University of Manitoba Scholarship (login required)

Permanent URI for this collection

http://hdl.handle.net/1993/2762

Browse

Now showing 1 - 20 of 171

Restricted
The 2003 R.M. Hardy lecture: Soil parameters for numerical analysis in clay
(2006-02-01T11:58:14Z) Graham, J
Engineers in geotechnical practice work on increasingly complex problems with increasingly powerful numerical tools. Effective solutions to design problems need good information about the site and parameters (or functions) that describe how the soil will behave under the proposed loadings. These loadings can include heating, drying or wetting, time effects, and chemical changes as well as the more common structural loads. This paper outlines issues that need to be considered when laboratory tests are used to produce soil properties for use in numerical analyses. The focus is on soft to moderately stiff saturated clays. Similar considerations for in situ tests, stiff clays, and sands are not considered.
Restricted
Ab initio analysis of C-H and C-C stretching intensities in Raman spectra of hydrocarbons
(2005-03-31) Gough, KM; Dwyer, JR; Dawes, R
Molecular polarizability and changes in the polarizability associated with the stretch of C-C and C-H bonds have been calculated for thirty-four saturated hydrocarbons, including the series of n-alkanes to C15, as well as several cyclo- and bicycloalkanes, propellanes, prismanes, and hedranes. The ab initio results (HF/D95(d,p)) are compared to experimental Raman trace scattering intensities where such information is available. Possible factors governing trends in the magnitude of the derivatives are considered. For the C-C stretches, chain length and position along the chain are the most important factors for the n-alkanes, whereas strain appears to be significant for the ring and caged structures. For the C-H stretches, the most significant factors are the same as those found in our earlier work: location, type, and orientation relative to the carbon skeleton.
Restricted
Acoustic discharge measurements for the performance testing of low-head hydroelectric turbines under disturbed flow conditions
(2000-02-29T12:43:11Z) Doering, JC; Gawne, KD
The detection, measurement, and characterization of frazil ice particles is a necessary first step in advancing our understanding of frazil ice processes as well as improving models. The detection of frazil ice has been accomplished in a number of ways. Herein, a digital image processing system to characterize frazil in a laboratory environment is described. The system is part of an ice research facility that uses a counter-rotating flume to generate frazil ice. Frazil ice is detected using a cross-polarized light technique. The system acquires digital gray-scale images of frazil ice that are analyzed and manipulated digitally to elucidate the temporal and spatial variation of frazil ice characteristics. For example, the system can be readily used to determine the size distribution of frazil ice particles, the vertical distribution of frazil, or the concentration of frazil ice.
Restricted
Adaptive fair subcarrier/rate allocation in multirate OFDMA networks: Radio link level queuing performance analysis
(2006-11-30T12:34:15Z) Niyato, D; Hossain, E
This paper presents a semi-analytical methodology for radio link level performance analysis in a multirate "orthogonal frequency-division multiple-access" (OFDMA) network with adaptive fair rate allocation. Multirate transmission is assumed to be achieved through adaptive modulation, and fair rate allocation-is based on the principle of generalized processor sharing to allocate the subcarriers adaptively among the users. The fair rate allocation problem is formulated as an optimization problem with the objective of maximizing system throughput while maintaining fairness (in terms of transmission rate) among the users. The "optimal" fair rate allocation is obtained by using the "Hungarian method." A heuristic-based approach, namely the "iterative approach," that is more implementation friendly is also presented. The throughput performance of the iterative fair rate allocation is observed to be as good as that of optimal fair rate allocation and is better than that of the static subcarrier allocation scheme. Also, the iterative fair allocation provides better fairness compared to that for each of the optimal and the static subcarrier allocation schemes. To this end, a queuing model is formulated to analyze radio link level performance measures such as packet dropping probability and packet transmission delay under the above rate allocation schemes. In this formulation, packet arrivals are modeled by the discrete Markov modulated Poisson process, which is flexible to model different types of traffic arrival patterns. The proposed framework for radio link level performance analysis of multirate OFDMA networks is validated by extensive simulations. Also, examples on the application of the proposed model for connection admission control and quality-of-service provisioning are illustrated.
