Dissertations / Theses: 'Air gap'

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Carrara, Brent. "Air-Gap Covert Channels." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35103.

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A fresh perspective on covert channels is presented in this work. A new class, air-gap covert channels, is defined as an unintentional communication channel established between systems that are physically and electronically isolated from one another. A specific class of air-gap covert channel is studied in depth, out-of-band covert channels (OOB-CCs), which are defined as policy-breaking communication channels established between isolated, physically unmodified systems. It is shown that OOB-CCs can be categorized by the physical channel that they communicate over: acoustic, light, seismic, magnetic, thermal, and radio-frequency, and the hardware that is required at the transmitter and receiver to make covert communication possible. In general, OOB-CCs are not as high-bandwidth as conventional radio-frequency channels; however, they are capable of leaking sensitive information that requires low data rates to communicate (e.g., text, recorded audio, cryptographic key material). The ability for malware to communicate information using a specific type of OOB-CC, the covert-acoustic channel, is also analyzed. It is empirically demonstrated that using physically unmodified, commodity systems (e.g., laptops, desktops, and mobile devices), covert-acoustic channels can be used to communicate at data rates of hundreds of bits per second, without being detected by humans in the environment, and data rates of thousands of bits per second when nobody is around to hear the communication. Defence mechanisms to counter covert-acoustic channels are also proposed and evaluated, and, as a result, best practices for the designers of secure systems and secure facilities are presented. Additionally, the covertness of OOB-CCs, i.e., the amount of data that can be leaked before the channel is detected, is also determined for classical communication channels as well as for covert-acoustic channels.

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af, Klintberg Tord. "Air Gap Method : Air-Gaps in Building Construction to avoid Dampness & Mould." Doctoral thesis, KTH, Byggnadsteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102873.

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Judge, Andy. "Air Gap Elimination in Permanent Magnet Machines." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/123.

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In traditional Permanent Magnet Machines, such as electric motors and generators, power is transmitted by magnetic flux passing through an air gap, which has a very low magnetic permeability, limiting performance. However, reducing the air gap through traditional means carries risks in manufacturing, with tight tolerances and associated costs, and reliability, with thermal and dynamic effects requiring adequate clearance. Using a magnetically permeable, high dielectric strength material has the potential to improve magnetic performance, while at the same time offering performance advantages in heat transfer. Ferrofluids were studied as a method for improved permeability in the rotor / stator gap with a combined experimental and computational approach. Results show promise for the ferrofluid technique. An off-the-shelf motor system showed improved performance with ferrofluids vs. fluids of equivalent viscosity, and improved performance vs. an air gap at low RPM. New generator designs showed design dependent performance gains, although some potential for negative performance effects. A proof of concept generator was built and tested, with increased voltage vs. RPM predicted through virtual prototyping, and validated through experimentation, showing ~10% improvement on voltage vs. RPM at the <600 RPM range. More repeatable engineering tests demonstrated a ~30% increase in the voltage / RPM relationship for designs with an isolated stator chamber and a large stator - rotor gap. However, the effects were negative for a similar system with a small stator-rotor gap due to leakage flux effects. New contributions to the body of knowledge in this area include: Ã¢â‚¬Â¢ Application of the ferrofluid technique to axial flux designs. Ã¢â‚¬Â¢ Development of a virtual prototype, including variations in the fluid viscosity due to ferrohydrodynamic effects. Ã¢â‚¬Â¢ Consideration of negative effects of ferrofluid immersion, such as shear losses and increases in leakage flux. Ã¢â‚¬Â¢ Optimization of the design to eliminate increased viscous losses. The improved design has been designed, built, and tested, featuring isolation of the ferrofluid from the rotating region. This offers all of the performance gain of improved magnetic permeability, while minimizing the offsetting losses from increased shear effects.

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Richardson, Christopher. "Bridging the air gap : an information assurance perspective." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/355926/.

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The military has 5 domains of operations: Land, Sea, Air, Space and now Cyber. This 5th Domain is a heterogeneous network (of networks) of Communication and Information Systems (CIS) which were designed and accredited to meet Netcentric capability requirements; to be robust, secure and functional to the organisation’s needs. Those needs have changed. In the globalised economy and across the Battlespace, organisations now need to share information. Keeping our secrets, secret has been the watchwords of Information Security and the accreditation process; whilst sharing them securely across coalition, geo-physically dispersed networks has become the cyber security dilemma. The diversity of Advanced Persistent Threats, the contagion of Cyber Power and insecurity of coalition Interoperability has generated a plethora of vulnerabilities to the Cyber Domain. Necessity (fiscal and time-constraints) has created security gaps in deployed CIS architectures through their interconnections. This federated environment for superior decision making and shared situational awareness requires that Bridging the (new capability) Gaps needs to be more than just improving security (Confidentiality, Integrity and Availability) mechanisms to the technical system interfaces. The solution needs a new approach to creating and understanding a trusted,social-technical CIS environment and how these (sensitive) information assets should be managed, stored and transmitted. Information Assurance (IA) offers a cohesive architecture for coalition system (of systems) interoperability; the identification of strategies, skills and business processes required for effective information operations, management and exploitation. IA provides trusted, risk managed social-technical (Enterprise) infrastructures which are safe, resilient, dependable and secure. This thesis redefines IA architecture and creates models that recognise the integrated, complex issues within technical to organisational interoperability and the assurance that the right information is delivered to the right people at the right time in a trustworthy environment and identifies the need for IA practitioners and a necessary IA education for all Cyber Warriors.

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Narayan, Aditya. "Investigations on Air-cooled Air Gap Membrane Distillation and Radial Waveguides for Desalination." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78779.

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This thesis presents investigations on air-cooled air gap membrane distillation for desalination and the application of radial waveguides based on total internal reflection for solar thermal desalination. Using an air-cooled design for an air gap membrane distillation (AGMD) process may result in significantly lower energy requirements for desalination. Experiments were conducted on AGMD module to study the effect of air gap, support mesh conductivity and hydrophobicity, condensing surface hydrophobicity. A novel modular design was used in which modules could be used in a series configuration to increase the flux value for the distillate. The output from the series configuration was found to have about three times the production from a single pass water-cooled system with the same temperature difference between the saline and clear water streams. The results also indicated that the mesh conductivity had a favorable effect on the flux value whereas the hydrophobicity of the mesh had no significant effect. The hydrophobicity of the condensing surface was favorable on two accounts: first, it led to an increase in the flux of the distillate at temperatures below 60 °C and second, the temperature difference of the saline feed when it enters and leaves the module is lower which can lead to energy savings and higher yields when used in a series configuration. The second part of the thesis considers use of low-cost radial waveguides to collect and concentrate solar energy for use in thermal desalination processes. The optical-waveguide-based solar energy concentrators are based on total internal reflection and minimize/eliminate moving parts, tracking structures and cost. The use of optical waveguides for thermal desalination is explored using an analytical closed-form solution for the coupled optical and thermal transport of solar irradiation through a radial planar waveguide concentrator integrated with a central receiver. The analytical model is verified against and supported by computational optical ray tracing simulations. The effects of various design and operating parameters are systematically investigated on the system performance, which is quantified in terms of net thermal power delivered, aperture area required and collection efficiency. Design constraints like thermal stress, maximum continuous operation temperature and structural constraints have been considered to identify realistic waveguide configurations which are suitable for real world applications. The study provides realistic estimates for the performance achievable with radial planar waveguide concentrator-receiver configuration. In addition to this, a cost analysis has been conducted to determine the preferred design configurations that minimize the cost per unit area of the planar waveguide concentrator coupled to the receiver. Considering applications to thermal desalination which is a low temperature application, optimal design configuration of waveguide concentrator-receiver system is identified that result in the minimum levelized cost of power (LCOP).
Master of Science

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Lee, Long Hua. "Air-gap sacrificial materials by initiated chemical vapor deposition." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/44292.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007.
Includes bibliographical references (leaves 81-83).
P(neopentyl methacrylate-co-ethylene glycol dimethacrylate) copolymer, abbreviated as P(npMAco-EGDA), was selected as the potential air-gap sacrificial material among possible combination of twenty monomers and four crosslinkers. P(npMA-co-EGDA) was deposited onto substrates using initiated chemical vapor deposition (iCVD) technique. Spectroscopic data showed the effective incorporation of both components in the copolymer and the integrity of repeating units were retained. The onset temperature of decomposition of P(npMA-co-EGDA) copolymer could be tuned between 290-3500C by varying the composition of the copolymer. The removal rate of polymer was calculated based on interferometry signal-time curve. The activation energy was determined by fitting the rate of decomposition with logistic model and found to be 162.7+8kJ/mole, which was similar to published data. Flash pyrolysis gas chromatography mass spectroscopy analysis showed that the products of thermal decomposition are monomers, rearranged small molecules and low oligomers. The modulus and the hardness were in the range of 3.9 to 5.5 GPa and 0.38 to 0.75 GPa, respectively, and were higher than those of linear poly(methyl methacrylate) (PMMA). Air-gap structures were constructed in the following scheme: P(npMA-co-EGDA) was deposited on the substrate by iCVD, followed by spincasting PMMA electron beam resist and scanning electron beam lithography to implement patterns on the resist. Reactive ion etching (RIE) was then applied to simultaneously etch the PMMA resist and P(npMA-co-EGDA) sacrificial material away in a controlled manner, leaving the patterned sacrificial material on the substrate.
(cont.) A layer of porous silica was deposited to cover the substrate and the patterned sacrificial material by plasma-enhanced chemical vapor deposition (PECVD) at 2500C and the sample was thermally annealed to allow the decomposed fragments to diffuse through the overlayer of silica. Using the scheme described above, it was possible to construct air-gap structures with feature size of 200nm and feature height of 1 00nm.
by Long Hua Lee.
S.M.

