812 research outputs found
Design of EGR Solenoid Valve Controller using Neural Networks
No full textThis paper describes an initial investigation into the use of neural network learning algorithms to obtain a controller for a non-linear system over a large operating space within the context of automotive applications. In order to perform a comparative study of the various adaptive systems, the problem of controlling the motion of a solenoid-operated EGR (Exhaust Gas Recirculation) valve is considered. This study also compares a neurocontroller with a PID controller for various position step changes in both directions. During the investigation it was found that the performance of the neurocontroller was consistently better, particularly for large demanded step changes, and that the neurocontroller consistently used less control energy. Further work will focus on why these nonlinear learning systems outperform perform PID controllers in this application
Turkey Point Flux Station 1989 Forest (TP2)
No full textThe ON-TP89 site, also known as the CA-TP2 on Global Fluxnet and ON-WPP89 in some of the Fluxnet-Canada Research Network (FCRN)/Canadian Carbon Program (CCP) publications. ON-TP89 is a young planted white pine (Pinus strobusL.) forest of the Turkey Point Flux Station. It was planted in 1989 (ON-TP89) on a former agricultural land. Meteorological and flux data collection was started in summer 1989. The data documented here includes carbon, water and energy fluxes and meteorological and
soil measurements. A unique aspect of Turkey Point Flux Station is its geographic location between the boreal and the broadleaf deciduous forest transition zone. It provides an excellent opportunity to investigate and quantify the strength of the carbon sink or source for planted temperate conifer forests, and its sensitivity to seasonal and annual climate variability. Also white pine is an important species in the North American landscape, because of its ability to adapt to dry enviro
nments. It grows efficiently on nutrient poor, dry, sandy soils. Generally, it is the first woody species to flourish after a disturbance such as fire or clearing and over longer time periods helps more native forest species to establish through succession. White pine trees can live for about 350–400 years and their height may reach up to 45–60 m. These characteristics make white pine a preferred plantation (afforestation) species in eastern North America.
Fluxes, meteorological and soil measurement conducted at this site help us to explore carbon sequestration potential of chronosequence of planted or afforested white pine stands in southern Ontario. The main objectives are (i) to make year-round measurements of energy, water vapour and carbon dioxide (CO2) fluxes and other meteorological variables over mature, middle-aged, young and seedling white pine plantation forests (established in 1939, 1974, 1989 and 2002) (ii) to relate gross ph
otosynthesis and respiration of this stand to environmental factors (iii) determine the effects of seasonal and inter-annual climate variability on net ecosystem productivity, and to better understand the processes of
production, storage and transport of soil CO2 and (iv) use these data to further improve process-based photosynthesis and respiration models.
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Turkey Point Flux Station 2002 Forest (TP1)
No full textThe ON-TP02 site, also known as the CA-TP1 on Global Fluxnet and ON-WPP02 in some of the Fluxnet-Canada Research Network (FCRN)/Canadian Carbon Program (CCP) publications. ON-TP02 is a recently planted white pine (Pinus strobusL.) forest of the Turkey Point Flux Station. It was planted in 2002 (ON-TP02) on a former agricultural land. Meteorological and flux data collection was started in summer 2002. The data set documented here includes carbon, water and energy fluxes and meteorologi
cal and soil measurements. A unique aspect of Turkey Point Flux Station is its geographic location between the boreal and the broadleaf deciduous forest transition zone. It provides an excellent opportunity to investigate and quantify the strength of the carbon sink or source for planted temperate conifer forests, and its sensitivity to seasonal and annual climate variability. Also white pine is an important species in the North American landscape, because of its ability to adapt to dry
environments. It grows efficiently on nutrient poor, dry, sandy soils. Generally, it is the first woody species to flourish after a disturbance such as fire or clearing and over longer time periods helps more native forest species to establish through succession. White pine trees can live for about 350–400 years and their height may reach up to 45–60 m. These characteristics make white pine a preferred plantation (afforestation) species in eastern North America.
Fluxes, meteorological and soil measurement conducted at this site help us to explore carbon sequestration potential of chronosequence of planted or afforested white pine stands in southern Ontario. The main objectives are (i) to make year-round measurements of energy, water vapour and carbon dioxide (CO2) fluxes and other meteorological variables over mature, middle-aged, young and seedling white pine plantation forests (established in 1939, 1974, 1989 and 2002) (ii) to relate gross ph
otosynthesis and respiration of this stand to environmental factors (iii) determine the effects of seasonal and inter-annual climate variability on net ecosystem productivity, and to better understand the processes of production, storage and transport of soil CO2 and (iv) use these data to further improve process-based photosynthesis and respiration models.
