Photobleaching of optical absorption bands in the 5 eV region and the creation of others at higher and lower energy have been examined in the case of ArF (6.4 eV) and KrF (5 eV) excimer laserirradiation of 3GeO2:97SiO2glasses. We report a difference in the transformation process of the neutral oxygen monovacancy and also of the germanium lone pair center (GLPC) into electron trap centers associated with fourfold coordinated Ge ions and Ge-E′ centers when we use one or the other laser. Correlations between absorption bands and electron spin resonance signals were made after different steps of laser irradiation. It was found that the KrF laser generates twice as many Ge-E′ centers as the ArF laser for the same dose of energy delivered. The main reason for this difference is found to be the more efficient bleaching of the GLPC (5.14 eV) by the KrF laser compared to that by the ArF laser.
Silica-based thin-film multilayers are investigated as a means to enhance the effective second-order nonlinearity induced in silica glass structures by corona poling. Structures consisting of phosphorus-doped and undoped silica glass layers exhibit second harmonic generation (SHG) that is higher by an order of magnitude compared to the SHG in bulk silica glass poled under the same conditions. When the poled structure consists of two multilayered stacks separated in space, the stacks exhibit comparable poling-induced nonlinearities. This result suggests that the poling voltage is divided between the two stacks such that simultaneous poling of multiple regions within the sample is realized.
Samples of synthetic fused silica have been implanted at room temperature with silicon ions of energy 1.5 MeV. Fluences ranged from 1011 to 1013 cm−2. Samples were probed using variable‐energy positron annihilation spectroscopy. The Doppler‐broadening S parameter corresponding to the implanted region decreased with increasing fluence and saturated at a fluence of 1013 cm−2. It is shown that the decrease in the S parameter is due to the suppression of positronium (Ps) which is formed in the preimplanted material, due to the competing process of implantation‐induced trapping of positrons. In order to satisfactorily model the positron data it was necessary to account for positron trapping due to defects created by both electronic and nuclear stopping of the implanted ions. Annealing of the 1013 cm−2 sample resulted in measurable recovery of the preimplanted S parameter spectrum at 350 °C and complete recovery to the preimplanted condition at 600 °C. Volume compaction was also observed afterimplantation. Upon annealing, the compaction was seen to decrease by 75%.
The effective indices of the cladding modes of optical fibers depend on the refractive index of the medium surrounding the fiber. We show experimentally and theoretically that while cladding modes with similar effective indices normally have similar refractometric sensitivities, the addition of a 50 nm thick gold sheath enhances the sensitivity of some EH modes by more than one order of magnitude while nearly completely suppressing the sensitivity of neighbouring HE modes (by three orders of magnitude, down to insignificant levels). A differential sensitivity of ∼1000 nm/(refractive index unit) is experimentally reported between adjacent EH and HE grating resonances.
A photolithographic method is described for fabricating refractive index Bragg gratings in photosensitive optical fiber by using a special phase mask grating made of silica glass. A KrF excimer laser beam (249 nm) at normal incidence is modulated spatially by the phase mask grating. The diffracted light, which forms a periodic, high-contrast intensity pattern with half the phase mask grating pitch, photoimprints a refractive index modulation into the core of photosensitive fiber placed behind, in proximity, and parallel, to the mask; the phase mask grating striations are oriented normal to the fiber axis. This method of fabricating in-fiber Bragg gratings is flexible, simple to use, results in reduced mechanical sensitivity of the grating writing apparatus and is functional even with low spatial and temporal coherence laser sources.
Anomaly detection involves identifying observations that deviate from the normal behavior of a system. One of the ways to achieve this is by identifying the phenomena that characterize "normal" observations. Subsequently, based on the characteristics of data learned from the normal observations, new observations are classified as being either normal or not. Most state-of-the-art approaches, especially those which belong to the family parameterized statistical schemes, work under the assumption that the underlying distributions of the observations are stationary. That is, they assume that the distributions that are learned during the training (or learning) phase, though unknown, are not time-varying. They further assume that the same distributions are relevant even as new observations are encountered. Although such a " stationarity" assumption is relevant for many applications, there are some anomaly detection problems where stationarity cannot be assumed. For example, in network monitoring, the patterns which are learned to represent normal behavior may change over time due to several factors such as network infrastructure expansion, new services, growth of user population, etc. Similarly, in meteorology, identifying anomalous temperature patterns involves taking into account seasonal changes of normal observations. Detecting anomalies or outliers under these circumstances introduces several challenges. Indeed, the ability to adapt to changes in non-stationary environments is necessary so that anomalous observations can be identified even with changes in what would otherwise be classified as normal behavior. In this paper, we proposed to apply weak estimation theory for anomaly detection in dynamic environments. In particular, we apply this theory to detect anomaly activities in system calls. Our experimental results demonstrate that our proposal is both feasible and effective for the detection of such anomalous activities.