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7

Delmont, Andres Emilio. "Shape distortion and air gap formation during continuous casting." Thesis, Sheffield Hallam University, 1985. http://shura.shu.ac.uk/19549/.

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A theoretical model has been developed which relates the build-up of stresses in the thin shell of steel solidifying in a continuously casting mould, to the shape distortion and the formation of an air gap. The work postulates that the behaviour of this shell can be analysed as that of a flexible structure formed by four elasto-perfectly plastic beams linked by rigid comers. This "box" represents the whole section of solidified shell at a given metallurgical height only if the section is totally detached from the mould. In general, it represents the detached corner portions alone. The rest of the shell is assumed to remain clamped against the mould wall by the metallostatic pressure. The thermal contraction of the neutral axis "filament" along the whole shell determines the amount of room which is available for the detached corner portion to distort, and thus also the size of the detached lengths of shell. The mechanical equilibrium of the structure is determined by the combined effect of temperature gradients and metallostatic pressure, by the rigidity condition imposed at the corner and by the flexural characteristics of the shell. The yield stress of the steel is assumed linearly dependent on temperature. The analysis of the shape distortion and air gap formation was initially informed by the observed behaviour of a partial physical analogue constructed from bi-metallic strips linked by rigid corners. Thermal moments were induced by immersing this analogue in a water bath at controlled temperatures, and distributed loads were imposed through a system of pulleys. The elastic behaviour of this physical analogue was predicted using basic beam theory. For the analysis of the deformation of a continuously cast structure, mathematical equations were derived which describe the overall moment and force equilibrium; the elastic and plastic stress distribution across the thickness of the shell; and the force and moment equilibrium within the cross-section of the shell. An equation was derived relating the curvature at any point along the shell to the moment at the corner of the structure. An iterative procedure was developed to determine the moment at the corner and a Runge-Kutta algorithm was incorporated to integrate the curvature equation. Further equations were derived which relate the deflection at the corner and the detached length on one side of the section, to the total length of the other side of the section. Recent high temperature studies of the mechanical behaviour of steels have been analysed in terms of the theoretical model developed. The model is able to predict the extent and thickness of the air gaps forming in the corner regions during the casting of billets and slabs and also provides explanation for the formation of both internal and external off-corner cracks. It also demonstrates the theoretical basis behind the practically observed relationship between casting speed and crack formation.

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Mauseth, Frank. "Charge accumulation in rod-plane air gap with covered rod." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1489.

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The focus of this work has been on hybrid insulation in inhomogeneous electric fields under lightning impulse voltage stress. The principal idea behind hybrid insulation is the intentional use of surface charges to re-distribute the electric field within an insulation system. This allows a significant part of the electric stress to be transferred from the dielectric weaker gas to the dielectric stronger solid insulation thus increasing the total electric strength of the insulation system.

The concept has been theoretically and experimentally addressed by means of a hemispheric rod covered with a layer of solid insulation. Discharge activity and surface charge accumulation have been studied in an air gap by measuring the voltage and discharge current and recording the discharge activity using a high-speed digital camera. New methods have been introduced and evaluated for the evaluation of surface charge measurements.

The experiments found that the increase in positive inception voltage was considerable compared to uncovered rods. This increase varied from 35% up to 100% depending on the electrode distance. The increase in breakdown strength is higher than the increase in inception voltage and dependent on the covered length of the rod. During the application of a lightning impulse, the discharge activity spreads upwards along the rod and out into the air gap. Positive discharges form numerous branches and bridge the air gap in most cases. Negative discharges are more diffuse, less light intensive and only form a few branches around the tip of the rod where the electric field is the strongest. Discharge activity along the insulating surface has been observed where the background field is lower than the critical electric field strength. Visible discharge activity is observed where the background field is higher than 2.3 kV/mm and 2.5 kV/mm for positive and negative impulses respectively.

During the application of lightning impulses, discharge activity starts in the air gap around the tip where the electric field is highest and spreads upwards along the rod. As expected, negative charges accumulate on the surface in the case of positive impulse voltage and vice versa. However, after more powerful discharges during negative impulse voltage application, surface charges of both polarities have been observed.

Accumulated surface charges decay exponentially with a time constant τ varying from micro-seconds to hours depending on the material properties of the solid insulation. The dominating relaxation mechanism is found to be conduction through the solid insulation.

Improved methods to calculate surface charges based on probe response for a 2D axial symmetric case have been developed and evaluated. The method that is best suited for this purpose is the λ-method with truncated singular value decomposition (TSVD) as regularization.

Surface charge calculations show that the accumulated surface charges for the used configuration typically have a maximum value of 0.6 to 1.5 µC/m² and 0.4 to 1 µC/m² after positive and negative impulses respectively. The surface charge density in the areas with the highest discharge activity is relatively uniform. Further upwards along the rod, the surface charge density is reduced relatively fast towards zero, and in some cases, it changes polarity before approaching zero.

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Alkhudhiri, Abdullah Ibrahim. "Treatment of saline solutions using air gap membrane distillation (AGMD)." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678440.

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Randhawa, Dev. "A synchronous generator monitoring system utilizing air-gap flux signals /." Title page, table of contents and abstract only, 1995. http://web4.library.adelaide.edu.au/theses/09ENS/09ensr191.pdf.

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Tsakok, Sebastian M. J. "Windage losses in the air gap of high speed generator." Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540682.

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Okubo, Hitoshi, Toshiaki Rokunohe, Tatsuro Kato, Norihito Yanagita, Fumihiro Endo, Naoki Hayakawa, Hiroki Kojima, and Takeshi Iwata. "POSITIVE STREAMER PROPAGATION AND BREAKDOWN CHARACTERISTICS IN NON-UNIFORM AIR GAP." IEEE, 2010. http://hdl.handle.net/2237/14456.

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Recanati, Maurice-Andre. "Design of an air gap armature for the MIT superconduting generator." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/34080.

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Palmby, William G. "Enhancement of Civil Reserve Air Fleet an alternative for bridging the airlift gap /." Maxwell AFB, Ala. : Air University Research Coordinator Office, 1998. http://www.au.af.mil/au/database/research/ay1995/saas/palmbywg.htm.

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Thesis (M.M.A.S.)--School of Advanced Airpower Studies, 1995.
Subject: This study examines whether a revival of the CRAF enhancement program is feasible and if it could be developed into a viable program for addressing AMC's airlift shortfall problem. Cover page date: June 1995. Vita. Includes bibliographical references.

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Stich, Andreas. "Development and electrical characterization of air gap structures for advanced metallization schemes." [S.l.] : [s.n.], 2007. http://mediatum2.ub.tum.de/doc/619302/document.pdf.

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Huang, Xianghui. "Diagnotics of Air Gap Eccentricity in Closed-Loop Drive-Connected Induction Motors." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6996.

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The trend toward ever-expanding variable speed induction motor applications results in the need for reliable condition monitoring and detection schemes for closed-loop motor-drive systems. This research focuses on the detection of air gap eccentricity in induction motors supplied by a vector-controlled drive. The majority of existing eccentricity detection techniques is based on monitoring fault harmonics in the stator current. This research analyzes the distribution of the eccentricity-related fault harmonics between the stator voltage and current, and points out that monitoring only the stator current is insufficient. When the motor is supplied by a vector-controlled drive, both voltage and current become modulated signals and contain fault harmonics. Either stator voltage or current can contain larger fault harmonics due to the influence of the drive controllers and the mechanical load. Therefore, a combination of monitoring both variables is necessary to ensure good detection reliability. Furthermore, with an AC drive, the motor speed and load will change widely, which changes fault harmonics too. A new detection scheme using an artificial neural network is proposed to incorporate the influence of changing operating conditions into the fault detection. This detection scheme is more reliable and cost efficient. In addition, a new off-line non-invasive eccentricity detection method is proposed by using the surge test. Simulation and experiments are conducted to validate the feasibilities of the proposed detection schemes.

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Thomas, Mark W. "Evaluation and optimization of axial air gap propulsion motors for naval vessels." Thesis, Monterey, California. Naval Postgraduate School, 1996. http://hdl.handle.net/10945/8347.

