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Title: ASYMPTOTIC SIMILARITY IN TURBULENT BOUNDARY LAYERS
Creator: Duncan, Richard D.
Date: 2011-05-10, 2011-05
Description: The turbulent boundary layer is one of the most fundamental and important applications of fluid mechanics. Despite great practical interest...
Show moreThe turbulent boundary layer is one of the most fundamental and important applications of fluid mechanics. Despite great practical interest and its direct impact on frictional drag among its many important consequences, no theory absent of significant inference or assumption exists. Numerical simulations and empirical guidance are used to produce models and adequate predictions, but even minor improvements in modeling parameters or physical understanding could translate into significant improvements in the efficiency of aerodynamic and hydrodynamic vehicles. Classically, turbulent boundary layers and fully-developed turbulent channels and pipes are considered members of the same “family,” with similar “inner” versus “outer” descriptions. However, recent advances in experiments, simulations, and data processing have questioned this, and, as a result, their fundamental physics. To address a full range of pressure gradient boundary layers, a new approach to the governing equations and physical description of wall-bounded flows is formulated, using a two variable similarity approach and many of the tools of the classical method with slight but significant variations. A new set of similarity requirements for the characteristic scales of the problem is found, and when these requirements are applied to the classical “inner” and “outer” scales, a “similarity map” is developed providing a clear prediction of what flow conditions should result in self-similar forms. An empirical model with a small number of parameters and a form reminiscent of Coles’ “wall plus wake” is developed for the streamwise Reynolds stress, and shown to fit experimental and numerical data from a number of turbulent boundary layers as well as other wall-bounded flows. It appears from this model and its scaling using the free-stream velocity that the true asymptotic form of u′2 may not become self-evident until Re ≈ 275, 000 or δ+ ≈ 105, if not higher. A perturbation expansion made possible by the novel inclusion of the scaled streamwise coordinate is used to make an excellent prediction of the shear Reynolds stress in zero pressure gradient boundary layers and channel flows, requiring only a streamwise mean velocity profile and the new similarity map. Extension to other flows is promising, though more information about the normal Reynolds stresses is needed. This expansion is further used to infer a three layer structure in the turbulent boundary layer, and modified two layer structure in fully-developed flows, by using the classical inner and logarithmic profiles to determine which portions of the boundary layer are dominated by viscosity, inertia, or turbulence. A new inner function for U+ is developed, based on the three layer description, providing a much more simplified representative form of the streamwise mean velocity nearest the wall.
Ph.D. in Mechanical and Aerospace Engineering, May 2011
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Title: Laboratory Notebook 107
Creator: Cooper, Kerri, Lee, Alvin, Slade, Peter
Date: 2010-09-10T18:26:27Z
Description: Determining ozone's optimal conditions (contact time, concentration)

Title: High-order cumulants from the 3D O(1) and O(4) spin models, Proceedings of the XLIII International Symposium on Multiparticle Dynamics
Creator: Pan, Xue, Wu, Yuafang, Chen, X. S., Chen, Lizhu
Date: 2013-09-15, 2013-09-15
Publisher: IIT Press
Description: We simulate the 3D O(1) (Ising) and O(4) spin models by the Monte Carlo method. Interesting high-order cumulants from the 3D Ising and O(4)...
Show moreWe simulate the 3D O(1) (Ising) and O(4) spin models by the Monte Carlo method. Interesting high-order cumulants from the 3D Ising and O(4) universality classes are presented and discussed. They all show the non-monotonic or sign change behavior. The critical behavior is instructive to that of the high-order cumulants of the net baryon number in the QCD phase transitions. Maybe it’s difficult to distinguish the universality classes by the high-order cumulants in the heavy ion collisions.
Sponsorship: IIT College of Science, High Energy Physics Division of Argonne National Laboratory
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Title: PA 508 Library Instruction
Creator: Ahrens, Aric G.
Date: 2010-01-15, 2010-01-15
Description: This PowerPoint presentation was given to the Chinese contingent of the Master of Public Administration Graduate Program during Spring...
Show moreThis PowerPoint presentation was given to the Chinese contingent of the Master of Public Administration Graduate Program during Spring Semester 2010. It covers basic research and library skills.
