Qualitative and quantitative analysis of trace substances determined by Mass spectrometry has unique advantages which can¡¦t be replaced. For example, the detection limit of common gas sensors are difficult to lower than 1 ppm, and the sensitivity, selectivity, period of use and stability are not ideal. The detection limit of mass spectrometer is general low to 0.01 ppm. Furthermore, all substances in the sample can be simultaneous analysis by mass spectrometer, but single gas sensor measurements cannot. In this study, dielectric barrier discharge plasma is used in environmental mass spectrometry analysis. This study develops an innovative balanced T-shaped dielectric barrier discharge (DBD) plasma generator for generating atmospheric plasma to replace the linear type plasma generator. Through the change of the geometric configuration and the drive phase develop T-shaped dielectric barrier discharge plasma, the balanced design can fully cancel the high potential and noise. The main objective of this study for the more traditional linear electrodes of the study's original novel T-shaped electrodes of different, including mass spectrometry, spectroscopy, and some basic electrical measurements, and by changing the electrode design, voltage, temperature, gas flow, gas flow rate, diameter and other parameters of the dielectric, and compare their differences and to explore the most suitable parameters. The results showed that T-shaped design of the research and development of innovation through the elimination of the exit pressure put EFI flame can indeed significantly reduce sample oxidation and generate fragments of the situation, and thus improve the mass spectrum of readability and debris interference, thus improving the detection limit , especially for some with a benzene ring and long-chain carbon samples. The experimental results confirm that the development of the Institute of Atmospheric Pressure Plasma free system can be prolonged to produce high concentrations of plasma gas as a free source of the mass spectrometry system, and provides more than 107 cm-3 ion concentration. MS-free analysis of the system can be directly on the gas, liquid and solid samples, the test do not need complicated traditional mass spectrometry analysis of the required sample pre-treatment steps, you can get a clear identification of high mass spectrometry signal. In addition to introducing the basic principles and structure of the atmospheric pressure plasma discharge device, and take advantage of many samples test for the different plasma mass spectrometry free system performance verification.

<p>  </p> <p>In the time after their conception, Dielectric Barrier Discharge (DBD) systems have become highly utilized in the field of plasma research, with applications ranging from medicine to water treatments to airfoil design. One of the more recent applications for DBD systems has been the plasma treatment of polymers, overcoming the deficits of previously used chemical treatment systems such as environmental hazards, high cost, and other complexities. A novel development occurring within the past three years was the use of a DBD system to treat the inner surface of small-diameter polymer tubing to improve the wettability and adhesion characteristics as compared to untreated polymer tubing. This work is interested in improving that DBD system.</p> <p>This thesis focuses on the development and implementation of two additional systems for an atmospheric pressure DBD system that treats the inner surface of narrow-diameter polymer tubes. The first, a pulsed-DC HV generator, will improve the plasma treatment. The fast rise times of the applied voltage prevent any stochastic behavior in plasma ignition and reignition, the resulting homogeneity of the plasma means that the plasma conditions of the treatment are more easily reproduced, and the increase in plasma intensity allows for quicker treatment of the tubing, the feed rates can reach the level of industrial production without lessening the effects induced by the treatment. The second, a Capstan-driven spooling system, will also improve the industrial capabilities of the DBD system. The higher feed rates that the spooling system reaches provide a means to rapidly produce treated tubing at a continuous rate, and the user-friendly interface means that system operation increases to a broader range of potential personnel. </p> <p>Investigation of the effect that tube feed rate (plasma exposure time) has on surface wettability was performed for the feed rates of the spooling systems. Feed rates of 2.5, 10, 50, 200, and 800 mm/min were performed on tubing samples for a 100% Helium plasma at a power level of 5 mW and a 98%He-2%O2 plasma at a power level of 20 mW. The temporal evolution of wettability was determined by taking the water contact angle (θ) of the treated tubing surface 0, 1, 2, 4, 16, 24, and 120 hours after plasma treatment. The resulting water contact angles initially fluctuate but eventually decay to reach a steady-state hydrophilicity that remains up to five days. The steady-state contact angles ranged from 42.3o < θss < 70.2o for a Helium plasma and 39.9o < θss < 62.7o for a Helium-Oxygen plasma. </p> <p>Investigation of the plasma power achieved with a pulsed-DC HV generator was also performed. The pulsed DC-driven plasma, which has a characteristic rise time of ~300 ns, ignites at Vbd = 4.5 kV. This breakdown voltage is 1.3 times higher than the minimum for the system, Vbd,min = 3.45 kV, so the resulting overvoltage of the pulsed-DC generator is approximately 1.3 times the minimum breakdown voltage. The electrical power deposited to the discharge for the pulsed-DC driven discharge (133.2 mW) is 6 times the power of the previous AC-driven discharge (21.4 mW). Resulting surface wettability was also calculated for the two generators. The stronger plasma treatment of the pulsed-DC HV generator resulted in a steady-state contact angle 11.4o more hydrophilic than the AC HV generator (θss = 44.6o for pulsed-DC-driven discharge compared to θss = 56o for AC-driven discharge).</p>

No description available.