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Kazemi, Saeid. "Air gap response and potential deck impact analysis of floating offshore structures." Thesis, University of Newcastle Upon Tyne, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435637.

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Thomas, Mark W. (Mark Wayne). "Evaluation and optimization of axial air gap propulsion motors for naval vessels." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38167.

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Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1996, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.
Includes bibliographical references (leaves 89-90).
by Mark W. Thomas.
M.S.
Nav.E.

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Morales, Lucien L. "Visualization and measurement of filmwise and dropwise air gap membrane distillation at varied module inclination angle and gap spacer Orientation." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105688.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 36).
Improving efficiency is the main target for improving rapidly developing water desalination technologies such as air gap membrane distillation (AGMD). While the system is dominated by heat and mass transfer resistances in the air gap specifically, very little is known about the impact of variations in the air gap, including air gap spacers and module tilting. AGMD experiments were performed by varying inlet temperature, module inclination angle, and gap spacer to identify the effect on the permeate production rate of the system. While AGMD is potentially one of the most efficient types of membrane distillation, experimenting with the tilt angle of the module so as to rotate the membrane and condensation plate off the vertical, provides a method to alter the behavior of the film condensation layer and its associated thermal resistance. In this study, we confirm the previous work of Warsinger et al. (2014) through the added enhancement of visualization of condensation in the air gap by use of a clear and conductive sapphire condensation plate. Additional experiments were run observing the effect of changing the orientation of the mesh spacer holding the air gap in the vertical orientation. Numerical modeling is also conducted to understand and potentially verify the experimental results. As predicted, the results maintain that at near vertical and at non-extreme positive angles (<15° from the vertical), there is no significant difference in the permeate production output of the system due to tilting the module. At declined and extremely inclined tilt angles, the air gap in the module behaves as a "permeate gap", or a flooded system, resulting in the air gap saturated with liquid water. At negative tilt angles past 30°, it was found that condensate tends to fall on the membrane, causing thermal bridging, and as a result, significantly increasing the overall production of permeate condensate. It was also found that the orientation of the mesh spacer holding the air gap apart does not have a significant effect on the permeate production rate.
by Lucien L. Morales.
S.B.

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Sharp, Justin. "The structure and dynamics of Columbia Gorge gap flow revealed by high-resolution numerical modeling /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/10020.

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Spencer, Todd Joseph. "Air-gap transmission lines on printed circuit boards for chip-to-chip interconnections." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34754.

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Low-loss off-chip interconnects are required for energy-efficient communication in dense microprocessors. To meet these needs, air cavity parallel plate and microstrip lines with copper conductors were fabricated on an FR-4 epoxy-fiberglass substrate using conventional microelectronics manufacturing techniques. Copper transmission lines were separated by a composite dielectric of air and Avatrel 2000P and by a dielectric layer of air only. The composite dielectric lines were characterized to 10 GHz while the all air dielectric lines were characterized to 40 GHz. The transmission line structures showed loss as low 1.5 dB/cm at 40 GHz with an effective dielectric constant below 1.4. These novel structures show low loss in the dielectric due to the reduced relative permittivity and loss tangent introduced by the air cavity. Transmission line structures with a composite dielectric were built by coating the sacrificial polymer poly(propylene carbonate) (PPC) over a copper signal line, encapsulating with an overcoat polymer, electroplating a ground line, and decomposing PPC to form an air cavity. The signal and ground wires were separated by a layer of 15 µm of air and 20 µm of Avatrel 2000P. Air cavity formation reduced dielectric constant more than 30 percent and loss of less than 0.5 dB/cm was measured at 10 GHz. Residue from PPC decomposition was observed in the cavity of composite dielectric structures and the decomposition characteristics of PPC were evaluated to characterize the residue and understand its formation. Analysis of PPC decomposition based on molecular weight, molecular backbone structure, photoacid concentration and vapor pressure, casting solvent, and decomposition environment was performed using thermogravimetric analysis and extracting kinetic parameters. Novel interaction of copper and PPC was observed and characterized for the self-patterning of PPC on copper. Copper is dissolved from the surface during PPC spincoating and interacts with the polymer chains to improve stability. The improved thermal stability allows selective patterning of PPC on copper. Decomposition characteristics, residual metals analysis, and diffusion profile were analyzed. The unique interaction could simplify air-gap processing for transmission lines. Inorganic-organic hybrid polymers were characterized for use as overcoat materials. Curing characteristics of the monomers and mechanical properties of the polymer films were analyzed and compared with commercially available overcoat materials. The modulus and hardness of these polymers was too low for use as an air-gap overcoat, but may be valuable as a barrier layer for some applications. The knowledge gained from building transmission line structures with a composite dielectric, analyzing PPC decomposition, interaction with copper, and comparison of hybrid polymers with commercial overcoats was used to build air-gap structures with improved electrical design. The ground metal was separated from the signal only by air. The signal wire was supported from above using 60 µm of Avatrel 8000P as an overcoat. Structures showed loss of less than 1.5 dB/cm at 40 GHz, the lowest reported value for a fully encapsulated transmission line structure.

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DeLancey, Amanda L., Andrew J. Ramsey, and Caitlin E. Harris. "Green acquisition gap analysis of the United States Air Force Operational Contracting Organizations." Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/10591.

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MBA Professional Report
In this thesis, we explore the goals and requirements of green procurement in order to assess the Air Force's degree of success with incorporating the Defenses (DoD's) Green Procurement Program (GPP) into its procurement process. This thesis provides an outline of the federal policies and guidance regarding green procurement, including Executive Order 13514 (2009) and relevant parts of the Federal Acquisition Regulations. We examine the Air Force's progress towards a more environmentally friendly process, measured by the metrics set forth in the DoD GPP. To evaluate these metrics, we conducted an analysis to determine if the Air Force is implementing environmental considerations to the maximum extent practical. This analysis relied on the use of the Green Acquisition Gap Analysis (GAGA) model, which is a unique framework that we developed. The GAGA model fuses the personnel, platform, and protocol pillars of the Mandatory Pillars for Integrative Success (Yoder, 2010) framework with the Contract Management Process framework, which dissects the six segments of the contracting process: procurement planning, solicitation planning, the solicitation, source selection, contract administration, and contract closeout or termination (Rendon, 2007). Further, in order to document best practices for Air Force-wide dissemination, we identified the leading Air Force installations through our extensive research and collaboration with key leadership.

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Frackiewicz-Kaczmarek, Joanna. "Determination of the air gap thickness and the contact area under wearing conditions." Thesis, Mulhouse, 2013. http://www.theses.fr/2013MULH5151/document.

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Le transfert de masse et de chaleur dans les vêtements est un phénomène faisant appel àdifférents mécanismes physiques : les échanges de chaleurs sèches et les transferts de vapeur etde liquide. Ces mécanismes sont fortement influencés par les facteurs liés à la construction, laforme du vêtement par rapport à celle du corps et l’utilisation du vêtement. Ces facteurs peuventêtre optimisés en changeant la taille et la forme des différentes couches d’air emprisonnées entrela peau et les vêtements. La plupart des modèles mathématiques de vêtements font l’hypothèse que l’épaisseur d’air entrela peau et l’étoffe est uniforme, ou alors ils l’ignorent. La non-uniformité et de la non-linéaritédes transferts de chaleur et d’eau ne sont alors pas prises en compte. En effet, le processus detranspiration dépend non seulement de l’aire de contact et de l’épaisseur d’air emprisonnée entrela peau et le vêtement mais également de la région du corps. Nous proposons une méthode permettant de déterminer, avec une plus grande précision que lestechniques existantes, l’épaisseur d’air et l’aire de contact entre le corps et un vêtement à l’aided’une analyse avancée de scans 3D d’un mannequin homme nu et habillé. L’effet du tauxd’humidité sur l’aire de contact et l’épaisseur du film d’air a été étudié en fonction de la zone ducorps et ceci pour différentes tailles, structures de l’étoffe et fibres. Cette méthode contribue àévaluer de façon plus réaliste les échanges de masse et de chaleur au travers de plusieurs couchesde vêtements et ainsi de fournir des données d’entrée précises aux modèles pour la conception devêtements avec prise en compte du confort et de l’ergonomie
The heat and mass transfer within the clothing system is a composition of a number of physicalprocesses, such as: dry heat and vapour and liquid water transfer. Factors associated with theconstruction and use of the garment, such as body posture and movement, and clothing fitinfluence these processes significantly. This is achieved mainly by changing the size and theshape of the different layers of air trapped between the skin and clothing. Most existing mathematical clothing models assume uniform air gap between the body and fabric layers or ignore it. However, this approach disregards the non-uniform and non-linear heat,vapour and liquid water transfer, which depend on presence of contact between surfaces and onthe shape of the air layers trapped within clothing and the body regions which are not equivalentin terms of sweating process. In this study, we propose a method to accurately determine the air gap thickness and the contactarea between clothing and the human body through an advanced analysis of 3D body scans of thenude and dressed body of a male manikin. This method allowed more accurate measurement ofthe air gap thickness and the contact area than other existing methods. Additionally, in two casestudies the effect of garment design and moisture gain in fabric combined with effects of bodypart, garment type and its overall and regional fit, fabric structure and fibre type were determined.Consequently, this method will contribute to a more realistic evaluation of heat and massexchange rates through clothing systems and provide more accurate input for ergonomic andcomfort design of clothing

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Wang, Yiren. "Modelling and characterisation of losses in nanocrystalline cores." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/modelling-and-characterisation-of-losses-in-nanocrystalline-cores(eddd2c60-7322-4665-9176-b45e53621285).html.