More information about the site and associated data can be found in the metadata documentation.</p
Turkey Point Flux Station 1939 Forest (TP4)
No full textThe ON-TP39 site, also known as the CA-TP4 on Global Fluxnet and ON-WPP39 in some of the Fluxnet-Canada Research Network (FCRN)/Canadian Carbon Program (CCP) publications. ON-TP39 is the mature eastern white pine (Pinus strobusL.) forest of the Turkey Point Flux Station. It was planted in 1939 (ON-TP39) on cleared oak-savannah land. Meteorological data collection was started in late autumn 2001 and flux measurements were started in June 2002. The data set documented here includes carb
on, water and energy fluxes and meteorological and soil measurements.
A unique aspect of Turkey Point Flux Station is its geographic location between the boreal and the broadleaf deciduous forest transition zone. It provides an excellent opportunity to investigate and quantify the strength of the carbon sink or source for planted temperate conifer forests, and its sensitivity to seasonal and annual climate variability. Also white pine is an important species in the North American landscape, because of its ability to adapt to dry environments. It grows eff
iciently on nutrient poor, dry, sandy soils. Generally, it is the first woody species to flourish after a disturbance such as fire or clearing and over longer time periods helps more native forest species to establish through succession. White pine trees can live for about 350–400 years and their height may reach up to 45–60 m. These characteristics make white pine a preferred plantation (afforestation) species in eastern North America.
Fluxes, meteorological and soil measurement conducted at this site help us to explore carbon sequestration potential of chronosequence of planted or afforested white pine stands in southern Ontario. The main objectives are (i) to make year-round measurements of energy, water vapour and carbon dioxide (CO2) fluxes and other meteorological variables over mature, middle-aged, young and seedling white pine plantation forests (established in 1939, 1974, 1989 and 2002) (ii) to relate gross ph
otosynthesis and respiration of this stand to environmental factors (iii) determine the effects of seasonal and inter-annual climate variability on net ecosystem produc
tivity, and to better understand the processes of production, storage and transport of soil CO2 and (iv) use these data to further improve process-based photosynthesis and respiration models.
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Different climate conditions drive variations in gross primary productivity and woody biomass accumulation in a temperate and a boreal conifer forest in Canada
No full textUnderstanding the complex relationships between climate, forest carbon (C) uptake and biomass growth has
become a research priority, crucial for assessing the climate change impacts on forest C sequestration. Such
associations are expected to vary across biomes, due to different climate constraints on tree physiology. However,
our understanding of the seasonal dynamics of long-term C sequestration and how climate influences them
in different forest biomes is still limited.
We investigated a boreal Pinus banksiana forest (Old Jack Pine, OJP) and a temperate Pinus strobus plantation
(Turkey Point, TP39) in Canada. We aimed to assess the link between C uptake and above-ground woody biomass
growth, and the effects of climate inter-annual variability on them. We used daily records of climate and gross
primary productivity (GPP, period 1999–2019 at OJP and 2003–2018 at TP39), and investigated xylem biomass
proxies at cell (cell wall area) and tree-ring level (ring wall area) from 1970 to 2019 at OJP, and from 1970 to
2018 at TP39.
In both forests, the direct link between C sink and C source was revealed by the common inter-annual variability
of GPP and xylem biomass. GPP and xylem biomass were mostly influenced by spring and late summer
temperature at OJP. However, at both sites, summer drought negatively influenced GPP, and biomass growth
especially in recent decades. Analysis of dry and cold years evidenced short-term negative effects of low temperature
on GPP and xylem biomass in OJP, and of drought in TP39.