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Title: Cavity Resonance Suppression Using Miniature Fluidic Oscillators
Creator: Raman, G., Raghu, S.
Date: 2004-12
Publisher: American Inst Aeronaut Astronaut

Title: Nonlinear Interactions as Precursors to Mode Jumps in Resonant Acoustics
Creator: Panickar, P., Srinivasan, K., Raman, G.
Date: 2005-09
Publisher: American Inst Physics
Description: This paper examines instability mode switching in various supersonic jet configurations that involve resonant acoustics. Resonant acoustics...
Show moreThis paper examines instability mode switching in various supersonic jet configurations that involve resonant acoustics. Resonant acoustics includes situations where flow instabilities are enhanced by feedback. The pressure spectra in such situations are rich in multiple modes, and mode switching can occur rather unpredictably. Our experiments reveal that mode switching and the number of nonlinear interactions are interconnected and this number increases just prior to a mode switch. We quantified nonlinear interactions by counting the number of such interactions occurring over a threshold level in the nonlinear cross-bicoherence spectrum and confirmed that nonlinear interactions are precursors to mode jumps. Further, this result was found to be independent of the threshold level. Moreover, if more than one instability mode coexisted, the decay of one and the persistence of the other caused a similar increase in nonlinearities. On the other hand, if there was no mode switch, the nonlinearities remained at comparable limits over the entire operating range. The latter part of the work focused on why difference interactions significantly outnumbered sum interactions in the spectra of shock-containing resonant flows. Using linear stability calculations it is shown that most of the difference interactions that occurred had a positive spatial growth rate and were, hence, unstable. In contrast, a majority of the sum interactions lay outside the amplified region which indicated that they tend to decay spatially. (c) 2005 American Institute of Physics.
http://dx.doi.org/10.1063/1.2008995
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Title: Mixer-ejector Wall Pressure and Temperature Measurements Based on Photoluminescence
Creator: Taghavi, R.r., Raman, G., Bencic, Tj
Date: 2002-04
Publisher: American Inst Aeronaut Astronaut
Description: Ejector side-wall pressure distribution is a key indicator of supersonic jet-mixer-ejector performance. When documenting pressure patterns on...
Show moreEjector side-wall pressure distribution is a key indicator of supersonic jet-mixer-ejector performance. When documenting pressure patterns on an ejector wall using pressure-sensitive paint (PSP), one has to consider temperature variations caused by the supersonic jet flow within the ejector because these can cause significant local errors in the PSP results. If the temperature sensitivity of PSP is not corrected for in complex internal supersonic flows, large localized errors could contaminate the results. In the present work, temperature-sensitive paint maps the temperature distribution on the ejector wall and corrects PSP results point-by-point for temperature sensitivity. The experiments were conducted on multijet supersonic mixer-ejector configurations with straight, convergent (6-deg), and divergent (6-deg) side walls. A comparison of corrected and uncorrected PSP readings shows that at M-j = 1.55, the error with respect to true data from static pressure ports can be reduced from 4.98 to 2.84% for the case of a simple ejector with parallel walls. For the complex 6-deg convergent ejector at M-j = 1.39, the error reduces by almost an order of magnitude (from 20.83 to 2.66%). Our results indicate that the use of this correction technique can significantly reduce PSP errors in complex internal supersonic flow situations.
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Title: MECHANICAL PROPERTIES AND SINTERING MECHANISMS OF POWDER METALLURGY TI6AL4V
Creator: Xu, Xiaoyan
Date: 2013, 2013-05
Description: Titanium has been identified as one of the key materials with a high strength to weight ratio that can reduce the weight of components and...