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Increasing the power density of the DC-DC converters requires the size and weight of the magnetic components, such as inductors and transformers, to be reduced. In this thesis, the losses in nanocrystalline inductor cores are characterised and analysed, including the traditional core loss and the gap loss caused by the air gap fringing flux. The loss calculations will form a basis for the design and optimisation of high power inductors for DC-DC converters for EV applications. This thesis first characterises experimentally the core losses in four nanocrystalline cores over a range of operating conditions that are representative of those encontered in typical high power converter applications, including non-sinusoidal waveforms and DC bias conditions. The core losses are assessed by the measured B-H loops and are characterised as a function of DC flux density, showing that for a fixed AC induction level, the losses can vary by almost an order of magnitude as the DC bias increases and the duty ratio moves away from 0.5. The results provide a more complete picture of the core loss variations with both DC and AC magnetisations than is available in manufactures’ data sheets. An electromagnetic finite element (FE) model is used to examine the gap loss that occurs in finely laminated nanocrystalline cores under high frequency operation. The loss is significant in the design example, contributing to almost half of the total inductor loss, and the gap loss is highly concentrated in the region of the air gap. The dependence of the gap loss on key inductor design parameters and operating condtions is also explored. An empirical equation is derived to provide a design-oriented basis for estimating gap losses. Thermal finite element analysis is used to estimate the temperature rise and identify the hot spot in a nanocrystalline inductor encapsulated in an alumimium case. The temperature distribution in the core largely corresponds to the non-uniform distribution of the gap loss. The thermal FEA can also be used to evaluate different thermal management methods to optimise the design for a more compact component. The FE modelling of gap loss and the thermal predictions are validated experimentally on a foil-wound Finemet inductor, showing good agreement between the predictions and measurements under various operating conditions.

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26

Kron, Jenny. "Air gap formation and hot tearing in solidification processing of Al- and Cu-base alloys." Doctoral thesis, KTH, Casting of Metals, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3714.

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Shrinkage in a solidifying metal has been studiedexperimentally as well as theoretically. The main focus hasbeen to examine the mechanisms causing an air gap to formbetween a casting and a mould, and hot crack formation to occurin a solidifying metal.

¨The formation of an air gap has been experimentallystudied during solidification of Al- and Cu-based alloys in acylindrical mould. The displacements of the casting and themould causing an air gap have been measured duringsolidification and cooling of the casting. The temperaturedistribution was measured simultaneously. Mathematicalmodelling has been performed to increase the understanding ofthe solidification process and the strains formed in thesolidifying metal contributing to the formation of an air gapbetween casting and mould. Most of the work was dedicated todevelop a new model to describe the strain duringsolidification, but traditional theory was used for themodelling work as well.

The model suggested in this work includes non-equilibriumeffects on the solidification process and the shrinkage. Theformation and condensation of lattice defects formed in thesolid phase during solidification and its effect on thesolidification process as well as on the material shrinkageresulting in air gap formation was considered. The results fromthe modelling work show good agreement with the experimentalresults. The conclusion is that it is important to includethese non-equilibrium effects in modelling of shrinkage duringsolidification.

The same conclusion was drawn from results of experimentalwork with high temperature tensile testing of in situsolidified samples and the development of a new theory for hotcrack formation. It was found that a super saturation oflattice defects formed during the solidification processenhances the nucleation and growth of hot cracks duringcooling.

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27

Cameron, James R. "Vibration and current monitoring for on-line detection of air-gap eccentricity in induction motors." Thesis, Robert Gordon University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328784.

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Novak, D., and A. Moshenskyy. "Wearable system for monitoring of internal microclimate changes in the air gap between cloth layers." Thesis, Київський національний університет технологій та дизайну, 2019. https://er.knutd.edu.ua/handle/123456789/14605.

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29

Bahceci, Mesut. "Simulation of an Electrical Machine : with superconducting magnetic bearings." Thesis, Uppsala universitet, Elektricitetslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-242127.

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This master thesis investigates if there is an induction motor configuration that can be used with a flywheel energy storage system, that uses passve superconducting magnetic bearings (SMBs). The configurations should be able to be designed with induction motor building blocks that are commercially available. The method used to investigate this was simulations of different induction motor configurations in the finite element analysis software COMSOL. The simulations show that when larger air-gaps than that of a commercial IM unit are used it is possible to use SMBs in the IM. SMBs have the advantage of having zero resistance which makes it possible to store energy without resistance losses. However it was found that by using and IM with SMBs the generated power would be lower than that of a commercial unit.

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Mularcik, Bradley S. "Virtual Moving Air Gap for the Speed Range Improvement of a Dual Stator Axial Flux Motor." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1340404856.

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31

Sharifi, Masoud. "Accuracy criteria and finite element study of a highly saturated magnetic device with a large air-gap." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0009/NQ49878.pdf.

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32

Hailom, Yosef Futsum. "Solidification of iron and nickel base alloys and its relation to hot crack and air gap formation /." Stockholm : Casting of Metals, Royal Institute of Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3856.

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33

Kallel, Bilel. "Design of Inductive Power Transmission System for Low Power Application with Movable Receiver and Large Air Gap." Universitätsverlag Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A32975.