Long-term intra-annual analyses are crucial to assess the variable effects of climate on forest C cycle. Warm
spring and autumn can benefit both GPP and biomass growth, but even in the boreal forest, summer drought has negative impacts. Increasing dry spells, especially in the temperate site, could reduce future forest capacity to uptake C and fix it in wood biomass
The impact of induced drought on transpiration and growth in a temperate pine plantation forest
No full textThe effects of early growing season droughts on water and carbon balances in conifer forests are poorly understood. In this study, the response of canopy transpiration (Ec) and growth rates to reduced precipitation input during the early growing season was evaluated in a 70-year old temperate white pine (Pinus strobus L.) plantation forest, in Southern Ontario, Canada. In order to induce the drought, a 20 x 20?m throughfall exclusion setup was established. Throughfall was excluded from 1 April to 3 July 2009. During this period, 270?mm of rainfall occurred (27% of annual precipitation), of which more than 90% was excluded. Sapflow, stem growth, soil moisture and soil temperature were measured in both drought and reference plots. Prior to the induced drought, both plots showed similar soil water content, transpiration rates and tree diameters. The primary control on forest water loss was vapour pressure deficit, whereas soil moisture had an effect when it reached below 0.068?m3?m-3 during the growing season. The rainfall exclusion did not negatively affect Ec until early June, approximately 54?days after drought initiation. Ec was 27% less in the drought plot compared to the reference plot when evaluated at the end of the growing season in November. Tree growth estimates at the end of the growing season indicated a 17% decrease in growth in the drought plot as compared to the reference plot. Because climate predictions foresee changes in precipitation pattern, drought spells similar to this artificial short-term rainfall manipulation may be more frequent in the future. Hence, although overall precipitation may remain the same, the short-term deficit in water supply may have important implications for forest ecosystems. The findings of this rainfall manipulation will help quantify the impacts of spring and early summer water deficit on forest ecosystems and evaluate their potential responses to future climate regimes. Copyright (C) 2012 John Wiley & Sons, Ltd
Future Smartphone: MIMO Antenna System for 5G Mobile Terminals
No full textIn this article, an inverted L-shaped monopole eight elements Multiple Input Multiple Output (MIMO) antenna system is presented. The multi-antenna system is designed on a low cost 0.8 mm thick FR4 substrate having dimensions of 136 x 68 mm(2) resonating at 3.5GHz with a 6dB measured bandwidth of 450MHz, and with inter element isolation greater than 15 dB and gain of 4 dBi. The proposed design consists of eight inverted L-shaped elements and parasitic L-shaped strips extending from the ground plane. These shorted stripes acted as tuning stubs for the four inverted L-shaped monopole elements on the side of chassis. This is done to achieve the desired frequency range by increasing the electrical length of the antennas. A prototype is fabricated, and the experimental results show good impedance matching with reasonable measured isolation within the desired frequency range. The MIMO performances, such as envelope correlation coefficient (ECC) and mean effective gain (MEG) are also calculated along with the channel capacity of 38.1bps/Hz approximately 2.6 times that of 4 x 4 MIMO system. Due to its simple shape and slim design, it may be a potential chassis for future handsets. Therefore, user hand scenarios, i.e. both single and dual hand are studied. Also, the effects of hand scenarios on various MIMO parameters are discussed along with the SAR. The performance of the proposed system in different scenarios suggests that the proposed structure holds promising future within the next generation radio smart phones
Carbon dynamics and greenhouse gas exchanges in an age-sequence of temperate pine forests
No full text Forest ecosystems play an important role in the global carbon (C) cycle by exchanging large amounts of carbon dioxide (CO₂) with the atmosphere. Their potential to act as significant sink for atmospheric CO₂ has been recognized and is relevant to current efforts in reducing atmospheric CO₂ concentrations. Besides the most important greenhouse gas CO₂, forests also emit and consume methane (CH₄) and nitrous oxide (N₂O) as the two other important atmospheric greenhouse gases (GHGs). To date, few attempts have been made to quantify the net effect of forest GHG exchange on the global warming potential. Furthermore, a better understanding of successional and environmental effects on forest processes is required to improve large scale estimates of forest C and GHG exchange. This thesis examines C dynamics and the exchange of the three major