Show moreTitanium has been identified as one of the key materials with a high strength to weight ratio that can reduce the weight of components and thereby reduce energy consumption. Single press and sinter as a powder metallurgy technique has the potential to provide cost effective components. Armstrong prealloyed Ti6Al4V, HDH prealloyed Ti6Al4V, HDH blended Ti6Al4V powder and their mixtures were pressed and sintered at different conditions. The chemistry, mechanical and microstructural properties have been investigated to establish optimum processing parameters. Sintered parts were sent to Oshkosh Truck to test and compared with aluminum and steel parts. The Titanium and Ti6Al4V parts were successfully applied and tested. All the specimens passed the load test without failures. The sintering mechanisms of Armstrong prealloyed Ti6Al4V powder were investigated. At relative sintered densities of 75% to 90% (around 900°C), surface diffusion cooperate with grain boundary diffusion, which leads to densification of the powder compact. Around 900°C, grain boundary diffusion controls the sintering process. At 1000°C, boundary diffusion made little contribution to the densification of the Ti6Al4V powder compact. Above 900°C and below 91% sintered density, boundary diffusion controls sintering. Lattice diffusion dominates the densification process at higher temperatures (1100°C~1300°C). The sintering of master alloy blended Ti6Al4V powder has been investigated in order to elucidate the mechanism of sintering. Both blended powder compacts and diffusion couples were investigated using backscattered imaging and energy xvi dispersive analysis to determine the phases present and diffusion path on sintering at 1000ºC and 1100ºC. It is shown that transient liquid phase sintering does not occur and the reason for the rapid sintering of this material is due to enhanced diffusion kinetics resulting from a combination of the concentration gradient and stress induced by a phase transformation in the ternary system.
PH.D in Materials Science and Engineering, May 2013
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Title: Empirical modeling of systems with output multiplicities by multivariate additive NARX models
Creator: Decicco, J., Cinar, A.
Date: 2000-06
Publisher: AMER CHEMICAL SOC
Description: Multivariable additive NARX (nonlinear autoregressive with exogenous inputs) modeling of process systems is presented. The model structure is...
Show moreMultivariable additive NARX (nonlinear autoregressive with exogenous inputs) modeling of process systems is presented. The model structure is similar to that of a generalized additive model (GAM) and is estimated with a nonlinear canonical variate analysis (CVA) algorithm called CANALS. The system is modeled by partitioning the data into two groups of variables. The first is a collection of future outputs, and the second is a collection of past input and outputs and future inputs. This approach is similar to linear subspace state-space modeling. An illustrative example of modeling is presented on the basis of a simulated continuous chemical reactor that exhibits multiple steady states in the outputs for a fixed level of the input.
Endnote format citation for DOI:10.1021/ie9906464
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Title: Laboratory Notebook 112
Creator: Zhang, Zhe, Varelis, Peter
Date: 2010-03-09T22:34:24Z
Description: This laboratory notebook relates to the "Heat Stability of Ricin in Phosphate Buffer System" project with Peter Varelis as the Principle...
Show moreThis laboratory notebook relates to the "Heat Stability of Ricin in Phosphate Buffer System" project with Peter Varelis as the Principle Investigator.
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Title: Development of High Bandwidth Powered Resonance Tube Actuators with Feedback Control
Creator: Raman, G., Khanafseh, S., Cain, A. B., Kerschen, E.
Date: 2004-01-22
Publisher: Academic Press Ltd Elsevier Science Ltd
Description: A high bandwidth powered resonance tube (PRT) actuator potentially useful for noise and flow control applications was developed. High...
Show moreA high bandwidth powered resonance tube (PRT) actuator potentially useful for noise and flow control applications was developed. High bandwidth allows use of the same actuator at various locations on an aircraft and over a range of flight speeds. The actuator selected for bandwidth enhancement was the PRT actuator, which is an adaptation of the Hartmann whistle. The device is capable of producing high-frequency and high-amplitude pressure and velocity perturbations for active flow control applications. Our detailed experiments aimed at understanding the PRT phenomenon are complemented by an improved analytical model and direct numerical simulations. We provide a detailed characterization of the unsteady pressures in the nearfield of the actuator using phase averaged pressure measurements. The measurements revealed that propagating fluctuations at 9 kHz were biased towards the upstream direction (relative to the supply jet). A complementary computational study validated by our experiments was useful in simulating the details in the region between the supply jet and the resonance tube where it was difficult to gather experimental data. High bandwidth was obtained by varying the depth of the resonance tube that determines the frequency produced by the device. Our actuator could produce frequencies ranging from 1600 to 15,000 Hz at amplitudes as high as 160 dB near the source. The frequency variation with depth is predicted well by the quarter wavelength formula for deep tubes but the formula becomes increasingly inaccurate as the tube depth is decreased. An improved analytical model was developed, in which the compliance and mass of the fluid in the integration slot is incorporated into the prediction of resonance frequencies of the system. Finally a feedback controller that varied both the resonance tube depth and spacing to converge on a desired frequency was developed and demonstrated. We are optimistic that numerous potential applications exist for such high bandwidth high dynamic range actuators. (C) 2003 Published by Elsevier Science Ltd.
