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Two sides of a coin： host-plant synchrony fitness trade-offs in the population dynamics of the western spruce budworm

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Insect Science 2018年第1期25卷 117-126页

作者： Jacques Regniere Vincent G. Nealis Natural Resources Canada Canadian Forest Service Laurentian Forestry Centre Quebec Canada Natural Resources Canada Canadian Forest Service Pacific Forestry Centre Victoria British Columbia Canada

Conifer-feeding budworms emerge from overwintering sites as small larvae in early spring, several days before budburst, and mine old needles. These early-emerging larvae suffer considerable mortality during this foraging period as they disperse in search of available, current-year buds. Once buds flush, surviving budworms construct feeding shelters and must complete maturation before fresh host foliage senesces and lignifies later in the summer. Late-developing larvae suffer greater mortality and survivors have lower fecundity when feeding on older foliage. Thus, there is a seasonal trade-off in fitness associated with host synchrony： early-emerging budworms have a greater risk of mortality during spring dispersal but gain better access to the most nutritious foliage, while, on the other hand, late-emerging larvae incur a lower risk during the initial foraging period but must contend with rapidly diminishing resource quality at the end of the feeding period. We investigate the balance that results from these early-season and late-season synchrony fitness trade-offs using the concept of the phenological window. Parameters associated with the variation in the phenological window are used to estimate generational fitness as a function of host-plant synchrony. Because defoliation modifies these relationships, it is also included in the analysis. We show that fitness trade-offs characterizing the phenological window result in a robust synchrony relationship between budworm and host plant over a wide geographic range in southern British Columbia, canada.

关键词： budburst budworm feeding fitness synchrony

Mixed graphite cast iron for automotive exhaust component applications

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China Foundry 2017年第6期14卷 519-524页

作者： De-lin Li Canmet MATERIALS Natural Resources CanadaHamiltonONCanada

Both spheroidal graphite iron and compacted graphite iron are used in the automotive industry. A recently proposed mixed graphite iron exhibits a microstructure between the conventional spheroidal graphite iron and compacted graphite iron. Evaluation results clearly indicate the suitability and benefits of mixed graphite iron for exhaust component applications with respect to casting, machining, mechanical, thermophysical, oxidation, and thermal fatigue properties. A new ASTM standard specification(A1095) has been created for compacted, mixed, and spheroidal graphite silicon-molybdenum iron castings. This paper attempts to outline the latest progress in mixed graphite iron published.

关键词： SiMo iron spheroidal graphite compacted graphite mixed graphite exhaust components brittleness at medium temperature thermal fatigue cycles

Impact Assessment and Mitigation Techniques for High Penetration Levels of Renewable Energy Sources in Distribution Networks:Voltage-control Perspective

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Journal of Modern Power Systems and Clean Energy 2022年第2期10卷 450-458页

作者： Ahmed S.A.Awad Dave Turcotte Tarek H.M.El-Fouly Natural Resources Canada Can-metENERGYVarennesCanadaon leave from the Electrical Power and Machines DepartmentFaculty of EngineeringAin Shams UniversityCairo 11566Egyp Natural Resources Canada CanmetENERGYVarennesCanada Advanced Power and Energy Center Khalifa UniversityAbu DhabiUnited Arab Emirates

The integration of renewable distributed generation(RDG)into distribution networks is promising and increasing nowadays.However,high penetration levels of distributed generation(DG)are often limited as they may have an adverse effect on the operation of distribution networks.One of the operation challenges is the interaction between DG and voltage-control equipment,e.g.,an under-load tap changer(ULTC),which is basically designed to compensate for voltage changes caused by slow load variations.The integration of variable DGs leads to rapid voltage fluctuations,which can negatively affect the tap operation of ULTC.This paper investigates the impact of high penetration levels of RDG on the tap operation of ULTC in distribution networks through simulations.Various mitigation techniques that can alleviate this impact are also examined.Among these techniques,constant power-factor mode is regarded as the best trade-off between the simplicity and effectiveness of minimizing the number of tap operations.Simulations are performed on a Canadian benchmark rural distribution feeder using OpenDSS software.