The observation of four-wave mixing (FWM) in single-walled carbon nanotubes (SWCNTs) deposited around a tilted fiber Bragg grating (TFBG) has been demonstrated. A thin, floating SWCNT film is manually wrapped around the outer cladding of the fiber and FWM occurs between two core-guided laser signals by TFBG-induced interaction of the core mode and cladding modes. The effective nonlinear coefficient is calculated to be 1.8 10 3W -1Km -1. The wavelength of generated idlers is tunable with a range of 7.8 nm.
We report on the fabrication of a chirped, phase mask that was used to create a fiber Bragg grating(FBG)device for the compensation of chromatic dispersion in longhaul optical transmission networks.Electron beamlithography was used to expose the grating onto a resist-coated quartz plate. After etching, this phase mask was used to holographically expose an index grating into the fiber core [K. O. Hill, F. Bilodeau, D. C. Johnson, and J. Albert, Appl. Phys. Lett.62, 1035 (1993)]. The linear increase in the grating period, “chirp,” is only 0.55 nm over the 10 cm grating. This is too small to be defined by computer aided design and a digital deflection system. Instead, the chirp was incorporated by repeatedly rescaling the analog electronics used for field size calibration. Special attention must be paid to minimize any field stitching and exposure artifacts. This was done by using overlapping fields in a “voting” method. As a result, each grating line is exposed by the accumulation of three overlapping exposures at 1/3 dose. This translates any abrupt stitching error into a small but uniform change in the line-to-space ratio of the grating. The phase mask was used with the double-exposure photoprinting technique [K. O. Hill, F. Bilodeau, B. Malo, T. Kitagawa, S. Thériault, D. C. Johnson, J. Albert, and K. Takiguchi, Opt. Lett. 19, 1314 (1994)]: a KrF excimer laser holographically imprints an apodized chirped Bragg grating in a hydrogen loaded SMF-28 optical fiber. Our experiments have demonstrated a spectral delay of −1311 ps/nm with a linearity of +/−10 ps over the 3 dB bandwidth of the resonant wavelength of the FBG. The reflectance, centered on 1550 nm, shows a side-lobe suppression of −25 dB. Fabrication processes and optical characterization will be discussed.
This paper presents ObjRecombGA, a genetic algorithm framework for recombining related programs at the object file level. A genetic algorithm guides the selection of object files, while a robust link resolver allows working program binaries to be produced from the object files derived from two ancestor programs. Tests on compiled C programs, including a simple web browser and a well-known 3D video game, show that functional program variants can be created that exhibit key features of both ancestor programs. This work illustrates the feasibility of applying evolutionary techniques directly to commodity applications. Copyright 2010 ACM.
The underlying issues relating to the usability and security of multiple passwords are largely unexplored. However, we know that people generally have difficulty remembering multiple passwords. This reduces security since users reuse the same password for different systems or reveal other passwords as they try to log in. We report on a laboratory study comparing recall of multiple text passwords with recall of multiple click-based graphical passwords. In a one-hour session (short-term), we found that participants in the graphical password condition coped significantly better than those in the text password condition. In particular, they made fewer errors when recalling their passwords, did not resort to creating passwords directly related to account names, and did not use similar passwords across multiple accounts. After two weeks, participants in the two conditions had recall success rates that were not statistically different from each other, but those with text passwords made more recall errors than participants with graphical passwords. In our study, click-based graphical passwords were significantly less susceptible to multiple password interference in the short-term, while having comparable usability to text passwords in most other respects. Copyright 2009 ACM.
Online systems often struggle to account for the complicated self-presentation and disclosure needs of those with complex identities or specialized anonymity. Using the lenses of gender, recovery, and performance, our proposed panel explores the tensions that emerge when the richness and complexity of individual personalities and subjectivities run up against design norms that imagine identity as simplistic or one-dimensional. These models of identity not only limit the ways individuals can express their own identities, but also establish norms for other users about what to expect, causing further issues when the inevitable dislocations do occur. We discuss the challenges in translating identity into these systems, and how this is further marred by technical requirements and normative logics that structure cultures and practices of databases, algorithms and computer programming.