http://dx.doi.org/10.1016/S0022-460X(03)00212-8
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Title: EUTECTIC γ(NI)/γ′(NI3AL)-δ(NI3NB) POLYCRYSTALLINE NICKEL-BASE SUPERALLOYS: CHEMISTRY, PROCESSING, MICROSTRUCTURE AND PROPERTIES
Creator: Xie, Mengtao
Date: 2012-12-03, 2012-12
Description: Directionally solidified γ(Ni)/γ′(Ni3Al)-δ(Ni3Nb) eutectic alloys possess attrac- tive high temperature mechanical properties and were...
Show moreDirectionally solidified γ(Ni)/γ′(Ni3Al)-δ(Ni3Nb) eutectic alloys possess attrac- tive high temperature mechanical properties and were considered as candidate tur- bine blade materials. Currently, the properties of polycrystalline γ/γ′-δ alloys are of interest as they inherit many advantageous attributes from the directionally solidi- fied γ/γ′-δ alloys, including high volume fraction of reinforcing phases, exceptional thermal stability and resistance to segregation-induced defect formation. If these at- tributes are properly harnessed, these γ/γ′-δ eutectic alloys might provide a unique solution to the problems experienced by traditional γ/γ′ polycrystalline Ni-base su- peralloys. This thesis is therefore dedicated towards the development of a funda- mental understanding of this novel class of eutectic alloys from several important perspectives. To enrich our understanding of this alloy system, this thesis will first be focused on quantifying the specific effect of individual alloying element on this γ/γ′-δ eutectic system. A set of quaternary Ni-Cr-Al-Nb alloy compositions with increasing levels of Chromium(Cr) was designed to investigate the detailed influence of this element on the primary phase formation, solidus and liquidus temperatures and γ-δ eutectic morphology. The alloying effect of Tantalum(Ta), which shares many similarities to Niobium(Nb), was studied by designing a matrix of multi-component γ/γ′-δ alloy compositions with nominally the same overall (Ta+Nb) content but varying Ta/Nb ratios. Here, different solidification segregation and solid state partitioning behaviors of Ta and Nb in this γ/γ′-δ eutectic system will be discussed, as well as the influ- ence of Ta/Nb ratio on solidification characteristics and equilibrium/non-equilibrium phase volume fractions. Thermodynamic calculations using the Computherm Pandat database (PanNi7) were compared to experimental results in these investigations. The second part of this thesis will aim to provide a more general understand- xvii ing of the effect of various alloying elements, including Cr, Co, Al, Ti, Mo, W, Ta and Nb, on this γ/γ′-δ system. A large number of experimental γ/γ′-δ alloys covering a broad range of compositions was selected for the analysis in this study. Important alloy attributes, such as primary phase formation, overall δ volume fraction, phase transformation temperatures and ternary eutectic initiation, were quantitatively char- acterized as a function of individual alloying element concentrations or combined con- tent of more elements. Linear regression analysis was performed to reveal the relative effectiveness of these elements on this eutectic system. Meanwhile, an extensive com- parison between the experimental observations and Pandat predictions was provided to critically evaluate the strength and weakness of existing thermodynamic database model in predicting trends in this eutectic alloy system with substantially higher Nb content compared to traditional γ/γ′ superalloys. The last part of this thesis emphasizes the development of cast and wrought manufacturing processes for cast γ/γ′-δ eutectic alloys as a cost effective alternative to the powder metallurgy route. Hot rolling of workpieces encapsulated within a steel can was performed on a simple model cast γ/γ′-δ alloy (897) to stimulate the ingot to billet. The influence of different deformation levels on breaking down the dendritic structure and promoting fine and homogenized microstructure was investi- gated. The mechanical soundness associated with different microstructures generated by different hot rolling processes was compared via compression and creep testing. Microstructural parameters that contribute to better mechanical properties will be discussed.