关键词： Renewable energy distributed generation(DG) voltage regulator load tap changer distribution network.

A simulation-based evaluation of the absolute and comparative approaches in a code compliance process from the energy use perspective: Cold-climate case study

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Building Simulation 2022年第8期15卷 1401-1418页

作者： Sara Gilani Alex Ferguson Meli Stylianou CanmetENERGY-Ottawa Natural Resources Canada1 Haanel DrOttawaON K1A 1M1Canada

Like many countries,canada's building code includes a performance compliance path that compares the energy use of a proposed design to that of a reference house.Today,provinces across canada are contemplating an alternative absolute energy use intensity approach.However,the effect of adopting the absolute approach on house design is not well understood.This study first developed a proof-of-concept methodology for a technical simulation-based comparison of the two approaches.Then,it performed a comparative analysis between the design outcomes of the two approaches using the developed methodology.To this end,statistically representative archetypes were configured to comply with the prescriptive requirements of the building code.Key characteristics of each archetype were then varied through parametric study,and the resulting energy performance under the absolute and comparative approaches were analyzed.The results of this study indicated that the two approaches had different effects on the design and energy use of houses in heating-dominated climate zones.Houses performing better under the absolute approach consumed less energy and exhibited more compact architectural form.These houses were also less sensitive to improvements in airtightness and envelope than houses performing better under the comparative approach.The results suggest that adopting the absolute approach based on the energy use intensity metric in building codes would encourage design and construction of houses with higher energy efficiency.

关键词： performance path energy efficiency absolute target percent better than code reference building archetype

A new method for generating a clear-sky Landsat composite for cropland from cloud-contaminated Landsat-7 and Landsat-8 images

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International Journal of Digital Earth 2018年第5期11卷 533-545页

作者： Junhua Li Shusen Wang canada Centre for Mapping and Earth Observation Natural Resources CanadaOttawaCanada

A new method was developed in this study for producing a clear-sky Landsat composite for cropland from cloud-contaminated Landsat images acquired in a short time period.It used Thiel–Sen regression to normalize all Landsat scenes to a MODIS image to make all Landsat images radiometrically consistent and comparable.Pixel selection criteria combining the modified maximum vegetation index and the modified minimum visible reflectance selection methods were designed to enhance the pixel selection of land/water over cloud/shadow in the image compositing.The advantages of the method include(1)avoiding complicated atmospheric corrections but with reliable surface reflectance results,(2)being insensitive to errors induced by image coregistration uncertainties between Landsat and MODIS images,(3)avoiding the lack of samples for the regression analysis using the full Landsat scenes(rather than overlay regions),and(4)enhancing cloud/shadow detection.The composite image has MODIS-like surface reflectance,thus making MODIS algorithms applicable for retrieving biophysical parameters.The method was automatically implemented on a set of 13 cloud-contaminated(>39%)Landsat-7(Scan-Line CorrectorOff)and Landsat-8 scenes acquired during peak growing season in a crop region of Manitoba,canada.The result was a 95.8%cloud-free image.The method can also substantially increase the usage of cloudcontaminated Landsat data.

关键词： Landsat compositing MODIS Thiel–Sen regression

Responses of jointed rock masses subjected to impact loading

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第4期10卷 624-634页

作者： Shabnam Aziznejad Kamran Esmaieli John Hadjigeorgiou Denis Labrie Lassonde Institute of Mining University of Toronto CanmetMINING Natural Resources Canada

Impact-induced damage to jointed rock masses has important consequences in various mining and civil engineering applications. This paper reports a numerical investigation to address the responses of jointed rock masses subjected to impact loading. It also focuses on the static and dynamic properties of an intact rock derived from a series of laboratory tests on meta-sandstone samples from a quarry in Nova Scotia, canada. A distinct element code(PFC2D) was used to generate a bonded particle model(BPM) to simulate both the static and dynamic properties of the intact rock. The calibrated BPM was then used to construct large-scale jointed rock mass samples by incorporating discrete joint networks of multiple joint intensities into the intact rock matrix represented by the BPM. Finally, the impact-induced damage inflicted by a rigid projectile particle on the jointed rock mass samples was determined through the use of the numerical model. The simulation results show that joints play an important role in the impactinduced rock mass damage where higher joint intensity results in more damage to the rock mass. This is mainly attributed to variations of stress wave propagation in jointed rock masses as compared to intact rock devoid of joints.