Developing applications for touch devices is hard. Developing touch based applications for multi-user input is harder. The Multi-Touch for Java (MT4j) toolkit supports developing touch based applications for multiple users. In this paper, we outline our experience using MT4j for developing a number of software applications to support developers working in co-located teams. Our experience using the toolkit will help developers to understand the nuances of the toolkit and design issues that can be applied to other toolkits for developing multi-user touch based applications.
Germanium ions have been implanted in fused silica using ion beams having energies of 3 and 5 MeV and doses ranging from 1×1012 to 5×1014 ions/cm2. For wavelengths shorter than 400 nm, the optical absorption increases strongly with two absorption bands appearing at 244 and 212 nm. The ion-induced optical absorption can be bleached almost completely by irradiation with 249 nm excimer laser light. Ion implantation also increases the refractive index of silica near the substrate surface. At 632.8 nm a refractive index increase of more than 10-2 has been measured. This decreases by 4×10-3 upon bleaching with 249 nm light.
We have studied optical changes induced by ArF (6.4 eV/193 nm) excimer laser light illumination of high purity SiO2 implanted with Si2+ (5 MeV) at a fluence of 1015 ions/cm2. Optical absorption was measured from 3 eV (400 nm) to 8 eV (155 nm) and showed evidence of several well-defined absorption bands. A correlation in the bleaching behavior appears to exist between the so-called D band (located at 7.15 eV) and the well-known B2α band which is attributed to oxygen vacancies. Changes in the refractive index as a function of ArF illumination were measured and found to be in good quantitative agreement with a Kramers-Kronig analysis of the optical absorption data.
A two-step double ion-exchange process is employed to produce dual-core waveguides in glass. First, potassium ion exchange is carried out at 400°C. Then, silver ion exchange is performed at 300°C. The fabricated waveguides have low losses, large single-mode regions, and more symmetrical profiles than single ion-exchanged waveguides. Etched gratings are also made in dual-core waveguides. Very high efficiencies are demonstrated in these waveguides.
A fiber twist sensor based on the surface plasmon resonance (SPR) effect of an Au-coated tilted fiber Bragg grating (TFBG) is proposed. The SPR response to the twist effect on an Au-coated TFBG (immersing in distilled water) is studied theoretically and experimentally. The results show that the transmission power around the wavelength of SPR changes with the twist angle. For the twist ranging from 0° to 180° in clockwise or anti-clockwise directions, the proposed sensor shows sensitivities of 0.037 dBm/° (S-polarized) and 0.039 dBm/° (P-polarized), which are almost 7.5 times higher than that of the current similar existing twist sensor.
Phosphate glass samples doped with silver ions through a Na+-Ag+ ion-exchange process were treated in a hydrogen atmosphere at temperatures near 430 °C for durations ranging from 4 to 5 h. Such treatment causes metallic silver precipitation at the surface as well as nanoclustering of silver atoms under the surface under conditions very similar to those used for silicate glasses. The presence of silver clusters resulted in a characteristic coloring of the glass and was verified by the observation of a plasmon resonance peak near 410-420 nm in the absorption spectra. Applying a DC voltage between 1.4 and 2 kV at temperatures between 120 and 130 °C led to dissolution of the clusters in the area under the positive electrode, thereby bleaching the glass color. The use of a patterned doped-silicon electrode further led to the formation of a 300 nm thick surface relief on the glass surface and of a volume complex permittivity grating extending at least 4 μm under the surface. Such volume complex refractive index gratings may find applications in passive or active (laser) photonic devices in rare-earth doped phosphate glasses, where conventional bulk grating formation techniques have limited applicability.
The aeronautics industry is looking for ice protection systems consuming less energy. Electromechanical and especially piezoelectric solutions are a promising area of research for reducing average consumptions. This article provides an analytical model
of a simple structure to assess the power and voltage required to obtain the delamination of the accumulated layer of ice at the support/ice interface. This model also allows analyzing the impact of the resonance frequencies used for supplying piezoelectric actuators on the tensile stress into PZT materials. Finally, this article assesses the effect of different ice
- phobic coatings combined with piezoelectric ice protection systems.