PH.D in Materials Science and Engineering, December 2012
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Title: Influence of the target on multiparticle production in the forward domain in p+Pb collisions at 158 GeV, Proceedings of the XLIII International Symposium on Multiparticle Dynamics
Creator: Rybczyński, Maciej
Date: 2013-09-15, 2013-09-15
Publisher: IIT Press
Description: In this talk we show the influence of the target on multiparticle production in the forward hemisphere in p+Pb collisions at top SPS energy....
Show moreIn this talk we show the influence of the target on multiparticle production in the forward hemisphere in p+Pb collisions at top SPS energy. The multiplicity distributions appear to be almost target independent in the projectile fragmentation domain and the effect of fluctuations of the number of target participants is not seen in the projectile fragmentation region. We compare the obtained results with those for p+p interactions and predictions of models.
Sponsorship: IIT College of Science, High Energy Physics Division of Argonne National Laboratory
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Title: Widget Applications to Enhance the Tru2Way Consumer Experience (sequence unknown), IPRO 312 - Deliverables
Creator: Alsharief, Yagoob, Aulfata, Muluken, Curtis, Christopher, Dhewaju, Anusuya, Mooney, Kevin, Mutyaba, Kevin, Ndoping, Marco, Onaissi, Samah, Peterson, Naomi, Siwek, Steven, Wallace, Sean, Yi, Won-jae
Date: 2009-12
Description: The IPRO teams objectives are to provide Comcast with feedback from an outside perspective, allowing them to see where their Tru2Way system...
Show moreThe IPRO teams objectives are to provide Comcast with feedback from an outside perspective, allowing them to see where their Tru2Way system needs additional attention or support.
Sponsorship: Comcast
Deliverables for IPRO 312: Widget Applications to Enhance the Tru2Way Consumer Experience for the fall 2009 semester
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Title: MONITORING, MODELING, AND TREATMENT OF ODORS/ODORANTS AT WATER RECLAMATION PLANTS
Creator: Zhang, Yanming
Date: 2012-04-23, 2012-05
Description: A thorough study including odor monitoring, modeling and treatment as three important aspects of odor control in WRPs has been performed in...
Show moreA thorough study including odor monitoring, modeling and treatment as three important aspects of odor control in WRPs has been performed in this research. Measurement of H2S emissions from odor sources was proven to be an essential step in odor monitoring program. The H2S emission rates were measured from various sources throughout a WRP for 9 sampling events during winter and summer. During summer, both the average and the maximum emission rates of H2S from liquid treatment processes increased significantly compared to those measured during winter. However, for solids-handling processes, the emission rates remained constant because sludge characteristics did not vary throughout the year. The total sulfide concentrations present in liquid treatment processes were higher than those in preliminary and primary treatment units but at much lower levels in secondary treatment. Rates of H2S emission from the headworks were correlated to daily average wastewater temperature, TKN concentration, and flow rate. AERMOD was used as the modeling tool to evaluate the odor impact of Egan WRP on the surrounding communities. The emission rates could significantly affect the modeling results. Long-term H2S monitoring increases the possibility of developing the proper emission rate for the worst-case scenario. Excluding the modeling during the night would avoid overestimation of odor impact and excessive odor control. In the laboratory-scale study of O3 oxidation of H2S, O3 oxidation was proven to be a fast and effective method to remove H2S from the odorous air emitted from wastewater treatment processes. The increased initial ratio of O3/H2S enhances the removal rate of H2S. The consumption ratio of O3/H2S is a function of input reactant ratios. A multiple linear regression model (R2=0.84) has been developed to predict the H2S residual for given initial H2S and O3 concentrations and reaction time. The increased moisture content of the odorous air enhanced the H2S removal while DMS and DMDS inhibit H2S removal by competing for the limited O3 supply.
Ph.D. in Environmental Engineering, May 2012
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Title: AN ADAPTIVE RESCALING SCHEME FOR COMPUTING HELE-SHAW PROBLEMS
Creator: Zhao, Meng
Date: 2017, 2017-07
Description: In this thesis, we develop efficient adaptive rescaling schemes to investigate interface instabilities associated with moving interface...