Background: Bacterial contamination of surfaces with methicillin-resistant Staphylococcus aureus (MRSA) is a serious problem in the hospital environment and is responsible for significant nosocomial infections. The pathogenic contaminants form biofilms, which are difficult to treat with routine biocides. Thus, a continuous search for novel disinfection methods is essential for effective infection control measures. This demonstration of a novel technique for the control of virulent pathogens in planktonic form as well as in established biofilms may provide a progressive alternative to standard methodology. Methods: We evaluated a novel technique of normal atmospheric nonthermal plasma known as floating-electrode dielectric-barrier discharge (FE-DBD) plasma against a control of planktonic and biofilm forms of Escherichia coli, S aureus, multidrug-resistant methicillin-resistant S aureus (MRSA) -95 (clinical isolate), -USA300, and -USA400, using widely accepted techniques such as colony count assay, LIVE/DEAD BacLight Bacterial Viability assay, and XTT (2,3-Bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) assay. Results: Exposure of free living planktonic forms of E coli, S aureus, and MRSA were rapidly inactivated by DBD plasma. Approximately 107 bacterial cells were completely (100%) killed, whereas 108 and 109 were reduced by approximately 90% to 95% and 40% to 45%, respectively, in less than 60 seconds (7.8 J/cm2) and completely disinfected in ≤120 seconds. In established biofilms, the susceptibility of MRSA USA400 was comparable with USA300 but less susceptible than MRSA95 (clinical isolate), S aureus, and E coli (P < .05) to FE-DBD plasma, and plasma was able to kill MRSA more than 60% within 15 seconds (1.95 J/cm2). The killing responses were plasma exposure-time dependent, and cell density dependent. The plasma was able disinfect surfaces in a less than 120 seconds. Conclusion: Application of DBD plasma can be a valuable decontamination technique for the removal of planktonic and biofilm-embedded bacteria such as MRSA -USA 300, -USA 400, methicillin-sensitive S aureus (MSSA), and E coli, the more common hospital contaminants. Of interest, E coli was more resistant than S aureus phenotypes.

No description available.

The combustor-diffuser system remains one of the most studied sections of the turbomachine. Most of these investigations are due to the fact that quite a bit of flow diffusion is required in this section as the high speed flow exits the compressor and must be slowed down to enter the combustor. Like any diffusion process there is the chance for the development of an unfavorable adverse pressure gradient that can lead to flow separation; a cause of drastic losses within a turbine. There are two diffusion processes in the combustor-diffuser system: The flow first exits the compressor into a pre-diffuser, or compressor discharge diffuser. This diffuser is responsible for a majority of the pressure recovery. The flow then exits the pre-diffuser by a sudden expansion into the dump diffuser. The dump diffuser comprises the majority of the losses, but is necessary to reduce the fluid velocity within acceptable limits for combustion. The topic of active flow control is gaining interest in the industry because such a technique may be able to alleviate some of the requirements of the dump diffuser. If a wider angle pre-diffuser with separation control were used the fluid velocity would be slowed more within that region without significant losses. Experiments were performed on two annular diffusers to characterize the flow separation to create a foundation for future active flow control techniques. Both diffusers had the same fully developed inlet flow condition, however, the expansion of the two diffusers differed such that one diffuser replicated a typical compressor discharge diffuser found in a real machine while the other would create a naturally separated flow along the outer wall. Both diffusers were tested at two Reynolds numbers, 5x104 and 1x105, with and without a vertical wall downstream of the exit to replicate the dump diffuser that re-directs the flow from the pre-diffuser outlet to the combustor. Static pressure measurements were obtained along the OD and ID wall of the diffusers to determine the recovered pressure throughout the diffuser. In addition to these measurements, tufts were used to visualize the flow. A turbulent CFD model was also created to compare against experimental results. In the end, the results were validated against empirical data as well as the CFD model. It was shown that the location of the vertical wall was directly related to the amount of separation as well as the separation characteristics. These findings support previous work and help guide future work for active flow control in a separated annular diffuser both computationally and experimentally.