Experimental measurements of ice adhesion for different ice - phobic coatings allow evaluating the shear stress at which ice is detached from the surface. These results are then used to estimate - thanks to the proposed analytical model
- the additional gain of power that would be provided by the use of such coatings.
A variable diffraction efficiency phase mask is produced by focused ion beam, implanting a grating pattern into a fused SiO
2 substrate with a 100-nm-diam, 200keV Si beam. The substrate is prepared by cleaning and coating with a 20-nm-thick film of Al to dissipate the ion charge. The pattern consists of 930 lines, each 80μm long, at a pitch of 1.075μm, to obtain a 1-mm-long grating. The substrate is wet etched in a 1M% HF solution for about 45min to produce a phase mask with the desired diffraction efficiency. This phase mask is used to photoimprint Bragg gratings into standard hydrogenated single-mode telecommunication fibers using 193nm light from an ArF laser.
Frost cracking, the breakdown of rock by freezing, is one of the most important mechanical weathering processes acting on Earth's surface. Insights on the mechanisms driving frost cracking stem mainly from laboratory and theoretical studies. Transferring insights from such studies to natural conditions, involving jointed bedrock and heterogeneous thermal and hydrological properties, is a major challenge. We address this problem with simultaneous in situ measurements of acoustic emissions, used as proxy of rock damage, and rock temperature/moisture content. The 1 year data set acquired in an Alpine rock wall shows that (1) liquid water content has an important impact on freezing-induced rock damage, (2) sustained freezing can yield much stronger damage than repeated freeze-thaw cycling, and (3) that frost cracking occurs over the full range of temperatures measured extending from 0 down to -15°C. These new measurements yield a slightly different picture than previous field studies where ice segregation appears to play an important role. Key PointsRock liquid water content has an important impact on the freezing-induced damageSustained freezing can yield stronger damage than repeated freeze-thaw cyclingFrost cracking occurs on a wide range of temperatures extending from 0 to -15C
I examine the relation between sensation and discursive thought (dianoia) in Plato, Plotinus, and Proclus. In Theaetetus, a soul whose highest faculty was sensation would have no unified experience of the sensible world, lacking universal ideas to give order to the sensible flux. It is implied that such universals are grasped by the soul's thinking. In Plotinus the soul is not passive when it senses the world, but as the logos of all things it thinks the world through its own forms. Proclus argues against the derivation of universal logoi from the senses, which alone can't make the sensible world comprehensible. At most they give a record of the original sense-impression in its particularity. The soul's own projected logoi give the sensible world stability. For Proclus, bare sensation does not depend on thought, but a unified experience of the sense-world depends on its paradigmatic logoi in our souls.
The techno-economic feasibility of retrofitting existing Canadian houses with solar assisted heat pump (SAHP) is investigated. The SAHP architecture is adopted from previous studies conducted for the Canadian climate. The system utilizes two thermal storage tanks to store excess solar energy for use later in the day. The control strategy is defined in order to prioritise the use of solar energy for space and domestic hot water heating purposes. Due to economic and technical constraints a series of eligibility criteria are introduced for a house to qualify for the retrofit. A model was built in ESP-r and the retrofit was introduced into all eligible houses in the Canadian Hybrid Residential End-Use Energy and GHG Emissions model. Simulations were conducted for an entire year to estimate the annual energy savings, and GHG emission reductions. Results show that the SAHP system performance is strongly affected by climatic conditions, auxiliary energy sources and fuel mixture for electricity generation. Energy consumption and GHG emission of the Canadian housing stock can be reduced by about 20% if all eligible houses receive the SAHP system retrofit. Economic analysis indicates that the incentive measures will likely be necessary to promote the SAHP system in the Canadian residential market.
Buildings play a significant role in climate change mitigation. In North America, energy used to construct and operate buildings accounts for some 40% of total energy use, largely originating from fossil fuels. The strategic reduction of these energy demands requires knowledge of potential upgrades prior to a building's construction. Furthermore, renewable energy generation integrated into buildings façades and district systems can improve the resiliency of community infrastructure. However, loads that are non-coincidental with on-site generation can cause load balancing issues. This imbalance is typically due to solar resources peaking at noon, whereas building loads typically peak in the morning and late afternoon or evenings. Ideally, the combination of on-site generation and localized storage could remedy such load balancing issues while reducing the need for fossil fuels. In response to these issues, this paper contributes a methodology that co-optimizes building designs and district technologies as an integrated community energy system. A distributed evolutionary algorithm is proposed that can navigate over 10154 potential community permutations. This is the first time in literature that a methodology demonstrates the co-optimization of buildings and district energy systems to reduce energy use in buildings and balance loads at this scale. The proposed solution is reproducible and scalable for future community masterplanning studies.