greenhouse gases (CO₂, CH₄, and N₂O) in an age-sequence (7-, 20-, 35-, and 70-years-old as of 2009) of afforested pine forests, in southern Ontario, Canada. The impacts of environmental controls on these GHG exchanges were also evaluated. Forest C exchange was determined for 2003 to 2008 using the eddy-covariance (EC) technique and inventory-based biometric measurements. Soil CH₄ and N₂O measurements were conducted from 2006 to 2007 using the static closed-chamber method. In addition, concentrations and fluxes of dissolved organic carbon (DOC) throughout the vertical profile in forest canopy and soil were determined from 2004 to 2005 using throughfall buckets and lysimeters. During periods without climatic constraints, monthly gross ecosystem productivity (GEP) and ecosystem respiration (RE) corrected for differences in site index increased with stand age, whereas monthly net ecosystem productivity (NEP) peaked at the 35-year-old site. In contrast, during constrained periods (e.g. seasonal drought events), monthly GEP and NEP at the 20-year-old site were higher compared to the 35-year-old site because trees may have benefited from sustained availability of soil water in deeper layers. This study further demonstrates that differences in site quality may affect the interpretation of age-related C flux dynamics in chronosequence and synthesis studies (Chapter 2). The temperature-RE relationship was an important control on daily NEP anomalies under optimum growing conditions, whereas constrains on GEP primarily determined NEP during environmentally constrained periods. Furthermore, effects from single environmental variable constrains on NEP anomalies were enhanced as well as outbalanced under multiple environmental variable constrains. The results further indicate that future changes in temperature and precipitation patterns towards drier and warmer conditions as well as greater cloud cover may result in reduced C sequestration potentials in these temperate pine forests (Chapter 3). Early summer drought and heat events in 2005 caused NEP to decrease by approximately 100 g C m⁻² y⁻¹ at each site compared to the other years. This decrease was primarily driven by a decrease in photosynthesis, while the effect of these events on ecosystem respiration was small. Overall, for the years 2003-2007, annual NEP was 219, 155, 36, 148, and 120 g C m⁻² y⁻¹ at the 68-year-old site, 666, 318, 346, 511 and 366 g C m⁻² y⁻¹ at the 33-year-old site, 768, 885, 684, 708 and 826 g C m⁻² y⁻¹ at the 18-year-old site, and-18, 145, 125, 34 and 164 g C m⁻² y⁻¹ at the 5-year-old seedling site, respectively (negative numbers indicating net C source (Chapter 4). Four-year mean values of biometric NEP_(B) and EC-based NEP_(EC) were similar at the 7-year-old seedling (77 and 66 g C m⁻² y⁻¹) and the 70-year-old mature site (135 and 124 g C m⁻² y⁻¹), but differed considerably at the 20-year-old (439 and 736 g C m⁻² y⁻¹) and the 35-year-old sites (170 and 392 g C m⁻² y⁻¹). Integrating NEP across the age-sequence resulted in a total net C sequestration of 137 and 229 t C ha⁻¹ over the initial 70 years as estimated by the biometric and EC method, respectively. The total ecosystem C pool at the 70-year-old site suggested an accumulation of 160 t C ha⁻¹. These three estimates resulted in a mean C sequestration of 175 ± 48 t C ha⁻¹ (Chapter 5). For both CH₄ and N₂O, we observed uptake and emission ranging from -160 to 245 μg CH₄ m⁻² hour⁻¹ and -52 to 21 μg N₂O m⁻² hour⁻¹, respectively (negative values indicate net uptake). Mean N₂O fluxes from mid-April to mid-December across the 7-, 20-, 35-, 70-years old stands were -3.7, 1.5, -2.2, and-7.6 μg N₂O m⁻² hour⁻¹, without age-related pattern, whereas the uptake rates of CH₄ increased with stand age from 6.4 to -7.9, -10.8, and-23.3 μg CH₄ m⁻² hour⁻¹, respectively. For the same period, the combined contribution of CH₄ and N₂O exchanges to the global warming potential (GWP) calculated from net ecosystem exchange of CO₂ and aggregated forest floor exchanges of CH₄ and N₂O was on average DOC concentration in forest floor leachates was positively correlated to stand age, aboveground biomass and forest floor carbon pools. From the period of Mid-April to December, DOC fluxes via precipitation, throughfall, and leaching through forest floor and Ah-horizon were in the range of ~1 to 2, 2 to 4, 0.5 to 3.5, and 0.1 to 2 g DOC m⁻², respectively. DOC export from the forest ecosystem during that period through infiltration and groundwater discharge decreased with increasing stand age from ~7 to 4, 3, and 2 g DOC m⁻² (Chapter 7). This thesis improved our understanding of C and GHG exchange dynamics and their environmental, physical, and physiological controls in forest ecosystems. This study will also contribute to efforts being made to better predict future forest C and GHG dynamics and their feedbacks on climate under changing environmental conditions. ThesisDoctor of Philosophy (PhD
Analysis of nitrogen controls on carbon and water exchanges in a conifer forest using CLASS-CTEMᴺ⁺ model
