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Using building performance simulation for fault impact evaluation
No full textAutomated building fault detection and diagnostics (AFDD) has become a valuable tool to maintain the efficiency of high-performance buildings. Still, when faults are detected or diagnosed, they are often presented to the building operators as-is with little explanation of their potential impacts. This could lead to higher workload and knowledge requirement for the operators to assess the situation and schedule maintenance tasks. One approach to aid the building operators' decision-making process is to provide quantitative impact metrics for faults. Metrics such as energy, thermal comfort, and cost can be simulated using building performance simulation (BPS) software or data-driven models. While BPS has been used in fault detection research as well as advanced control algorithms, little work has done to introduce BPS to fault evaluation and fault management applications. This paper proposes a standardized procedure to use BPS to evaluate diagnosed faults in building systems by quantifying symptoms caused by faults, and then translate these symptoms to BPS inputs. This research tries to tackle the challenges of uncertainties caused by parameter estimation and providing strategies to symptoms that cannot be directly translated to a BPS input. The proposed method can be generalized to be integrated with existing FDD tools or future FDD research.Peer reviewed: YesNRC publication: Ye
New insights into the nature of transition disks from a complete disk survey of the Lupus star-forming region
No full textTransition disks with large dust cavities around young stars are promising targets for studying planet formation. Previous studies have revealed the presence of gas cavities inside the dust cavities hinting at recently formed, giant planets. However, many of these studies are biased towards the brightest disks in the nearby star forming regions, and it is not possible to derive reliable statistics that can be compared with exoplanet populations. We present the analysis of 11 transition disks with large cavities (>20 AU radius) from a complete disk survey of the Lupus star forming region, using ALMA Band 7 observations at 0.3" (22-30 AU radius) resolution of the 345 GHz continuum, 13CO and C18O 3-2 observations and the Spectral Energy Distribution of each source. Gas and dust surface density profiles are derived using the physical-chemical modeling code DALI. This is the first study of transition disks of large cavities within a complete disk survey within a star forming region. The dust cavity sizes range from 20-90 AU radius and in three cases, a gas cavity is resolved as well. The deep drops in gas density and large dust cavity sizes are consistent with clearing by giant planets. The fraction of transition disks with large cavities in Lupus is ~11%, which is inconsistent with exoplanet population studies of giant planets at wide orbits. Furthermore, we present a hypothesis of an evolutionary path for large massive disks evolving into transition disks with large cavities.Peer reviewed: YesNRC publication: Ye
Dust growth and dust trapping in protoplanetary disks
No full textALMA has revolutionized our view of protoplanetary disks, revealing structures such as gaps, rings and asymmetries that indicate dust trapping as an important mechanism in the planet formation process. However, the high resolution images have also shown that the optically thin assumption for millimeter continuum emission may not be valid and the low values of the spectral index may be related to optical depth rather than dust growth. Longer wavelength observations are essential to properly disentangle these effects. The high sensitivity and spatial resolution of the next-generation Very Large Array (ngVLA) will open up the possibilities to spatially resolve disk continuum emission at centimeter wavelengths and beyond, which allows the study of dust growth in disks in the optically thin regime and further constrain models of planet formation.Peer reviewed: NoNRC publication: Ye
Emission from strained germanium nanocrystals
No full textWe analyse the intense photoluminescence (PL) observed at energies from 600 to 1500 meV for many molecular beam epitaxy grown Si1-xGex epitaxial layers. We show that the unexplained broad PL peak is due to self-assembled Ge nanocrystals (NCs) within the SiGe layers. The NCs are assumed lattice matched to the SiGe in the vertical, growth direction. As the Ge-fraction in the SiGe layer increases, the vertical strain in the NCs changes from compressive to tensile at x ~ 0.36, lowering the NC band gap (BG) below that of bulk Ge. We analyse PL results for 64 samples exhibiting this broad PL peak by examining how it follows the strained Ge BG for x from 0.05 to 0.53. The PL is resolvable as two narrower peaks separated by the TO phonon energy for Ge. Strain and confinement shifted NC bound exciton energies calculated numerically agree well with the measured ones.Peer reviewed: YesNRC publication: Ye