This study was conducted to assess the techno-economic feasibility of converting the Canadian housing stock (CHS) into net/near zero energy buildings by introducing and integrating high efficient and renewable/alternative energy technologies in new construction and existing houses. Performance assessment of energy retrofit and renewable/alternative energy technologies in existing houses in regional and national scale is necessary to devise feasible strategies and incentive measures. The Canadian Hybrid Residential End-Use Energy and GHG Emissions model (CHREM) that utilizes a bottom-up modeling approach is used to investigate the techno-economic feasibility of air to water heat pump retrofit in the Canadian housing stock. The proposed energy retrofit includes an air to water heat pump, auxiliary boiler, thermal storage tank, hydronic heat delivery and domestic hot water (DHW) heating. Energy savings, GHG emission changes and economic feasibility of the air source heat pump retrofit are considered in this study. Results show that there is a potential to reduce 36% of energy consumption and 23% of GHG emissions of the CHS if all eligible houses undertake the retrofit. Economic analysis indicates that the feasibility of air to water heat pump systems is strongly affected by the current status of primary energy use for electricity generation and space and DHW heating as well as energy prices and economic conditions. Legislation, economic incentives and education for homeowners are necessary to enhance the penetration level of air to water heat pump retrofits in the CHS.
An improved understanding of the consumption patterns, end-uses, and temporal variations of electrical loads in houses is warranted because a significant fraction of a society's total electricity consumption occurs within residential buildings. In general, there is a lack of high-temporal-resolution data describing occupant electrical consumption that are available to researchers in this field. To address this, new measurements were performed and combined with data emanating from an earlier study to provide a database of annual measurements for 23 houses at a 1-min resolution that characterizes whole-house, non-HVAC, air conditioner, and furnace fan electrical draws, as well as the draw patterns of some major appliances. All houses were located in Ottawa, Canada. The non-HVAC measurements of this 23-house sample were shown to be in agreement with published estimates for the housing stock. The furnace fan was found to be the most significant end-use. These high-temporal-resolution data of electrical demands in houses can be used by researchers to increase the fidelity of building performance simulation analyses of different micro-generation technologies in residential buildings.
Fuel cells with nominal outputs of approximately 1kW AC are emerging as a prime-mover of a micro-cogeneration system potentially well-suited to compete, on an energy basis, with conventional methods for satisfying occupant electrical and thermal demands in a residential application. As the energy benefits of these systems can be incremental when compared to efficient conventional methods, it is especially important to consider the uncertainties of the models on which simulation results are based. However, researchers have yet to take this aspect into account.This article makes a contribution by demonstrating how these model uncertainties may be propagated to the simulation results of a micro-cogeneration system for comparison to a reference scenario using a case study. This case study compares the energy performance of a fuel-cell based micro-cogeneration system serving only domestic hot water demands to an efficient reference scenario where the conventional methods for providing electrical and thermal demands are considered to be a central gas-fired combined-cycle plant and a condensing tankless water heater respectively. The simulation results demonstrated that if model uncertainties were ignored, it would have been possible to demonstrate that the considered micro-cogeneration system was more efficient than the reference scenario for average consumption levels of domestic hot water. However, when model uncertainties were considered, the efficiency of the considered micro-cogeneration system could not reliably exceed that of the reference scenario by serving the domestic hot water needs of a single-family home.
Oral narrative skills are assumed to develop through parent-child interactive routines. One such
routine is shared reading. A causal link between shared reading and narrative knowledge,
however, has not been clearly established. The present research tested whether an 8-week
shared-reading intervention enhanced the fictional narrative skills of children entering formal
education. Dialogic reading, a shared reading activity that involves elaborative questioning
techniques, was used to engage children in oral interaction during reading and to emphasize
elements of story knowledge. Forty English-speaking five- and six-year-olds were assigned to
either the dialogic-reading or an alternative-treatment group. ANCOVA results found that the
dialogic-reading children’s post-test narratives were significantly better on structure and context
measures than those for the alternative-treatment children, but results differed for produced or
retold narratives. The dialogic-reading children also showed expressive vocabulary gains.