Restricted
Analysis of finite-micro strip structures using surface equivalence principle and multiple network theory (SEMN)
(2002-08-31T12:39:54Z) Tavakkol-Hamedani, F; Tavakoli, A; Shafai, L
Two techniques based on electric and magnetic field integral equation (EFIE and MFIE) formulations of surface equilalent principle and multiple network theory (SEMN) method are developed for the analysis of finite microstrip structures. Using pulse surface basis functions, the surface of each homogeneous dielectric body is modeled by small flat segments of arbitrary geometry and constant electromagnetic field. Using the surface equivalence principle and the Green's functions of the homogeneous space, the admittance and impedance matrices are computed. Then, the boundary conditions and multiple network theory are applied to determine the overall characteristic of the entire space. Several radiation and scattering examples are numerically analyzed and their calculated near and far fields are presented. The numerical results of the two formulations are then compared with measurement and those of HFSS and ENSEMBLE.
Restricted
Analysis of NRD waveguide-based components and transitions using the TLM-based modal extraction approach
(2006-12-31T12:53:37Z) Ghosh, B; Simons, NRS; Shafai, L; Ittipboon, A; Petosa, A
This paper presents a full-wave modal analysis of several typical components based on a nonradiative dielectric (NRD) waveguide technology using the transmission line matrix (TLM)-based modal extraction approach (TMEA) for the first time. It also presents a full-wave analysis of a slot-coupled microstrip-to-NRD waveguide transition, evaluating the modes excited in the NRD waveguide. The components studied using this approach include a two-pole air gap-coupled NRD-waveguide bandpass filter. an LSM-LSE mode transducer and an open-ended NRD waveguide. Previous study of these components focussed only on the LSM01 mode. Also, die only previous work investigating a slot-coupled microstrip-to-NRD geometry while taking into consideration the modes propagating in the NRD waveguide used the high-frequency structure simulator to model the transition. It is shown in this work that the TMEA can be extended to perform a rigorous modal analysis of NRD waveguide-based components and the microstrip-to-NRD waveguide transition, taking into account all propagating modes in the NRD waveguide. Results obtained using this method have been verified using the power conservation theorem and the Poynting theorem. The results show for the first time that nonorthogonal leak-age can complicate the performance of certain NRD waveguide-based components like the LSM-LSE mode transducer.
Restricted
Analysis of restriction fragment length polymorphisms in the ribosomal DNA of a selection of anaerobic chytrids
(2000-07-31T18:16:36Z) Hausner, G; Inglis, G; Yanke, LJ; Kawchuk, LM; McAllister, TA
Anaerobic chytrid strains (representing four genera and seven species based on morphological characters), obtained from a variety of hosts, were analysed for variability within the 5' terminal segment of the ribosomal large subunit (LSU) gene, first internal transcribed spacer (ITS1), and the intergenic spacers (IGS) of the ribosomal repeat unit. In the analyses of the ribosomal LSU gene, strains of Neocallimastix, Orpinomyces, and Anaeromyces clustered into distinct groups, but Piromyces strains did not. Although the size of polymerase chain reaction products for the ITS1 region varied among strains, restriction fragment length polymorphism analysis was not useful in distinguishing between the strains. In the analyses of restriction fragment profiles of the IGS, strains of Orpinomyces and Anaeromyces clustered into distinct groupings that corresponded with morphological characters. In contrast, Neocallimastix strains clustered into two distinct groups. Considerable variability was observed in the IGS for strains of Piromyces. Analysis of this region split strains of Piromyces rhinzinflata obtained from a single bison into at least two distinct genetic groupings. Furthermore, the Piromyces strains obtained from bovine, wapiti, and moose clustered according to host. Overall, our molecular data suggest that morphological characters as observed under the light microscope are insufficient for the designation of phylogenetic species of Neocallimastix and Piromyces, and that integration of molecular and morphological data will be required to establish a natural classification system for the anaerobic members of the Chytridiomycota.
Restricted
Analysis of TCP performance under joint rate and power adaptation in cellular WCDMA networks
(2004-05-31T12:50:28Z) Hossain, E; Kim, DI; Bhargava, VK
To improve the spectral efficiency while meeting the radio link level quality of service requirements such as the bit-error-rate (BER) requirements for the different wireless services, transmission rate and power corresponding to the different mobile users can be dynamically varied in a cellular wideband code-division multiple-access (WCDMA) network depending on the variations in channel interference and fading conditions. This paper models and analyzes the performance of transmission control protocol (TCP) under joint rate and power adaptation with constrained BER requirements for downlink data transmission in a cellular variable spreading factor (VSF) WCDMA network. The aim of this multilayer modeling of the WCDMA radio interface is to better understand the interlayer protocol interactions and identify suitable transport and radio link layer mechanisms to improve TCP performance in a wide-area cellular WCDMA network.