Extraction of cobalt and nickel from a pyrrhotite rich tailings sample via bioleaching
No full textThe growing use and acceptance of electric vehicles (EV), as evidenced by the record sales of over 750 thousand vehicles in 2016 and a current global EV stock of 2 million vehicles, is putting pressure on sourcing raw materials such as cobalt, and to a lesser extent, nickel. Global supply is poorly diversified, with 50\u201360% of global cobalt production sourced solely from the Democratic Republic of Congo (DRC). One potential source for cobalt and nickel are low-grade nickeliferous pyrrhotite tailings, of which 50\u2013100 million tonnes are present in the Sudbury area alone. This paper presents the extraction of cobalt and nickel from this material using a combination of flotation and bioleaching technologies. The findings of a high-level techno-economic analysis of the proposed processing flowsheet are presented.Peer reviewed: YesNRC publication: Ye
Mid-infrared suspended waveguide platform and building blocks
No full textPeer reviewed: YesNRC publication: Ye
Detection of thermal strain in steel rails with BOTDA
No full textRail transportation is one of the most important and efficient forms of transportation. Large thermal strain can develop in the rail steel due to extreme climatic conditions resulting in safety related issues. We carried out a thermal-strain monitoring test on the rail specimen over a large temperature range from -40 18 C to +50 18 C using a Brillouin optical time-domain analyzer (BOTDA) for the first time, to the best of our knowledge. Two jacketed fibers and small-diameter carbon/polyimide-coating single-mode fiber were used for the purpose of investigating the jacket effect of thermal-strain detection on the rail. Although a nonlinear response to the temperature of the loose jacketed fiber was found, it was applicable for thermal strain monitoring when glued on the surface of the rail sample. The measured thermal strain in the rail specimen was validated by the results obtained by the strain gauge. The thermally induced strain from the large rail specimen was found to have suppressed the nonlinear impact of the fiber jacket.Peer reviewed: YesNRC publication: Ye
Longitudinal strain monitoring of rails using distributed and discrete sensors
No full textWith one of the most extensive rail networks in the world (48,000 km of track), rail transportation is vital to Canada. Newer, more powerful locomotives hauling heavier freight at higher operating speeds are capable of producing twice the tractive effort of older locomotives. This has raised concerns regarding the risks associated with exceeding the longitudinal load carrying capacity of in-service rail support systems (e.g. bridges). There is now a growing need to investigate the longitudinal stresses that rails are being subjected to and to evaluate the potential requirement for rail rehabilitation. Past studies exploring structural health monitoring (SHM) techniques for rail infrastructure have focused on the application of discrete strain sensor technologies making it difficult to understand the rail\u2019s full strain profile under locomotive loading. This paper introduces a series of dynamic field tests conducted to assess the suitability of both distributed and discrete sensors to measure longitudinal rail strain under locomotive braking. A distributed fibre optic sensor based on Rayleigh backscatter in addition to adhesive and friction bonded foil strain gauges were used. Conclusions will be drawn as to the most applicable rail monitoring technology and future research directions will be outlined.Peer reviewed: NoNRC publication: Ye
Small-molecule allosteric triggers of Clostridium difficile toxin B auto-proteolysis as a therapeutic strategy
No full textClostridium difficile causes increasing numbers of life-threatening intestinal infections. Symptoms associated with C. difficile infection (CDI) are mediated by secreted protein toxins, whose virulence is modulated by intracellular auto-proteolysis following allosteric activation of their protease domains by inositol hexakisphosphate (IP6). Here, we explore the possibility of inactivating the C. difficile toxin B (TcdB) by triggering its auto-proteolysis in the gut lumen prior to cell uptake using gain-of-function small molecules. We anticipated that high calcium concentrations typically found in the gut would strongly chelate IP6, precluding it from pre-emptively inducing toxin auto-proteolysis if administered exogenously. We therefore designed IP6 analogs with reduced susceptibility to complexation by calcium, which maintained allosteric activity at physiological calcium concentrations. We found that oral administration of IP6 analogs attenuated inflammation and promoted survival in mouse models of CDI. Our data provide impetus to further develop small-molecule allosteric triggers of toxin auto-proteolysis as a therapeutic strategy.Peer reviewed: YesNRC publication: Ye