for the first time. This structure makes the ballast resistor can be utilized in a CNT field emitter array. Therefore, the uniformity and stability of field emission current is improved significantly. In addition, the stabilized emission current heated up the sample to a high temperature and changes the emission from field emission to Schottky emission regime. This is the first report of the self-heating Schottky emission from a CNT emitter array. Coaxial cylinder shape gate electrode is another important improvement in the CNT emitter design. The gate electrode adopts the self-alignment property of the Spindt cathode, and adjusted to fit the structure and synthesis process of CNT array. This new design and fabrication process has all the advantages of both the Spindt cathode and CNT emitter. In addition to the field emission cathode design, a novel PMMA (poly methyl methacrylate) based FEM (field emission microscope) is designed to evaluate the emission uniformity and capture high resolution images of the distribution of field emitted electrons. Compare to the conventional phosphor screen based FEM, the PMMA based FEM has a much higher resolution and sensitivity. Images of this new FEM have a resolution of as high as 0.34 nm and clearly show the boundary of crystal facets.1 yea

Comparative study of approved imo technologies for treatment of ballast waters

Worldwide fleet has continuously been growing during last years, using ballast water almost all of the vessels and increasing the risk of spread of invasive species into local environments. The risk of invasion has pushed the International Maritime Organization to legislate the control and treatment of ballast water to minimize the risks. For this reason, the International Convention for the Control and Management of Ships’ Ballast Water and Sediments has played an essential role for achieving a proper control of the ballasting and de-ballasting process. After the different regulations included on the Convention, many Ballast Water Management Systems (BWMS) have been approved. The different treatment systems have clearly reduced ballast water impact but the only way for reducing completely the risk of invasion is to reduce the use of ballast water and to design alternative methods. Therefore, the international organizations should act for accomplish the reduction of ballast water usage in the near future and to motivate maritime industry to invest and to study new free-ballast vessel design. The methodology used during the paper consists on a deep theorical explanation of the ballast water impact (including Ballast Water Management Convention) and a comparison among four different BWMS. The aim of the comparison is to distinguish which system is best regarding the friendliness to the environment and the efficiency for the vessel. After the comparison, different proposals for improving the ballast water impact will be explained to understand how the risk can be even more reduced

Developing an experimental setup for Thunder Bay waste pollution control plant (WPCP) to evaluate UV lamp performance

An automated experimental setup was developed to measure the spectral irradiance of new low pressure (LP) ultraviolet lamp (UV). The experimental analysis was performed by the measurement of the UV intensity along the length of the lamp to evaluate the variation in UV output during preliminary 5% lifespan of the UV lamp. The automation of the experimental setup has executed with the Arduino-LabVIEW interfaced computer program to maintain sequential collaboration among the setup components. The new LP UV lamp had a non-uniform output with the unexpected rise and drop in the UV intensity at certain locations along the length. The lamp showed predominant ageing signs at the electrode, which was confirmed by the visual observation after the appearance of the darken quartz sleeve near the electrode and further reduction in UV output was verified by the experimental analysis as a result of the obstructed transmittance of the UV radiation through the quartz sleeve. Initially, UV output of the new lamp was uniform; however, as the lamp was aged analysis noticed non-uniform output along the length of the lamp though the lamp was operated for same working conditions throughout the entire experimental phase. The non-uniform temperature profile of the UV lamp was studied with the implementation of the thermal imaging IR camera to confirm variable temperature gradient inside the quartz sleeve and at the surface of the quartz sleeve. The thermal analysis recognized the overheating of the lamp electrode. Further, as amp aged the temperature profile at the lamp electrode raised significantly. The experimental analysis proved that the lamp ageing was more noticeable at lamp ends than the middle part of the lamp, which was confirmed after evaluation of the UV intensity along the length of the lamp as well as after performing the output stability test at electrode for corresponding lamp operating cycle

Study of Periodic Forcing with a Dielectric Barrier Discharge Device for the Control of Flow Separation on a NACA 0012