Restricted
An analytical approach to providing controllable differentiated quality of service in Web servers
(2005-11-30) Rashid, MM; Alfa, AS; Hossain, E; Maheswaran, M
Provisioning quality of service (QoS) in Web servers has gained immense importance because Web servers are a major part of the Internet. To deliver the pledged QoS, Web service providers need control over the allocation of the resources in their Web servers. Control is also necessary for reaching the optimal resource allocation through proper service differentiation. In this paper, we propose and investigate an analytic approach that enables the service providers to deploy a differentiated service policy that offers this control. The proposed service policy is configurable by tunable control parameters. We devise the relationships between the performance measures and these parameters by adopting a unique queuing theoretic approach. Once these relationships are established, we describe how these parameters can be set to their most appropriate values depending on the objectives of the service providers. We illustrate the usefulness of our approach by conducting the analysis on a real Web trace.
Restricted
Antiviral activity of arylnaphthalene and aryldihydronaphthalene lignans
(2003-03-31) Cow, C; Leung, C; Charlton, JL
A practical method for large scale synthesis of 1-arylnaphthalene and 1-aryl-1,2-dihydronaphthalene lignans is described. The method makes use of the classic Stobbe condensation followed by regioselective reactions that provide access to both the common and retrolactone lignans, e.g., 2 and 3. A total of 25 compounds, many of which are known natural products, were prepared and their antiviral activity against human cytomegalovirus measured.
Restricted
Artificial inoculation with Armillaria ostoyae in established conifers stressed by defoliation, planting, and thinning in Newfoundland
(2000-11-30) Piercey-Normore, MD; Berube, JA
Armillaria ostoyae (Romagnesi) Herink causes root disease in conifers of the northern hemisphere. Pathogenicity tests of established conifer trees with A. ostoyae, has never been done in the boreal forest. Seven forest plots were selected in Newfoundland; a black spruce (Picea mariana (Mill.) BSP) plantation, a naturally regenerated black spruce stand, a balsam fir (Abies balsamea (L.) Mill.) stand with hemlock looper (Lambdina fiscellaria (Guen.)) defoliation, two balsam woolly adelgid (Adelges piceae (Ratz.)) infested balsam fir stands (thinned and unthinned sites), a balsam fir sawfly (Neodiprion abietis Harris) defoliated balsam fir stand, and an artificially defoliated black spruce stand. Roots of fir and spruce trees were inoculated with two isolates of A. ostoyae and re-examined after 2 years. The purpose of this study was to compare differences in root infection within plots for different types of host stress to examine the response of trees to controlled inoculations of A. ostoyae. There was a statistically significant difference in number of infected roots between the two isolates used as inoculum. There was significantly more root response with severity of infection within all sites except both adelgid plots. A marginally significant relationship between tree health and root infection was present in the balsam fir sawfly plot. There was a significantly larger number of infected roots associated with rhizomorphs in the naturally regenerated black spruce stand and the artificially defoliated balsam fir stand. These results suggest that stress prediposes the host tree to root infection by A. ostoyae.
Restricted
The association of caveolae, actin, and the dystrophin-glycoprotein complex: a role in smooth muscle phenotype and function?
(2005-10-31) Halayko, AJ; Stelmack, GL
Smooth muscle cells exhibit phenotypic and mechanical plasticity. During maturation, signalling pathways controlling actin dynamics modulate contractile apparatus-associated gene transcription and contractile apparatus remodelling resulting from length change. Differentiated myocytes accumulate abundant caveolae that evolve from the structural association of lipid rafts with caveolin-1, a protein with domains that confer unique functional properties. Caveolae and caveolin-1 modulate and participate in receptor-mediated signalling, and thus contribute to functional diversity of phenotypically similar myocytes. In mature smooth muscle, caveolae are partitioned into discrete linear domains aligned with structural proteins that tether actin to the extracellular matrix. Caveolin-1 binds with beta-dystroglycan, a subunit of the dystrophin glycoprotein complex (DGC), and with filamin, an actin binding protein that organizes cortical actin, to which integrins and focal adhesion complexes are anchored. The DGC is linked to the actin cytoskeleton by a dystrophin subunit and is a receptor for extracellular laminin. Thus, caveolae and caveolin-associated signalling proteins and receptors are linked via structural proteins to a dynamic filamentous actin network. Despite development of transgenic models to investigate caveolins and membrane-associated actin-linking proteins in skeletal and cardiac muscle function, only superficial understanding of this association in smooth muscle phenotype and function has emerged.