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Inductive power transmission is very useful, not only for systems where energy transfer should take place in hazardous, humid and wet areas, but also for mobile and very small systems. It finds today a widespread use in several fields, such as industry, automotive, medicine and smart buildings. For a good efficiency and a high-power transmission, the sending and the receiving coils should be perfectly aligned and close to each other. A misalignment between the sender and the receiver becomes unavoidable especially for systems with movable parts. This thesis aims to improve the transmitted power, the mutual inductance, the power at the load, and consequently the power transmission efficiency in case of lateral misalignment between the sending and receiving coils and at large coil-to-coil distance. For this purpose, we adopt a multi input single output (MISO) coil system able to orientate the issued magnetic field to the receiving coil by powering the neighbouring sending coils of the active ones with a weak current in the opposite direction. Furthermore, an analytical model of the used coils and an accurate three-dimensional model of the system have been developed to calculate the induced voltage, the induced current, and the equivalent mutual inductance. Both simulation and experimental results prove that the proposed multi-coil inductive system having an hexagonal arrangement and the sending coils, which have the half diameter of the receiving coil, is able to improve significantly the transmitted power in case of lateral misalignment and big air gap. The novel MISO system reaches better efficiency beginning with an air gap of 50% of the sending coil diameter, and a misalignment of 28% of the sending coil diameter. It reaches the double of the transmitted power of the conventional two-coil inductive system at 50 mm air gap (corresponding to 166% of the sending coil diameter) and at 10 mm lateral misalignment (corresponding to 33% of the sending coil diameter). In order to improve the equivalent mutual inductance between the primary and secondary sides and to avoid energy losses, we propose a receiver detection method using the sending coils themselves as detectors. Thereby, only the sending coils, under the receiver, are activated and the others remain switched off. For that, the peak of the AC current of the sending coils, is measured and then compared to a detection threshold. The excitation strategy of the active sending coils is optimized corresponding to the receiving coil position. The novel excitation strategy increases the mutual inductance by 85% and the induced voltage by 13% at perfect alignment and by 30% and 10% respectively at 10 mm lateral misalignment, in comparison to the MISO system without a receiver detector and coil-excitation strategy. In order to increase the transmitted power by resonance, different system topologies have been investigated, such as series-series SS, series-parallel SP, parallel-series PS, and parallel-parallel PP topologies for different levels of load impedance. The results show that a multi-coil inductive system with parallel-parallel PP topology realizes a higher transmitted power than the other topologies for both high and low load impedance values. The proposed multi-coil inductive system is suitable for low-power systems, such as wireless sensors and biomedical implants, but can be also applied to higher range of power at a flexible position of the receiver.
Die induktive Energieübertragung ist interessant, nicht nur für Systeme, bei denen die Energieübertragung in rauen, feuchten und nassen Bereichen erfolgen soll, sondern auch für mobile und sehr kleine Systeme. Diese Art von Energieübertragung findet heute eine breite Anwendung in verschiedenen Bereichen, wie z.B. Industrie, Automobil, Medizin und intelligente Gebäude. Um eine gute Effizienz und eine hohe Energieübertragungsleistung zu realisieren, sollten die Sende- und Empfangsspulen perfekt ausgerichtet und nahe beieinander sein. Insbesondere bei Systemen mit beweglichen Teilen ist jedoch eine Fehlausrichtung zwischen Sender und Empfänger unvermeidlich. Diese Arbeit zielt darauf ab, die übertragene Leistung, die gegenseitige Induktivität, die Leistung an der Last und damit den Wirkungsgrad der Leistungsübertragung im Falle einer seitlichen Fehlausrichtung zwischen Sende- und Empfangsspule und bei großem Abstand von Spule zu Spule zu verbessern. Zu diesem Zweck wird ein Multi-Input Single-Output (MISO)-Spulensystem vorgeschlagen, das in der Lage ist, das ausgegebene Magnetfeld auf die Empfangsspule auszurichten, indem die benachbarten Spulen der aktiven Sendespulen mit einem schwachen Strom in der entgegengesetzten Richtung versorgt wird. Darüber hinaus wurde ein analytisches Modell für die verwendeten Spulen und ein genaues dreidimensionales Modell für das System entwickelt, um die induzierte Spannung, den induzierten Strom und die äquivalente gegenseitige Induktivität zu berechnen. Sowohl die Simulation als auch die experimentellen Ergebnisse belegen, dass das vorgeschlagene induktive Mehrfachspulensystem mit hexagonaler Anordnung und die Sendespulen, die den halben Durchmesser der Empfangsspule haben, in der Lage sind, die Sendeleistung bei lateraler Fehlausrichtung und großem Luftspalt deutlich zu verbessern. Das neuartige MISO-System erreicht einen besseren Wirkungsgrad, beginnend mit einem Luftspalt von 50% des Sendespulendurchmessers und einer Fehlausrichtung von 28% des Sendespulendurchmessers. Sie erreicht bei 50 mm Luftspalt (entspricht 166% des Sendespulendurchmessers) und bei 10 mm seitlichem Versatz (entspricht 33% des Sendespulendurchmessers) das Doppelte der Sendeleistung des herkömmlichen Zwei-Spulen-Induktivsystems. Um die äquivalente gegenseitige Induktivität zwischen Primär- und Sekundärseite zu verbessern und Energieverluste zu vermeiden, schlagen wir ein Verfahren zur Detektion des Empfängers vor, bei dem die Sendespulen selbst als Detektoren verwendet werden. Dabei werden nur die Sendespulen unter dem Empfänger aktiviert und die anderen bleiben ausgeschaltet. Dazu wird der Scheitelwert des Wechselstroms der Sendespulen gemessen und mit einem vorgegebenem Schwellenwert verglichen. Die Anregungsstrategie der aktiven Spulen wird entsprechend der Position der Empfangsspule optimiert. Die neuartige Anregungsstrategie erhöht die gegenseitige Induktivität um 85% und die induzierte Spannung um 13% bei perfekter Ausrichtung und um 30% bzw. 10% bei 10 mm seitlichem Versatz, im Vergleich zum MISO-System ohne Empfängerdetektor und Spulenanregungsstrategie. Um die übertragene Leistung durch Resonanz zu erhöhen, wurden verschiedene Systemtopologien untersucht, wie z.B. Serien-SS, Serien-Parallel-SP, Parallel-Series-PS und Parallel-Parallel-PP-Topologien für verschiedene Stufen der Lastimpedanz. Die Ergebnisse zeigen, dass ein MISO System mit parallel-paralleler PP-Topologie eine höhere Sendeleistung realisiert als die anderen Topologien für hohe und niedrige Last-Impedanzen. Das vorgeschlagene induktive Mehrspulensystem eignet sich für Systeme mit geringer Leistung, wie drahtlose Sensoren und biomedizinische Implantate, kann aber auch flexibler Position des Empfängers in einen höheren Leistungsbereich angewendet werden.

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Yang, Linda, and Robert Liao. "Water Purification : Research on the Energy Supply of Air Gap Membrane Distillation for Access to Clean Water." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-282905.

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Water stress is an ongoing problem in many places in the world, while the demand for clean and safe freshwater is growing due to the increasing population. In many developing countries, water supplies often are contaminated with arsenic, fluoride, etc. Therefore, it is important to realize that water scarcity and contamination issues concern only one sector but many. HVR Water Purification AB is developing a water purification prototype – ELIXIR 500 - using the air gap membrane technology and is implemented in Odisha, India, aiming to supply with 200 litre water daily. This thesis aims to estimate future energy sources to supply this prototype and explore the possibilities of using only renewable energy resources from technical, economic, and environmental perspectives. These are achieved by firstly identifying the energy possibilities in Odisha, India, and then calculating the feasibility of each solution chosen and finally analyzing the results. Among the energy sources, which are power grid, wind and solar power, diesel generator and solar-diesel hybrid system. It is found that the energy source to the prototype supplied by the power grid is 0.057 USD per litre water, which is the cheapest option. However, it is not feasible due to the lack of electrification from the local network. Meanwhile, the solar-diesel hybridized energy system is the most economical option if renewable energy sources are integrated with 0.11 USD per litre water.
Vattenstress ett pågående problem på många ställen i världen medan efterfrågan på rent och säkert dricksvatten växer på grund av den ökande befolkningen. I många utvecklingsländer är vattenförsörjningen ofta förorenade med arsenik, fluor osv. Det är därför viktigt att inse att vattenbrist och föroreningar inte bara rör en sektor utan många. HVR Water Purification AB utvecklade en prototyp för vattenrening - ELIXIR 500 - med hjälp av luftspaltmembrantekniken (eng: air gap membrane distillation och implementeras redan i Odisha, Indien, med målet att förse 200 liter rent vatten dagligt. Denna avhandling syftar till att uppskatta de framtida energikällorna för att tillhandahålla denna prototyp och utforska möjligheterna att endast använda förnybara energikällor ur tekniska, ekonomiska och miljömässiga perspektiv. Dessa uppnås genom att först identifiera de olika energimöjligheter i Odisha, Indien, följt av beräkningar om utförbarhet för varje vald lösning och slutligen en analys av resultaten. Bland energikällorna elnät, vind, sol, diesel generator och sol-diesel hybrid system har visat sig att energikällan till prototypen som levereras av elnätet som kostar 0.057 USD per liter vatten som det billigaste alternativet, men det är inte möjligt på grund av bristen på elektrifiering från det lokala elnätet. Å andra sidan är det hybridiserade energiskombinationen med solkrafts och diesel det billigaste alternativet om förnybara energikällor ska integreras, resultatet visade att vara 0.11 USD per liter vatten.

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Mert, Emel. "Effect of air gap thickness and contact area on heat transfer through garments in real life situation." Thesis, Mulhouse, 2016. http://www.theses.fr/2016MULH9978.

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Le corps humain et les vêtements sont toujours en interaction directe avec l’environnement, le corps devant maintenir sa température à environ 37°C. Les transferts de chaleur sont affectés non seulement par les propriétés de l’étoffe constitutives du vêtement, mais également par l’épaisseur de la couche d’air entre le corps et le vêtement. Les propriétés thermiques de la couche d’air dépendent de son étendue, influencée par les courbures du corps humain, des propriétés mécaniques de l’étoffe et de la forme du vêtement. Il est donc nécessaire de déterminer la forme 3D du corps et la répartition, l’étendue et l’épaisseur de la couche d’air ainsi que les zones de contact entre la peau et le vêtement dans des conditions posturales de la vie courante. Dans la présente étude, l’influence thermique de couches d’air homogènes (épaisseur constante) et hétérogènes (épaisseur variable) a été montrée. De plus, la distribution des couches d’air et de l’aire de contact réelle a été analysée minutieusement. L’influence des conditions posturales (à l’aide d’un mannequin) et du mouvement (à l’aide d’un logiciel de simulation de mouvement) a été étudiée dans différents cas. Une méthode de post-traitement des données provenant du logiciel de simulation 3D de mouvement a alors été mise au point. Les résultats montrent que le niveau de confort peut être ajusté en sélectionnant l’étoffe et la forme du vêtement et que cela dépend de la région du corps. La connaissance issue de cette étude sera directement utilisée en modélisation des transferts de chaleur au travers des vêtements et contribue à l’amélioration de la conception des vêtements pour la protection ou la pratique sportive
In real life, human body and clothing are always in direct interaction with environment, where human body attempts to keep its core temperature constant at around 37 °C by physiological thermoregulatory processes. The heat transfer from the wearer’s body to the environment is affected not only by the fabric properties but also by the presence of air layers and the contact between body and garment. The thermal properties of air layer are related to its size, which in turn, depends on the form of the wearer’s body, mechanical properties of fabric and garment design. Therefore, it is necessary to determine the three dimensional (3D) map and the quantitatively determination of air layers and contact area on the garment in real life situations, such as for various body postures and movement. In the present study, a comparison of the thermal effect of the heterogeneous and homogeneous air layers was sought. Additionally, the distribution of air layers and the contact area for lower body garments were analysed systematically. The effect of various body posture and movement on sought parameters was investigated. Moreover, new method was introduced to post-process the sought parameters for the ready output from 3D simulation software. Consequently, the results of this study indicated that the comfort level of the human body can be adjusted by selection of fabric type and the design of ease allowances in the garment depending on the body region and given purpose. The knowledge gained in this study will be directly used in modelling of the dry and latent heat transfer through garment and contribute to the improvement of clothing design for protective and active sport garments

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af, Klintberg Tord. "Heated air gaps : a possibility to dry out dampness from building constructions." Licentiate thesis, KTH, Civil and Architectural Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9490.