Overall, this study concretely determined that aspects of fictional narrative construction
knowledge can be learned from interactive book reading.
Techno-economic impact of retrofitting houses in the Canadian housing stock with PV and BIPV/T systems is evaluated using the Canadian Hybrid End-use Energy and Emission Model. Houses with south, south-east and south-west facing roofs are considered eligible for the retrofit since solar irradiation is maximum on south facing surfaces in the northern hemisphere. The PV system is used to produce electricity and supply the electrical demand of the house, with the excess electricity sold to the grid in a net-metering arrangement. The BIPV/T system produces electricity as well as thermal energy to supply the electrical as well as the thermal demands for space and domestic hot water heating. The PV system consists of PV panels installed on the available roof surface while the BIPV/T system adds a heat pump, thermal storage tank, auxiliary heater, domestic hot water heating equipment and hydronic heat delivery system, and replaces the existing heating system in eligible houses. The study predicts the energy savings, GHG emission reductions and tolerable capital costs for regions across Canada. Results indicate that the PV system retrofit yields 3% energy savings and 5% GHG emission reduction, while the BIPV/T system yields 18% energy savings and 17% GHG emission reduction in the Canadian housing stock. While the annual electricity use slightly increases, the fossil fuel use of the eligible houses substantially decreases due to BIPV/T system retrofit.
It has been observed in the literature that as the cardinality of the prescribed discrete input-output data set increases, the corresponding four-bar linkages that minimise the Euclidean norm of the design and structural errors tend to converge to the same linkage. The important implication is that minimising the Euclidean norm, or any p-norm, of the structural error, which leads to a nonlinear least-squares problem requiring iterative solutions, can be accomplished implicitly by minimising that of the design error, which leads to a linear least-squares problem that can be solved directly. Apropos, the goal of this paper is to take the first step towards proving that as the cardinality of the data set tends towards infinity the observation is indeed true. In this paper we will integrate the synthesis equations in the range between minimum and maximum input values, thereby reposing the discrete approximate synthesis problem as a continuous one. Moreover, we will prove that a lower bound of the Euclidean norm, and indeed of any p-norm, of the design error for planar RRRR function-generating linkages exists and is attained with continuous approximate synthesis.
Building Performance Simulation (BPS) is a powerful tool to estimate and reduce building energy consumption at the design stage. However, the true potential of BPS remains unrealized if trial and error simulation methods are practiced to identify combinations of parameters to reduce energy use of design alternatives. Optimization algorithms coupled with BPS is a process-orientated tool which identifies optimal building configurations using conflicting performance indicators. However, the application of optimization approaches to building design is not common practice due to time and computation requirements. This paper proposes a hybrid evolutionary algorithm which uses information gained during previous simulations to expedite and improve algorithm convergence using targeted deterministic searches. This technique is applied to a net-zero energy home case study to optimize trade-offs in passive solar gains and active solar generation using a cost constraint.
We describe a novel Distributed Storage protocol in Disruption (Delay) Tolerant Networks (DTN). Since DTNs can not guarantee the connectivity of the network all the time, distributed data storage and look up has to be performed in a store-and-forward way. In this work, we define local distributed location regions which are called cells to facilitate the data storage and look up process. Nodes in a cell have high probability of moving within their cells. Our protocol resorts to storing data items in cells which have hierarchical structure to reduce routing information storage at nodes. Multiple copies of a data item may be stored at nodes to counter the adverse impact of the nature of DTNs. The cells are relatively stable regions and as a result, data exchange overheads among nodes are reduced. Through experimentation, we show that the proposed distributed storage protocol achieves higher successful data storage ratios with lower delays and limited data item exchange requirements than other protocols in the literature.
we present a method of segmenting video to detect cuts with accuracy equal to or better than both histogram and other feature based methods. As well, the method is faster than other feature based methods. By utilizing feature tracking on corners, rather than lines, we are able to reliably detect features such as cuts, fades and salient frames. Experimental evidence shows that the method is able to withstand high motion situations better than existing methods. Initial implementations using full sized video frames are able to achieve processing rates of 10-30 frames per second depending on the level of motion and number of features being tracked; this includes the time to generate the MPEG decompressed frames.