Show moreIn this thesis, we develop efficient adaptive rescaling schemes to investigate interface instabilities associated with moving interface problems. The idea of rescaling is to map the current time-space onto a new time-space frame such that the interfaces evolve at a chosen speed in the new frame. We couple the rescaling idea with boundary integral method to demonstrate the efficiency of the rescaling idea, though it can be applied to Cartesian-grid based method in general. As an example, we use the Hele-Shaw problem to examine the efficiency of the rescaling scheme. First, we apply the rescaling scheme to a slowly expanding interface. In the new frame, the evolution is dramatically accelerated, while the underlying physics remains unchanged. In particular, at long times numerical results reveal that there exist nonlinear, stable, self-similarly evolving morphologies. The rescaling idea can also be used to simulate the fast shrinking interface, e.g. the Hele-Shaw problem with a time dependent gap. In this case, the rescaling scheme slows down the interface evolution in the new frame to remove the severe time step constraint that makes the long-time simulations prohibitive. Finally, we study an analytical solution to the stability of the interface of the Hele-Shaw problem, assuming a small surface tension under a time dependent flux Q(t). Following [116, 109], we find the motions of daughter singularity ζd and simple singularity ζ0 do not depend on the flux Q(t). We also find a criterion to identify the relation between ζ0 and ζd.
Ph.D. in Applied Mathematics, July 2017
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Title: Aeroacoustic Features of Coupled Twin Jets with Spanwise Oblique Shock-Cells
Creator: Panickar, P., Srinivasan, K., Raman, G.
Date: 2004-11-22
Publisher: Academic Press Ltd Elsevier Science Ltd
Description: This paper experimentally investigates the aeroacoustics of coupled twin jets of complex geometry. The study was motivated by the fact that...
Show moreThis paper experimentally investigates the aeroacoustics of coupled twin jets of complex geometry. The study was motivated by the fact that twin jet configurations that are commonly used in aircraft propulsion systems can undergo unpredictable resonant coupling resulting in structural damage. Further, nozzles with spanwise oblique exits are increasingly being considered for their aerodynamic and acoustic advantages, as well as stealth benefits. Although several studies have examined aspects of twin jet coupling, very little data is available on the coupling of jets from nozzles of complex geometry. Our study focuses on twin convergent nozzles with an aspect ratio of 7 with spanwise oblique exits operated over the fully expanded Mach number range from 1.3 to 1.6. The inter-nozzle spacing (s/h) was varied from 7.4 to 13.5. However, the focus remained on the lower spacing that is more representative of aircraft applications. Several interesting results have emerged from this study: (1) Coupling of twin nozzles with a beveled exit was observed only when the beveled edges faced each other and the nozzles formed a 'V' shape in the inter-nozzle region. Specifically, if the two beveled edges were oriented away from each other to form an arrowhead (W) shape no coupling was observed. (2) Despite the presence of spanwise antisymmetric, spanwise symmetric and spanwise oblique modes for the single nozzles, only the first two modes were evident in the coupling. (3) The symmetric coupling produced unsteady pressures in the inter-nozzle region that were up to 7.5 dB higher than the antisymmetrically coupled case. (4) Dynamic tests conducted by moving the nozzles apart while they were operating or by continuously changing the stagnation pressure at fixed inter-nozzle spacing revealed that coupling modes could co-exist at non-harmonically related frequencies. These dynamic tests reproduced the static test data. (5) The frequency of both coupling modes agrees with the higher order waveguide modes based on Tam's theory. (6) Differences in broadband shock noise between the 'V' and 'A' configurations were also documented. Our results provide an understanding of complex twin jet coupling and will serve as benchmark data for validating computational models. (C) 2003 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.jsv.2003.10.011
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Title: The potential importance of low luminosity and high energy at the LHC, Proceedings of the XLIII International Symposium on Multiparticle Dynamics
Creator: White, Alan R.
Date: 2013-09-15, 2013-09-15
Publisher: IIT Press
Description: Low luminosity runs at higher LHC energy could provide definitive evidence for an electroweak scale sextet quark sector of QCD that produces...
Show moreLow luminosity runs at higher LHC energy could provide definitive evidence for an electroweak scale sextet quark sector of QCD that produces electroweak symmetry breaking and dark matter within the bound-state S-Matrix of QUD - a massless, weak coupling, infra-red fixed-point, SU(5) field theory that might underly and unify the full Standard Model.