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The air gap method is a modification of the common way of building indoor walls and floors. The aim of the method is to make a construction, less fragile to water damage, with air gaps where moisture can be removed with a thermally driven air flow, caused by a heating cable. The thesis includes a number of experimental studies of this method.

Temperature and convective air flow in a vertical air gap was studied and it was noted how air flow increased with raised power of the heating cable. The air flow for one meter of wall varied between 50 m3/day (13 air changes per hour) and 140 m3/day (36 air changes per hour). The lower value was caused by a temperature difference in the range 0.2-0.3 oC. Without heating no air flow was found.

In studies of moisture and RH in wet “slab on ground” constructions, it was noted how the slab in the room with the air gap method dried to a much higher extent than the slab in the room built in an ordinary way. It was also noted that moisture was transported from the air gap in the floor and up through the air gap in the wall. In the room with the air gap construction, the RH values beneath the floor was at a lower level (and below 75 % RH) than the RH values beneath the floor of conventional construction. Mould does not grow below 75 % RH.

In the study of a flooded intermediate floor it was noted how the thermally driven convective air flow evidently speeded up drying of the construction. Mould growth was only noted in the case where the heating cables were turned off.

Spaltmetoden är en modifiering av det reguljära sättet av att bygga innerväggar och bjälklag. Syftet med metoden är att skapa en byggnadskonstruktion som är mindre skör med avseende på fuktskador. Detta görs med spalter där fukt kan avlägsnas genom ett termiskt drivet luftflöde som orsakas av en värmekabel. Denna avhandling innehåller ett antal experimentella studier på metoden. Spaltmetoden har studerats med avseende på 1. Samband mellan temperatur och luftflöde, 2. Uttorkning och RF nivåer i golvkonstruktioner samt 3. Översvämning av ett mellanbjälklag

1. Samband mellan temperatur och luftflöde

Temperatur och konvektivt luftflöde har studerats i en vertikal spalt och resultatet visar att luftflödet ökar med ökad effekt hos värmekabeln. Luftflödet i en vägg med en meters bredd varierade mellan 50 kubikmeter/dag (13 luftväxlingar per timme) och 140 kubikmeter/dag (36 luftväxlingar per timme). Det lägre flödet orsakades av en temperaturskillnad på 0,2-0,3 oC mellan luftspalt och rum. När värmekabeln var avstängd så registrerades inget luftflöde.

2. Uttorkning och RF nivåer i golvkonstruktioner ovan betongplatta

Detta experiment visade att fukt har transporterats från spalten i golvet genom spalten i väggen ut i rumsluften. I spaltkonstruktion var RF inuti golvkonstruktionen lägre (och understeg 75 % RF), jämfört med den konventionella konstruktionen, (mögel växer inte under 75 % RF). Det har också registrerats att betongplattan som hörde till spaltmetoden torkade ut snabbare än betongplattan som var inbyggd i ett gängse rum.

3. Översvämning av ett mellanbjälklag

I studien där ett mellanbjälklag blev översvämmat noterades att spaltmetoden förkortade torktiden från 21 dagar till 13 vid den fuktigaste mätpunkten. Mögelväxt noterades endast då värmekabeln hade varit frånslagen.

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Zucchini, Elena. "Students’ holiday air travel behaviors: a flyer’s dilemma." Thesis, Uppsala universitet, Institutionen för samhällsbyggnad och industriell teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444564.

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Holiday air travel behaviors are nowadays a significant issue in relation to climate change and sustainable tourism. Indeed, transportation, and especially air transportation, have a significant role in climate change. Hence, it is important that the tourism industry includes the transportation sector when developing solutions for sustainable tourism. As students are the future main target group of this industry, it is important to understand the reasons behind their choices. Until now, travel behaviors have been explained using single and specific theories, which did not include many factors explaining holiday air travel decisions. In this study, this concern is addressed by combining two theories in relation to behavior formation - the theory of planned behavior and the value-belief-norm theory - in order to understand all motivations and barriers behind students’ holiday air travel behaviors. The analysis of the findings shows that many internal and external factors affect students decisions in regards to flying during holidays, including values, beliefs, social and personal norms, as well as accessibility, country of origin, price, time, distance, and social influence. However, the analysis of the results also demonstrates two gaps between attitudes and behaviors within the student community, which link to the cognitive dissonance theory: an awareness-attitude behavior gap and a contextual gap. The paper argues that while the theory of planned behavior and the value-belief-norm theory can be used simultaneously in order to analyze decisions regarding holiday air transportation, they are not sufficient as these two gaps emerged. The study concludes suggesting destination developers and national governments to take into account the present factors behind students’ decisions in order to develop sustainable destinations.

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Pirouzfar, Pedram. "Methods for verification of ultra-pure water with air gap membrane distillation : Focusing on applications in the semiconductor industry." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-80018.

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In the semiconductor industry, the purification process of the silicon wafers is of a great importance. If water of sufficient quality is not used, the silicon wafer surface runs a risk of being destroyed by particles and bacteria sticking to its surface. Semiconductors cannot be manufactured on the destroyed surfaces and to achieve the highest efficiency of the circuits, water with high purity is required for the purification process. The silicon wafers produced by the manufacturer have an oxide layer on them as a protective layer. This oxide layer needs to be cleaned off before it can be used for the manufacture of semiconductors. The oxide layer is removed by applying 5% hydrogen fluoride (HF) to the surface which is afterwards cleaned away with water. It is mainly within this part of the purification process that particles and bacteria get stuck on the surface of the silicon wafer. At present, water of poor quality is used which is unable to dilute and purify the mixture that becomes with hydrogen fluoride and the oxide layer. As development is constantly advancing and the line width of the circuits becomes narrower and smaller, water with almost no particles is needed to clean these small areas. The particle size of the water must not exceed 20 nm in order to effectively clean the silicon wafers and preferably the particle size should not exceed 10 nm. In the present study, an air gap membrane distillation module was investigated for the purpose of verifying the purity of the water where spherical spheres of 20 nm diameter were added into the purified water and examined in a dynamic light scattering (DLS). Because ultra-pure water (UPW) is a very aggressive water, storage is a problem. Four different container materials ability to store UPW with maintained purity were studied; white borosilicate ice cream, brown borosilicate ice cream, ethylene chlorotrifluoroethylene (ECTFE) and polyvinylidene fluoride (PVDF). Experiments were also done to further verify the purity of the water by adding ultra-pure water on a silicon wafer and allowing it to dry to study the dry spots. The dry spots were studied in an SEM to see if the water left any particles behind on the surface. The same experiment was also done with tap water and distilled water which was dripped on a silicon wafer and dried. These dry spots were examined in a scanning electron microscope (SEM). To investigate how effectively ultra-pure water cleans a silicon wafer, an amount of 5% hydrogen fluoride on a silicon wafer was added and rinsed with ultra-pure water and tap water respectively. The same experiment was also done with tap water for comparison. These silicon wafers were studied in an SEM to see if any particles were left on its surface from the respective water. An initial methodology was also done when 5% hydrogen fluoride was diluted with ultra-pure water and tap water to compare the amount of respective water it used to dilute this acid. In the present study, simulations were made on the air gap membrane distillation module in COMSOL where four different geometries were simulated with the aim to see how the temperature profile on the hot and cold side changed as the geometry and area of the membranes changed. The purity of the water produced with the air gap membrane distillation were verified with DLS and the particle size did not exceed 20 nm. Further experiments showed that with UPW, there were no dry spots on the surface of the silicon wafer and no particles could be seen when the silicon wafer was examined in an SEM. When the tap water was dropped on the silicon wafer and dried, one could clearly see the drying spots. When the silicon wafer was examined in an SEM, there were many particles left on the surface. The distilled water left no drying stains on the surface but on the other hand, it was able to see particles on the surface examined when in an SEM. When 5% hydrogen fluoride had been dropped on the surface and washed away with UPW, no particles could be detected when examined in an SEM. However, particles were found when the same amount of hydrogen fluoride was rinsed off with tap water. When 5% hydrogen fluoride was diluted to a neutral pH of 6-7, about 200 ml of UPW was used as separated from tap water where it went to the quadruple to dilute the same amount of hydrogen fluoride. This showed the purity of the ultra-pure water compared to tap water. For the simulations it was possible to see how the temperature profile changed with the area. With a large area, the temperature profile on the hot and cold side became very poor. The temperature on the hot side dropped a lot and on the cold side it increased a lot. The largest area simulated was 255x255 mm. With a smaller area, a more even temperature profile was obtained. The area that gave the best temperature profile was 180x100 mm, which was the smallest area investigated. In contrast, the diffusion area becomes smaller as the area decreases, leading to a reduced production of ultra-pure water. This study is close to research and is about developing new technology and modifying/improving existing technology.