The design and analysis of community-scale energy systems and incentives is a non-trivial task. The challenge of such undertakings is the well-documented uncertainty of building occupant behaviours. This is especially true in the residential sector, where occupants are given more freedom of activity compared to work environments. Further complicating matters is the dearth of available measured data. Building performance simulation tools are one approach to community energy analysis, however such tools often lack realistic models for occupant-driven demands, such as appliance and lighting (AL) loads. For community-scale analysis, such AL models must also be able to capture the temporal and inter-dwelling variation to achieve realistic estimates of aggregate electrical demand. This work adapts the existing Centre for Renewable Energy Systems Technology (CREST) residential energy model to simulate Canadian residential AL demands. The focus of the analysis is to determine if the daily, seasonal, and inter-dwelling variation of AL demands estimated by the CREST model is realistic. An in-sample validation is conducted on the model using 22 high-resolution measured AL demand profiles from dwellings located in Ottawa, Canada. The adapted CREST model is shown to broadly capture the variation of AL demand variations observed in the measured data, however seasonal variation in daily AL demand behaviour was found to be under-estimated by the model. The average and variance of daily load factors was found to be similar between measured and modelled. The model was found to under-predict the daily coincidence factors of aggregated demands, although the variance of coincident factors was shown to be similar between measured and modelled. A stochastic baseload input developed for this work was found to improve estimates of the magnitude and variation of both baseload and peak demands.
This article describes the progress made toward implementing Resource Description and Access (RDA) in libraries across Canada, as of Fall 2013. Differences in the training experiences in the English-speaking cataloging communities and French-speaking cataloging communities are discussed. Preliminary results of a survey of implementation in English-Canadian libraries are included as well as a summary of the support provided for French-Canadian libraries. Data analysis includes an examination of the rate of adoption in Canada by region and by sector. Challenges in RDA training delivery in a Canadian context are identified, as well as opportunities for improvement and expansion of RDA training in the future.
The rise of game development and game studies on university campuses prompts academic libraries to consider how to support teaching and research in this area. This article examines current issues and challenges in the development of game collections at academic libraries. The gaming ecosystem has become more complex and libraries may need to move beyond collections largely based on console video games. This article will advance the discussion by considering emerging issues to support access to the full range of games. The article will use examples from Carleton University Library, Ottawa, which has been developing a game collection since 2008.
An apodized in-fibre Bragg grating reflector is fabricated using the phase mask photoimprinting technique. The reflector has a centre wavelength of 1550 nm, a bandwidth of 0.22 nm and a peak reflectivity of 90%. At 0.4 nm (50 GHz) from the centre wavelength the reflectivity is 40 dB lower than the peak reflectivity; this is an improvement of more than 20 dB over an unapodized Bragg grating reflector with similar bandwidth and peak reflectivity.
Random Forests variable importance measures are often used to rank variables by their relevance to a classification problem and subsequently reduce the number of model inputs in high-dimensional data sets, thus increasing computational efficiency. However, as a result of the way that training data and predictor variables are randomly selected for use in constructing each tree and splitting each node, it is also well known that if too few trees are generated, variable importance rankings tend to differ between model runs. In this letter, we characterize the effect of the number of trees (ntree) and class separability on the stability of variable importance rankings and develop a systematic approach to define the number of model runs and/or trees required to achieve stability in variable importance measures. Results demonstrate that both a large ntree for a single model run, or averaged values across multiple model runs with fewer trees, are sufficient for achieving stable mean importance values. While the latter is far more computationally efficient, both the methods tend to lead to the same ranking of variables. Moreover, the optimal number of model runs differs depending on the separability of classes. Recommendations are made to users regarding how to determine the number of model runs and/or trees that are required to achieve stable variable importance rankings.
An apodized chirped in-fibre Bragg grating that has a linear dispersion characteristic is reported. The frequency components of an optical pulse (centre wavelength 1551 nm; 10 GHz bandwidth) incident on the grating are reflected with a relative delay that varies linearly from 0 to 130 ps across the spectral width of the pulse. The dispersion compensator is used to correct for the dispersion in a 100 km link (nondispersion shifted fibre) operating at a 10 Gbit/s transmission rate and a wavelength of 1551 nm.
When hydrogen loading is used to enhance the photosensitivity of silica-based optical waveguides and fibres, the presence of molecular hydrogen dissolved in the glass matrix changes the effective index of propagation of guided optical modes by as much as 0.05%. Real-time monitoring of the reflectivity spectrum of Bragg gratings written in such conditions shows that the centre wavelength follows the changes in hydrogen concentration due to diffusion and reaction with glass defects.