Restricted
Attenuation of the serotonin-induced increase in intracellular calcium in rat aortic smooth muscle cells by sarpogrelate
(2003-11-30) Saini, HK; Sharma, SK; Zahradka, P; Kumamoto, H; Takeda, N; Dhalla, NS
Although serotonin (5-HT) induced proliferation of vascular smooth muscle cells is considered to involve changes in intracellular Ca2+ ([Ca2+](i)), the mechanism of Ca2+ mobilization by 5-HT is not well defined. In this study, we examined the effect of 5-HT on rat aortic smooth muscle cells (RASMCs) by Fura-2 microfluorometry for [Ca2+](i) measurements. 5-HT was observed to increase the [Ca2+](i) in a concentration- and time-dependent manner. This action of 5-HT was dependent upon the extracellular concentration of Ca2+ ([Ca2+](e)) and was inhibited by both Ca2+ channel antagonists (verapamil and diltiazem) and inhibitors of sarcoplasmic reticular Ca2+ pumps (thapsigargin and cyclopiazonic acid). The 5-HT-induced increase in [Ca2+](i) was blocked by sarpogrelate, a 5-HT2A-receptor antagonist, but not by different agents known to block other receptor sites. 5-HT-receptor antagonists such as ketanserin, cinanserin, and mianserin, unlike methysergide, were also found to inhibit the 5-HT-induced Ca2+ mobilization, but these agents were less effective in comparison to sarpogrelate. On the other hand, the increase in [Ca2+](i) in RASMCs by ATP, angiotensin II, endothelin-1, or phorbol ester was not affected by sarpogrelate. These results indicate that Ca2+ mobilization in RASMCs by 5-HT is mediated through the activation of 5-HT2A receptors and support the view that the 5-HT-induced increase in [Ca2+](i) involves both the extracellular and intracellular sources of Ca2+.
Restricted
Bandwidth enhancement and size reduction of microstrip slot antennas
(2005-03-31T12:48:44Z) Latif, SI; Shafai, L; Sharma, SK
Reduced size microstrip monopole slot antennas with different slot shapes-straight, L and inverted T, and placed on a small ground plane, are investigated. The ground plane size is 50 mm x 80 mm, which is about the size of a typical PC Wireless card. Detailed simulation and experimental investigations are conducted to understand their behavior and optimize for broad-band operation. It is shown that, the variation in the slot shape, from straight to L and T shapes, helps in generating additional resonances, which when coupled to the original resonances of the slot, further increases impedance bandwidths. The bent shapes of the L and T slots reduce their height and provide more space on the ground plane for electronics. A mirror image dual L-slot antenna, placed at two adjacent corners of the ground plane, is also investigated and optimized for the polarization diversity. They provide an impedance bandwidth of 87 %, with near orthogonal radiation characteristics. The measured impedance bandwidths (S-11 = -10 dB) of up to 60%, 84%, and 80% are achieved for these straight, L and inverted T slots respectively, by suitably selecting their design parameters. The simulation results are in good agreement with the experimental data considering several practical issues.
Restricted
Beam focusing properties of circular monopole array antenna on a finite ground plane
(2005-10-31) Sharma, SK; Shafai, L
This paper presents the investigation results on the beam focusing properties of a wire circular monopole array (CMA) antenna consisting of six-elements on a finite ground plane, by exciting more than one monopole at a time. The excitation of more than one element provides enhanced horizontal and vertical plane peak directivities, and a reduced 3 dB beamwidth for the horizontal pattern. The effect of varying the number of monopole elements in the array is also discussed, when only one element is excited, and the remaining ones are shorted to the ground. The antenna was fabricated and tested for its impedance and radiation characteristics for one of the excitation schemes, and the results were found in reasonable agreement with the simulations.
Restricted
Bed-load transport model based on fractional size distribution
(2006-01-06T16:09:18Z) Ashiq, M; Doering, JC; Hosoda, T
Two models based on the fractional size distribution approach, used in conjunction with the excess discharge theory, have been developed by using bed-load data collected from the Roaring River (Rocky Mountain National Park, Colorado) during the summer of 1995. The first model is based on the critical discharge value of individual fractional (IF) sizes, IF model (for log-normal and nonlog-normal size distribution modes), while the other is based on critical discharge value for total (combined) sizes, total fractional (TF) sizes model (for log-normal and nonlog-normal size distribution modes). The performance of the log-normal size distribution based models was tested with data from the Roaring River, Rich Creek, and Fourmile Creek (three Colorado streams), whereas the performance of the nonlog-normal size distribution based models was tested using Pitzbach River data. The performance of the models was also tested by comparing their results with the Inpasihardjo fractional size distribution based model. For all tests, the TF model performed better for both the log-normal and nonlog-normal grain size distributions.Key words: fractional size, critical discharge, IF model, TF model, discharge theory, Roaring River.