Sponsorship: IIT College of Science, High Energy Physics Division of Argonne National Laboratory
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Title: WIRELESS SCHEDULING IN MULTI-CHANNEL MULTI-RADIO MULTIHOP WIRELESS NETWORKS
Creator: Wang, Zhu
Date: 2014, 2014-07
Description: Maximum multi ow (MMF) and maximum concurrent multi ow (MCMF) in multi-channel multi-radio (MC-MR) wireless networks have been well-studied in...
Show moreMaximum multi ow (MMF) and maximum concurrent multi ow (MCMF) in multi-channel multi-radio (MC-MR) wireless networks have been well-studied in the literature. They are NP-hard even in single-channel single-radio (SC-SR) wireless networks when all nodes have uniform (and xed) interference radii and the positions of all nodes are available. This disertation studies maximum multi ow (MMF) and maximum concur- rent multi ow (MCMF) in muliti-channel multi-radio multihop wireless networks under the protocol interference model in the bidirectional mode or the unidirectional mode. We introduce a ne-grained network representation of multi-channel multi- radio multihop wireless networks and present some essential topological properties of its associated con ict graph. It was proved that if the number of channels is bounded by a constant (which is typical in practical networks), both MMF and MCMF admit a polynomial-time ap- proximation scheme under the protocol interference model in the bidirectional mode or the unidirectional mode with some additional mild conditions. However, the run- ning time of these algorithms grows quickly with the number of radios per node (at least in the sixth order) and the number of channels (at least in the cubic order). Such poor scalability stems intrinsically from the exploding size of the ne-grained network representation upon which those algorithms are built. In Chapter 2 of this dissertation, we introduce a new structure, termed as concise con ict graph, on the node-level links directly. Such structure succinctly captures the essential advantage of multiple radios and multiple channels. By exploring and exploiting the rich structural properties of the concise con ict graphs, we are able to develop fast and scalable link scheduling algorithms for either minimizing the communication latency or maximizing the (concurrent) multi ow. These algorithms have running time growing linearly in both the number of radios per node and the number of channels, while not sacri cing the approximation bounds. While the algorithms we develop in Chapter 2 admit a polynomial-time ap- proximation scheme (PTAS) when the number of channels is bounded by a constant, such PTAS is quite infeasible practically. Other than the PTAS, all other known approximation algorithms, in both SC-SR wireless networks and MC-MR wireless networks, resorted to solve a polynomial-sized linear program (LP) exactly. The s- calability of their running time is fundamentally limited by the general-purposed LP solvers. In Chapter 3 of this dissertation, we rst introduce the concept of interference costs and prices of a path and explore their relations with the maximum (concurrent) multi ow. Then we develop purely combinatorial approximation algorithms which compute a sequence of least interference-cost routing paths along which the ows are routed. These algorithms are faster and simpler, and achieve nearly the same approximation bounds known in the literature. This dissertation also explores the stability analysis of two link scheduling in MC-MR wireless networks under the protocol interference model in the bidirectional mode or the unidirectional mode. Longest-queue- rst (LQF) link scheduling is a greedy link scheduling in multihop wireless networks. Its stability performance in single-channel single-radio (SC-SR) wireless networks has been well studied recently. However, its stability performance in multi-channel multi-radio (MC-MR) wireless networks is largely under-explored. We present a stability subregion with closed form of the LQF scheduling in MC-MR wireless networks, which is within a constant factor of the network stability region. We also obtain constant lower bounds on the efficiency ratio of the LQF scheduling in MC-MR wireless networks under the protocol interference model in the bidirectional mode or unidirectional mode. Static greedy link schedulings have much simpler implementation than dy- namic greedy link schedulings such as Longest-queue-frst (LQF) link scheduling. However, its stability performance in multi-channel multi-radio (MC-MR) wireless networks is largely under-explored. In this dissertation, we present a stability subre- gion with closed form of a static greedy link scheduling in MC-MR wireless networks under the protocol interference model in the bidirectional mode. By adopting some special static link orderings, the stability subregion is within a constant factor of the stable capacity region of the network. We also obtain constant lower bounds on the throughput efficiency ratios of the static greedy link schedulings in some special static link orderings.
Ph.D. in Computer Science, July 2014
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Title: Presentation to CARLI collections group
Creator: Uth, Charles
Date: 2010-04-13T13:25:24Z

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