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Chen, Chien-Chih, and 陳建智. "Desalination by air gap membrane distillation." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/94n57h.

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碩士
國立臺北科技大學
化學工程研究所
100
The membrane distillation (MD) has recently been developed to become an important technology in desalination become it owns some advantages，such as：simple design with modularity，high level of interface area and low installation and operating costs. Membrane distillation uses the driving forces coming from and the difference of vapor pressure across the membrane and the temperature difference between the hot sea water and the cold water，which is the difference between MD and other membrane technology for separation. In MD technology，the water vapor will pass a porous hydrophobic membrane and then the water comes out after the vapor goes through the cold end. In this study，Teflon film PTFE (Polytetrafluoroethene) air gap membrane was used in the system to distill the simulated sea water，investigate the influence of the fluid flow pattern on the flux of permeation and estimate the theoretical flux of permeation. The water temperature at the cold end was set at 25℃ and the temperature difference between the hot and cold fluid was changed to enhance the efficiency of MD and the production of pure water. Based on the air gap membrane distillation model for desalination，there were four key factors：(a).the hot fluid inlet temperature (b). the volume of fluid flow (c). the size of membrane pores (d). sodium chloride (NaCl) concentration. Which would affect the water production and NaCl removal，to be discussed in this study. The experimental results showed that both of the NaCl removal rate and the water production were be increased with the hot fluid inlet temperature and the volume of fluid flow. The size of membrane pores did not affect the removal of NaCl that much but it would affect the water production rate.

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40

Lin, Guei-ru, and 林桂如. "Air-Gap Long Period Fiber Gratings." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/33657734422594563207.

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碩士
逢甲大學
電機工程所
97
The content of this thesis is to achieve a humidity sensors based on air-gap long-period grating fibers which are fabricated by the fiber side-polishing, micro-lithography and hydro-fluoric acid fiber-etching techniques. Further, this thesis reported that the fabrication techniques are applied in photonic crystal fibers for fabricating air-gap long-period grating fiber, the etching process, temperature changes and the refractive index characteristics measurement. For an LPG, the core modes are coupled to the cladding modes, in which the resonant wavelength locations depend on the grating period and index modulation. The index modulation is composed of the periodically alternating distribution of the fiber-core index and air. When the core index or cladding index is changed, the resonant wavelengths are shifted and the energy losses of the resonant wavelengths are also varied. For sensing humidity, an air-gap long-period grating fiber sensor based on a single-mode fiber coated by the calcium-chloride thin-film is fabricated. The experimental results demonstrated that the shift of the resonant wavelength is 51 nm in the humidity range from 55% to 95%, which corresponded to the sensitivity of abut 1.36 nm/1%RH. Moreover, the air-gap long-period grating in photonic crystal fibers can be used for sensing different concentrations of salt solution. The experimental results show the maximum sensitivity of 736.4 nm /unit index to be obtained. The sensor is less sensitive to the temperature variation. This novel sensing head can provide a simply high-sensitivity fiber sensor for a wide range of detecting applications.

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41

Yang, Chin-Ming, and 楊敬明. "Development of Automatic Air Gap Adjusting Mechanism for Innovative Air Floating Stage." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/87366261533799182065.

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碩士
國立交通大學
工學院精密與自動化工程學程
100
The objective of the thesis is to design an air gap self-adjusting mechanism by applying hydrostatic type air bearing theory and force function. The thesis proposes an integration control unit including the proportional pressure valve and linear optical scale sensor (LVDT) as real time air gap height detector and compensator respectively. This gap height pneumatic control unit can control the air bearing inlet pressure for maintaining the defined air gap height to afford required plane levelness. The experimental model of air gap self -adjusting mechanism of the air gap floating stage has also been designed based on the hydrostatic theory and dynamic characteristics analysis using ADAMS. The investigation results derived both from theoretical and experimental process show that, 1μm levelness accuracy and 400ms system signal response time can be achieved by using the air bearing inlet pressure control technology to keep it in the required status of air gap height. The proposed innovative self-adjusting mechanism demonstrates a new alternative approach of error compensation method for the application of new designed precision machinery and measuring equipment without the requirement of complex configuration and control system architecture. The pressure and control model of the proposed air bearing can be a reference in the similar application such as thrust hydrostatic bearing design.

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42

Lin, Ming-Chang, and 林明昌. "Air-Gap Cu Damascene Structure by Removing Sacrificial Layer." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/42222377387032589371.

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碩士
國立清華大學
電子工程研究所
95
Two objectives are involved in the thesis. First, the fabrication of air-gap Cu damascene structure integrated with sacrificial layer HSQ, diffusion barrier TaN, adhesion layer Ta, electrochemical plating (ECP) of copper, and chemical mechanical polish (CMP) is demonstrated. Second, the air-gap formation by HSQ removal through a dielectric cap using MEMS technique is investigated, and the resistivity of copper lines is also studied. HSQ with MIBK at ratio 2:1 was spun on etch stop layer SiNx. The HSQ film pre-baked at 350℃ for 3 minutes was a good sacrificial layer which could easily and quickly be removed from the interface with other dielectric materials by BOE solution treatment. 100�� Ta and 100�� TaN served as the adhesion and diffusion barrier layer, respectively. After trench filling by copper ECP, several CMP parameters were applied to remove unnecessary Cu/Ta/TaN without damaging the samples, and Cu damascene structure was done. Then 4000�� SiNx deposited by PECVD was used as the dielectric cap. Etching windows with 1.5x line width / 2.5μm (window width / window length) on SiNx were formed by RIE with CF4 etchant and separated with 10μm along Cu damascene lines. The air-gap Cu damascene structure will be fabricated by BOE etching process. High resolution OM and SEM revealed the structure. The resistivity of Cu lines was measured by HP 4156A with a probe station and Conductive AFM. The measurement results of the two approaches were discussed in the thesis.

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43

Hsu, Chih-Kai, and 許智凱. "Electromigration Study on Sn capped Air-gap Cu Damascenes Structure." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/76074042031188978018.

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碩士
國立清華大學
電子工程研究所
94
Abstract The fabrication of Sn cap and SiNx cap Cu/Ta/SiO2 air-gap damascenes structures which includes the integration of electroplating copper, diffusion barrier Ta, sacrificial layer HSQ and capping layer Sn is the main goal in this thesis. The electromigration on this single damascene structure is also investigated. We developed the selective immersion plating Sn on copper, use Auger、GIAXRD to examine the composition of Sn thin film, and use AFM to measure the surface Morphology of Sn film. We mixed HSQ with MIBK at ratio=2:1 and spun it on SiO2 substrate. The HSQ film with pre-bake temperature 350℃ 3min is a good sacrificial layer. The cage-network-like HSQ can be removed by BOE solution easily from the interface with SiO2. Cu interconnect lines with width/space = 0.6/0.6μm deposited on Ta barrier layer are under chemical-mechical polished by using Al2O3 0.05μm particle with mixture HNO3 and Citric Acid , down force/back pressure varying 5.0/4.0、4.0/3.0、3.0/2.0 psi to remove Cu and by using Silica Levasil 50CK with H2O2 and H2O, D.F/B.P =3.0/2.0 to remove Ta. From the SEM pictures, We determine the best CMP conditions. Final, the Sn cap and SiNx cap Cu air-gap damascene structures with diffusion barrier Ta , sacrificial layer HSQ and capping layer Sn were fabricated. Sn cap and SiNx cap samples were studied by electromigration tests at 1750C with a current density of 4*106A/cm2, at pressure of 2 mtorr. The electromigration lifetimes for Sn cap air gap Cu interconnect lines were found to be longer than that of SiNx cap air gap Cu interconnect lines about 4.5 X. In order to determine the activation energy of electromigration, we measured the I-V under current stress at varying temperature with 1500C、1750C、2000C. The activation energy for Sn cap air-gap Cu interconnect lines is found to be 1.07eV.

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44

ChangJian, Hung-Yu, and 張簡鴻宇. "Magnetic Fiber Sensor By Using Air-Gap Long Period Grating." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/37610898719603333051.