The continued high global demand for passenger and freight air traffic as well as increased use of unmanned aerial vehicles (UAVs), in spite of rising fuel costs and several tragic cases involving loss-of-control events, has resulted in researchers examining alternative technologies, which would result in safer, more reliable, and superior performing aircraft. Aerodynamic flow control may be the most promising approach to this problem having already proven its ability to enable higher flow efficiency while also simultaneously improving overall flow control. Recent research in the area of aerodynamic control is transitioning from traditional mechanical flow control devices such as slats and flaps to plasma actuators. Plasma actuators offer an inexpensive and energy efficient method of flow control. In addition, plasma actuator technology has the potential of application to a host of other aircraft performance parameters including applications in radar mitigation and in situ wing deicing.;Dielectric Barrier Discharge (DBD), one of the most widely studied forms of plasma actuation, employs an electrohydrodynamic (EHD) device, which uses dominant electric fields and the respective electrically related body forces for actuation. Unlike momentum jets or other traditional flow control methods used on wings and tail surfaces, a DBD device operates without moving components or injecting any mass into the flow stream.;Work performed focuses on qualitatively investigating experimentally the use of DBD devices for flow separation control on a NACA 0012-based 2D wing model. Flow visualization techniques illuminated flow seed particles around the model to determine the state of the flow (i.e., attached or separated) for various actuator cases. The DBD was operated in a steady-on mode as well as for three different pulsing frequencies (only for low power testing) based on the Strouhal frequency for each flight condition and compared to the clean (i.e., plasma off) case. Some of the flow control results were compared to another active flow control scheme known as dynamic roughness (DR) which consists of surface mounted time dependent deforming elements that operate as a periodic forcing device that energizes the boundary layer. The potential use of DBDs for application to existing UAVs and aircraft was also evaluated based on applicability, power consumption, and other relevant factors.;Results of this work indicate that low power gapless DBD actuators are an effective form of separation control at low Reynolds numbers Ohorn (10 4) near the angle of attack where separation begins to occur. However, testing seems to indicate that gapless low power DBDs are underpowered to have any substantial flow control authority at higher Reynolds numbers and angles of attack. With improved materials for DBD construction and more testing, DBDs could potentially be an effective form of flow control on UAVs and manned aircraft in the future

Understanding the inactivation mechanism of foodborne pathogens using cold atmospheric plasma

Experimental studies into the use of cold atmospheric plasmas for inactivating foodborne pathogens are presented in this thesis. Eliminating the possibility that treatment delivered by a plasma to a population or assemblage of micro-organisms is unevenly distributed is an essential pre-requisite to attempting to interpret inactivation kinetics with a view to elucidating mechanisms of inactivation. A filtration method of depositing cells evenly on the surface of a membrane without cell stacking was developed and used throughout the work described here. Two atmospheric plasma systems were evaluated and each brought about microbial inactivation in a distinct way. A pulsed radio frequency plasma jet operated at 3.47 MHz caused gross morphological changes to L. innocua whereas a low frequency air mesh plasma system operated at a frequency of 24 kHz led to the inactivation of these bacteria without inducing observable structural changes. Changing the operating parameters of the plasma jet system had a significant effect on the composition of the reactive plasma species generated as revealed by changes to the mode of inactivation of bacteria. In addition to inactivating bacteria, the pulsed plasma jet was shown to be highly effective in degrading and removing amyloid aggregates from the surface of mica coupons. Amyloids have widely been used as a non-infectious model for prions, and the results obtained here show potential for the application of gas plasma technology for removing prions from abiotic surfaces in medical and other applications. It has widely been assumed that bacterial envelopes are the principal sites at which reactive plasma species bring about damage to cells. However, changing the composition of the bacterial membranes of E. coli and Listeria innocua by cultivating them at widely different temperatures to induce changes proved not to result in enhanced inactivation. Flow cytometry was also used to provide additional insights into possible mechanisms of inactivation. The following fluorescent dyes were used either singly or in combination; SYTO 13, DiBAC4(3), cFDA and PI. The results obtained with the dyes DiBAC4(3) and PI showed that Gram positive bacteria became depolarised prior to the bacterial membrane becoming compromised, possibly suggesting that the inactivating plasma species are affecting membrane proteins responsible for maintaining the bacterial charge. Differences between the fluorescent dye staining of Gram negative and Gram positive species were obtained using SYTO13 and PI demonstrating that the different membrane structures affect their interaction with the plasma. In additional studies, the air mesh plasma was used to treat multi-drug resistant strains of Methicillin resistant Staphylococcus aureus (MRSA) in an attempt to reverse antibiotic resistance. MRSA PM 64 was shown to reverse its antibiotic resistance to Oxacillin, Kanamycin and Trimethoprim. Culturing the bacteria in a nutrient limited media led to increased resistance towards plasma treatment and maintenance of their high levels of antibiotic resistance