关键词： Jointed rock mass Impact loading Microcracks Rock damage

Progress in twin roll casting of magnesium alloys: A review

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Journal of Magnesium and Alloys 2021年第2期9卷 362-391页

作者： Amjad Javaid Frank Czerwinski CanmetMATERIALS Natural Resources CanadaHamiltonOntarioL8P 0A5Canada

Twin roll casting was commercialized for a strip production from ferrous and non-ferrous alloys in the 1950 s;however,its application to magnesium has proven difficult and still creates major challenges.This report describes global efforts in expanding manufacturing capabilities of magnesium sheet through twin roll casting path,offering many benefits,including a reduction in number of processing steps and energy savings.In addition to hardware design,alloy transformation during processing,product microstructure and properties,examples of successful solutions along with present technology and knowledge limitations are discussed.A particular attention is paid to developments at Canmet MATERIALS,having the only in North America pilot scale twin roll casting facility,devoted to magnesium.Efforts are described that aim at design of new magnesium alloys,which could take advantage of unique processing conditions during twin roll casting and contribute to the overall progress in magnesium sheet manufacturing.

关键词： Twin roll casting Magnesium alloys Solidification Magnesium sheet

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超细晶钒微合金化双相钢性能

钢铁钒钛 2017年第4期38卷 94-104页

作者： C.P.Scott F.Fazeli B.Shalchi I.Pushkareva 杨雄飞 Canmet Materials Natural Resources Canada

研究了钒微合金化对高强双相钢微观组织及性能的影响。与Fe-0.186C-1.5Mn-0.3Si-0.008N参照钢相比,加入0.14%V带来如下效果:(1)在冷轧及退火状态铁素体晶粒高度细化;(2)严重推迟在连续退火过程中铁素体向奥氏体转变的初始动力学;(3)慢... 详细信息

研究了钒微合金化对高强双相钢微观组织及性能的影响。与Fe-0.186C-1.5Mn-0.3Si-0.008N参照钢相比,加入0.14%V带来如下效果:(1)在冷轧及退火状态铁素体晶粒高度细化;(2)严重推迟在连续退火过程中铁素体向奥氏体转变的初始动力学;(3)慢冷条件下铁素体开始转变温度稍微提高,但珠光体和贝氏体转变被抑制,导致淬透性提高;(4)在临界退火温度≤740℃时观察到未溶渗碳体;(5)750℃/180 s退火后铁素体相中发现大量V(C,N)析出(平均直径7.4 nm),而马氏体(奥氏体)中析出物稀少,尺寸更大(平均直径13.4 nm);(6)不含钒参照钢抗拉强度随马氏体体积分数增量为~16 MPa/%,而含钒钢由于晶粒细化和铁素体选择强化,强度随马氏体含量变化增量相当低(~4 MPa/%),在马氏体体积分数>45%变软。

关键词： DP钢 AHSS 超细晶钒微合金化

Microstructure,texture and mechanical behavior characterization of hot forged cast ZK60 magnesium alloy

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Journal of Materials Science & Technology 2017年第9期33卷 907-918页

作者： S.M.H.Karparvarfard S.K.Shaha S.B.Behravesh H.Jahed B.W.Williams Department of Mechanical & Mechatronics Engineering University of Waterloo Canmet MATERIALS Natural Resources Canada

structure with a significant reduction in casting porosity, while the texture changed to sharp basaMeasured mechanical properties of the forged alloy showed that strength did not change, howductility improved by 75%. The analysis of the fracture surface of the forged alloy under tension rea ductile fracture with dimple morphology, while the as-cast alloy displayed a brittle fracture with pores. This demonstrated that the reduction of casting defects and dendritic morphology, as well evolution of recrystallized grains, enhanced ductility, while partial dynamic recrystallization throuforging process resulted in only marginal modification of strength in the forged condition.. 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials SciTechno

关键词： Magnesium Forging Ductility Texture Recrystallization