Restricted
BLDC motor and drive conducted RFI simulation for automotive applications
(2003-05-31) Makaran, JE; LoVetri, J
In considering automotive conducted radio-frequency-interference (RFI) specifications applicable to motors and their associated drives, simulation of conducted RF emissions in the range from 150 kHz to 30 MHz is an area of interest from the product design perspective for several reasons. Traditionally, suppression of conducted noise in this frequency range of interest has been achieved through the use of bulk suppression elements such as capacitors and inductors. These elements consume valuable space within the motor, as well as add cost. The selection of bulk noise suppression elements, has, in the past, been predominately made through trial and error "brute force" methods. A method is presented whereby conducted RFI emissions can be simulated through the use of a high-fidelity virtual motor and drive model, as well as a virtual spectrum analyzer. Experimental validation of the model shows that accurate predictions can be made in the low-frequency range, below 10 MHz. Suggestions are made on how to improve the model at higher frequencies.
Restricted
Call admission control for QoS provisioning in 4G wireless networks: Issues and approaches
(2005-10-31T12:20:18Z) Niyato, D; Hossain, E
This article presents a survey on the issues and the approaches related to designing call admission control schemes for fourth-generation wireless systems. We review the state of the art of CAC algorithms used in the traditional wireless networks. The major challenges in designing the CAC schemes for 4G wireless networks are identified. These challenges are mainly due to heterogeneous wireless access environments, provisioning of quality of service to multiple types of applications with different requirements, provisioning for adaptive bandwidth allocation, consideration of both call-level and packet-level performance measures, and consideration of QoS at both the air interface and the wired Internet. To this end, architecture of a two-tier CAC scheme for a differentiated services cellular wireless network is presented. The proposed CAC architecture is based on the call-level and packet-level QoS considerations at both the wireless and wired parts of the network. A performance analysis model for an example CAC scheme based on this architecture is outlined, and typical numerical results are presented.
Restricted
Call-level and packet-level quality of service and user utility in rate-adaptive cellular CDMA networks: A queuing analysis
(2006-12-31T12:31:56Z) Niyato, D; Hossain, E
A queuing analytical model is presented to evaluate call-level and packet-level quality of service (QoS) metrics in the uplink of a voice/data cellular code division multiple access ( CDMA) network. In this model, a threshold-based call admission control (CAC) is used to limit the number of admitted calls in a cell and also to prioritize handoff calls over new calls. The transmission rates for data calls can be adjusted to accommodate more voice and/or data calls while satisfying the minimum signal-to-interference ratio (SIR)/ transmission rate requirement. Also, automatic repeat request (ARQ)-based error control is used for improved reliability of data packets. Call-level performance measures for both voice and data calls and packet-level performance measures specifically for data calls can be obtained from the analytical model. The interdependencies among call-level and packet-level QoS metrics are investigated under different CAC, rate adaptation, and error control parameter settings. To this end, the level of users' satisfaction ( or user utility) is formulated as a function of the QoS metrics and an optimization formulation is presented to obtain the local-optimal system parameters.
Restricted
A centralized TDMA-based scheme for fair bandwidth allocation in wireless IP networks
(2001-11-30T12:36:29Z) Hossain, E; Bhargava, VK
A unified time-division multiple access (TDMA)based centralized wireless access scheme is proposed for performing the statistical multiplexing of bursty data sources in a wireless packet data network. This scheme combines dynamic bandwidth allocation with admission control and packet conditioning (at the mobile stations) to provide fair bandwidth distribution among bursty data flows with different profile rates (or subscription levels) in an error-prone environment. The dynamic bandwidth allocation policy is credit-based and both the burst-level and the packet-level bandwidth allocations are considered. The performance of the scheme is evaluated using computer simulations for different total subscription levels, for different compositions of flows with different profile rates, and for different channel quality with different channel-error correlation patterns. The simulation results show that the throughput variability among flows with the same level of subscription is considerably small except for long range dependent flows with very high traffic burstiness. The relative throughput fairness among flows with different profile rates can also be achieved. The post facto loss and delay values (i.e., observed average packet delay and average packet loss values) for the flows depend on the corresponding delay tolerance limits of the data bursts, TDMA frame-length, and the wireless link utilization level. The energy efficiency of the wireless access scheme is evaluated in terms of the average transmitter usage time and the average receiver usage time in the mobile stations for both the burst-level and the packet-level bandwidth allocation. The proposed scheme can be used in an adaptive quality-of-service (QoS) framework for dynamically adjusting the QoS for flows in order to accommodate wireless channel errors and user mobility.