No full textNitrogen (N) controls on carbon and water exchanges were analyzed in a 70-year old eastern temperate conifer forest in Ontario, Canada from 2003 to 2007 using a newly developed nitrogen (N) cycle coupled model -- CLASS-CTEMᴺ⁺. This process-based model incorporates sunlit and shaded big-leaves for C3 and C4 photosynthesis and semi-mechanistic canopy conductance formulation for dynamic plant-functional-types. Recently, key soil and plant N cycling algorithms have also been included (e.g., biological fixation, atmospheric N deposition, fertilization, mineralization, nitrification, denitrification, leaching, soil nitrous dioxide (N₂0) emissions, root N uptake, plant N allocation and N controls on plant photosynthesis capacity). The simulated values of soil-plant N contents and processes rates including N₂0 fluxes were generally in agreement with observations. Comparison of default non-N and C&N-coupled model simulations clearly revealed N controls on photosynthetic uptake and water loss. Predictions of daily gross ecosystem productivity (GEP), ecosystem respiration (Re), net ecosystem productivity (NEP) and evapotranspiration (ET) showed better agreement with eddy covariance (EC) flux measurements when using the N-coupled model (RMSE of 1.97, 0.73, 1.44, 0.92; and MAE of 1.48, 0.55, 1.01, 0.60 for GEP, Re, NEP, and ET, respectively; n=1825) as compared to the non-N model simulations (RMSE of2.95, 1.35, 1.93, 1.03; MAE of2.38, 1.15, 1.55,0.71 for GEP, Re, NEP, and ET, respectively; n=1825) over 5 years (2003-2007). Annual values of N-coupled model simulated NEP were 134, 195, 183, 225 and 255 g C m⁻² yr⁻¹ for 2003-2007, as compared to non-N model simulated annual NEP values, which were 535, 562, 507, 540, and 535 g C m⁻² yr⁻¹ for respective years. These values were compared to measured NEP values of 220±67, 126±67, 33±67, 142±67 and 102±67 g C m⁻² yr⁻¹ for the years 2003-2007, respectively. The difference between N-coupled model simulated and EC measured annual variations of carbon exchanges was largely due to specific extreme weather events (e.g. drought, spring warming) during certain years. Overall, the impacts of N limitations on carbon fluxes were more pronounced during early spring, late autumn and winter seasons. This newly developed model will help to evaluate the response of terrestrial vegetation ecosystems to N variations under different scenarios for future climate change.Master of Science (MS
What is a pilot or feasibility study? A review of current practice and editorial policy
No full textBackground: In 2004, a review of pilot studies published in seven major medical journals during 2000-01 recommended that the statistical analysis of such studies should be either mainly descriptive or focus on sample size estimation, while results from hypothesis testing must be interpreted with caution. We revisited these journals to see whether the subsequent recommendations have changed the practice of reporting pilot studies. We also conducted a survey to identify the methodological components in registered research studies which are described as 'pilot' or 'feasibility' studies. We extended this survey to grant-awarding bodies and editors of medical journals to discover their policies regarding the function and reporting of pilot studies.
Methods: Papers from 2007-08 in seven medical journals were screened to retrieve published pilot studies. Reports of registered and completed studies on the UK Clinical Research Network (UKCRN) Portfolio database were retrieved and scrutinized. Guidance on the conduct and reporting of pilot studies was retrieved from the websites of three grant giving bodies and seven journal editors were canvassed.
Results: 54 pilot or feasibility studies published in 2007-8 were found, of which 26 (48%) were pilot studies of interventions and the remainder feasibility studies. The majority incorporated hypothesis-testing (81%), a control arm (69%) and a randomization procedure (62%). Most (81%) pointed towards the need for further research. Only 8 out of 90 pilot studies identified by the earlier review led to subsequent main studies. Twelve studies which were interventional pilot/feasibility studies and which included testing of some component of the research process were identified through the UKCRN Portfolio database. There was no clear distinction in use of the terms 'pilot' and 'feasibility'. Five journal editors replied to our entreaty. In general they were loathe to publish studies described as 'pilot'.
Conclusion: Pilot studies are still poorly reported, with inappropriate emphasis on hypothesis-testing. Authors should be aware of the different requirements of pilot studies, feasibility studies and main studies and report them appropriately. Authors should be explicit as to the purpose of a pilot study. The definitions of feasibility and pilot studies vary and we make proposals here to clarify terminology
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