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碩士
逢甲大學
電機工程所
98
The content of this thesis proposes the magnetic sensor based on an air-gap long period fiber grating (AG-LPG). This sensing device is composed of an AG-LPG fabricated by the semiconductor manufacturing process and surrounded with a smart materials-magnetic fluid. The AG-LPG is fabricated by combining the fiber side-polishing, fiber lithography and fiber etching method to produce the periodic air-gap grating in the core along the fiber axis of single mode fibers. Then, the grating region is immersed in the magnetic fluid and then packaged for achieving the magnetic sensor. The change of the surrounding refraction index (SRI) by magnetic field and the grating period will affect the resonant peak shift as well. For the measurement of forward DC magnetic field, the maximum shift of resonant wavelength of 14.4 nm in the field range from 3.3 to 114.8 Gauss is experimentally demonstrated with the sensitivity of about 0.12737nm / Gauss. For measuring the backward magnetic field, the experimental results demonstrated that the shift of resonant wavelength of 9 nm is obtained in the field range from -114.8 to -3.3 Gauss, which corresponds to the sensitivity of about -0.06778nm / Gauss. For the measurement of AC magnetic field, the frequency increment in the constant voltage will reduce the number of magnetic chains and then to decrease the refractive index of magnetic fluid materials, which will cause the wavelength shift toward the shorter-wavelength side. However, with increasing magnetic field-magnitude in a constant frequency, the index of magnetic fluid will increase due to the number increment of lead flux and then to cause the grating wavelength shift toward the longer-wavelength side. The novel magnetic fiber sensor can be applied in the measurement magnetic filed of dangerous or special environment.

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45

Fang, Michael Tianyu. "Suspended Trace Air-Gap Resonators for Low Loss Superconducting Circuits." Thesis, 2020. https://thesis.library.caltech.edu/13750/8/Fang_Michael_2020.pdf.

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Quantum memories and networks for distributed quantum information processing require links between the microwave, mechanical, and optical domains. Coherent integration of long-lived superconducting qubits (SCQs) with optomechanical and photonic devices (OMPDs) remains an outstanding challenge. We present a step towards coherent integration using a suspended trace air-gap resonator (STAR): a superconducting resonator on a silicon-on-insulator (SOI) substrate with the signal trace suspended by silicon tethers above and between galvanically connected ground metal planes. As a result, the electric field energy is closely confined within the microwave structure, yielding lower crosstalk compared to conventional coplanar waveguides (CPW). An order of magnitude improvement in the quality factors for STAR over previous work on SOI is achieved, in a transverse cross-sectional area that is an order of magnitude more compact. Electric field participation in lossy bulk dielectrics, a dominant source of energy leakage in previous measurements of aluminum CPW resonators on SOI, is virtually eliminated in STAR. The loss from the metal-air interface now dominates, but can be reduced by several factors using superconductors with better surface properties. Most importantly, STAR fabrication is compatible with Josephson junction and air-bridge deposition for highly coherent integration of SCQs and OMPDs to realize proposals for quantum information storage and networking.

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46

Lin, Yan-yu, and 林彥宇. "Magnetic Sensor Based on Air-Gap Long Period Fiber Gratings." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/05274353656223318625.

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碩士
逢甲大學
電機工程所
100
The magnetic sensors based on the air-gap long period fiber gratings (AG-LPG) on different types of fibers are presented in this thesis. The AG-LPG is fabricated by using the fiber side-polishing, fiber lithography and fiber etching techniques to produce the periodic air-gap grating in the core along the fiber axis both of single mode fibers and multi-mode fibers. Then, the grating region is immersed in the magnetic fluid and then packaged for achieving the magnetic sensor. This sensing mechanism is based on the resonance loss-dip wavelength shift of AG-LPG by the index change of magnetic fluid due to the variation of magnetic field strength. Further, the magnetic fiber sensor can provide another technique for measuring the high voltage electric current. The experimental results show that when the current is increased from 0.8A to 1A with the increment of 0.05A, the magnetic field intensity is increased from 226.79(Oe) to 392.91(Oe). The sensitivities of magnetic sensors both of AG-LPG on SMF and AG-LPG on MMF are 0.03147 nm/Oe and -0.3362 nm/Oe respectively. The sensitivity of the magnetic sensor can be improved for developing a wide range of magnetic sensing applications.

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47

Ying-HongChen and 陳盈宏. "Improvement of Optoelectronic Characteristics of GaN-based LED by Air Gap Array and Patterned Sapphire Substrates." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/82342646413640366211.

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48

Waters, Rafael. "Design of Air Gap Measuring system for Permanent Magnet Linear Generators." Thesis, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-162806.

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A novel concept for a wave power plant is being developed at the Division for Electricity and Lightning Research at Uppsala University. The concept is based on a permanent magnet linear generator placed on the seabed, directly driven by a surface following buoy. Critical for the survival of the generator is that the air gap between the moving and static parts of the generator is constantly fixed at the designed width to prevent the moving and static parts from connecting during operation. The aim of this thesis was the development and evaluation of a sensor for measuring the air gap during the operation of the generator. Additionally, in order to survive during years on the sea floor inside the wave power plants, the sensor was required to be a passive component, as well as robust and compact. A coil etched on a printed circuit board, i.e. a search coil, was the chosen basis for the sensor. The sensor was tested on an existing test rig of a wave power plant and the results were compared with theoretical calculations. The results show that a search coil magnetic sensor etched on a printed circuit board is a good concept for measuring the air gap. Experimentally measured and theoretically calculated sensor signals showed very good agreement. The designed sensor has a sensitivity of +/- 0.4 mm in the range of 4 – 9.5 mm air gap. The potential for future improvements of the sensor’s sensitivity is large.

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49

Dolan, Dale. "Modelling and Performance Evaluation of the Virtual Air Gap Variable Reactor." Thesis, 2009. http://hdl.handle.net/1807/17754.

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This thesis describes a novel device, the Virtual Air Gap Variable Reactor (VAG-VR), which is capable of producing a continuously variable reactance by locally saturating a small section of the reactor core via an embedded dc control winding. Variable Reactors have many applications in the power industry such as control of line power flow, voltage regulation, reactive line compensation and limiting inrush currents. A variable reactor is most commonly implemented as a thyristor controlled reactor (TCR) by switching in and out a constant reactance to achieve an averaged variable reactance. By using a virtual air gap, a continuously variable reactance is possible. The VAG-VR offers a better dynamic response, without introducing the harmonics created by the thyristor switching of a TCR. The VAG-VR gives low triplen harmonics and therefore allows control of reactive power in single phase or unbalanced three phase systems as would be required in the distribution system. An experimental prototype VAG-VR was developed to investigate three main performance measures: steady state performance, dynamic response and harmonic performance. Over the operating range of the VAG-VR inductance was varied from 100% to 9% of its original value. The dynamic response of the VAG-VR is approximately one tenth of a cycle. This compares favorably to a TCR which responds in approximately half a cycle. Harmonics are also shown to be significantly reduced in the VAG-VR compared to the TCR. A dynamic model of the VAG-VR, suitable for incorporation into power system simulations, was developed and validated. Parameters were determined both experimentally and through finite element method (FEM) simulations. Both experimental and simulation results indicate that the VAG-VR offers a technically viable alternative to the TCR.

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50

Hsieh, Cheng-Liang, and 謝政良. "Damascene Process for Air-gap Cu Interconnects Using Sacrificial layer HSQ." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/14671740737160959218.

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碩士
國立清華大學
電子工程研究所
94
Abstract The purpose of this study is to fabricate the SiNx capped Cu/Ta/SiO2 air-gap damascene structure. It included the integration of the sacrificial layer HSQ, diffusion barrier layer Ta, copper electroplating, and the passivation layer SiNx. The electric characteristic of the air-gap damascene structure was investigated, and discussed the leakage current and breakdown field. For the sacrificial layer, we spun HSQ with MIBK at ratio=2:1 on SiO2 substrate. It was found that with pre-bake temperature 350℃3min, HSQ was a good sacrificial layer. The cage-network-like HSQ can be removed by BOE solution easily from the interface with SiO2. For CMP, the Cu lines were defined with width/space = 0.5/0.5μm. The slurry mixed with Al2O3 particle (0.05μm)、 HNO3 and citric acid. The polishing down pressure /back pressure varied 5.0/4.0、4.0/3.0、3.0/2.0 psi to remove Cu film. The slurry for Ta is mixture of Levasil Silica 50CK、H2O2, and H2O. From the SEM pictures, the best CMP condition for the structure can be determined. The optimum D.P/B.P=5/2 psi is applied to remove Ta film. The SiNx capped Cu/Ta/SiO2 air-gap damascene structure with diffusion barrier layer Ta (150), the sacrificial layer HSQ and capped layer SiNx (200) was fabricated. The SiNx capped samples were studied by the I-V measurement. The leakage current measurement was done at different temperature(RT、50℃、100℃、150℃、180℃), and leakage current mechanism can be analyzed. The breakdown electric field was also measured at different temperature (RT、100℃、195℃) and analyzed. The SEM images were taken in order to correlate to the electrical breakdown measurements.

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Dissertations / Theses on the topic 'Air gap'

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