We report the confirmation of a sub-Saturn-size exoplanet,TOI-1194 b,with a mass of about 0.456+0.055-0.051M_(J),and a very low mass companion star with a mass of about 96.5±1.5 MJ,TOI-1251 B.Exoplanet candidates...We report the confirmation of a sub-Saturn-size exoplanet,TOI-1194 b,with a mass of about 0.456+0.055-0.051M_(J),and a very low mass companion star with a mass of about 96.5±1.5 MJ,TOI-1251 B.Exoplanet candidates provided by the Transiting Exoplanet Survey Satellite(TESS)are suitable for further follow-up observations by ground-based telescopes with small and medium apertures.The analysis is performed based on data from several telescopes worldwide,including telescopes in the Sino-German multiband photometric campaign,which aimed at confirming TESS Objects of Interest(TOIs)using ground-based small-aperture and medium-aperture telescopes,especially for long-period targets.TOI-1194 b is confirmed based on the consistent periodic transit depths from the multiband photometric data.We measure an orbital period of 2.310644±0.000001 days,the radius is 0.767+0.045-0.041RJ and the amplitude of the RV curve is 69.4_(-7.3)^(+7.9)m s^(-1).TOI-1251 B is confirmed based on the multiband photometric and high-resolution spectroscopic data,whose orbital period is 5.963054+0.000002-0.000001days,radius is 0.947+0.035-0.033 R_(J) and amplitude of the RV curve is 9849_(-40)^(+42)ms^(-1).展开更多
In the summer of 2015,hundreds of forest fires burned across the state of Alaska.Several uncontrolled wildfires near the town of Tanana on the Yukon River were responsible for the largest portion of the area burned st...In the summer of 2015,hundreds of forest fires burned across the state of Alaska.Several uncontrolled wildfires near the town of Tanana on the Yukon River were responsible for the largest portion of the area burned statewide.In July 2017,field measurements were carried out in both unburned and burned forested areas nearly adjacent to one another,all within 15 miles of the village of Tanana.These surveys were used to first visually verify locations of different burn severity classes,(low,moderate,or high),estimated in 2016 from Landsat images(collected before and after the 2015 Tanana-area wildfires).Surface and soil profile measurements to 30-cm depth at these same locations were collected for evidence of moss layer and forest biomass burning.Soil temperature and moisture content were measured to 30-cm depth,and depth to permafrost was estimated by excavation wherever necessary.Digital thermal infra-red images of the soil profiles were taken at each site location,and root-zone organic layer samples were extracted for further chemical analysis.Results supported the hypothesis that the loss of surface organic layers is a major factor determining post-fire soil water and temperature changes and the depth of permafrost thawing.In the most severely burned forest sites,complete consumption of the living moss organic layer was strongly associated with both warming at the surface layer and increases in soil water content,relative to unburned forest sites.Soil temperatures at both 10-cm and 30-cm depths at burned forest sites were higher by 8-10C compared to unburned sites.Below 15 cm,temperatures of unburned sites dropped gradually to frozen levels by 30 cm,while soil temperatures at burned sites remained above 5C to 30-cm depth.The water content measured at 3 cm at burned sites was commonly in excess of 30%by volume,compared to unburned sites.The strong correlation between burn index values and depth to permafrost measured across all sites sampled in July 2017 showed that the new ice-free profile in severely burned forest areas was commonly 50-cm deeper than in unburned soils.展开更多
OMEGA is a system for cultivating microalgae using wastewater contained in floating photobioreactors (PBRs) deployed in marine environments and thereby eliminating competition with agriculture for water, fertilizer, a...OMEGA is a system for cultivating microalgae using wastewater contained in floating photobioreactors (PBRs) deployed in marine environments and thereby eliminating competition with agriculture for water, fertilizer, and land. The offshore placement in protected bays near coastal cities co-locates OMEGA with wastewater outfalls and sources of CO2-rich flue gas on shore. To evaluate the feasibility of OMEGA, microalgae were grown on secondary-treated wastewater supplemented with simulated flue gas (8.5% CO2 V/V) in a 110-liter prototype system tested using a seawater tank. The flow-through system consisted of tubular PBRs made of transparent linear low-density polyethylene, a gas exchange and harvesting column (GEHC), two pumps, and an instrumentation and control (I&C) system. The PBRs contained regularly spaced swirl vanes to create helical flow and mixing for the circulating culture. About 5% of the culture volume was continuously diverted through the GEHC to manage dissolved oxygen concentrations, provide supplemental CO2, harvest microalgae from a settling chamber, and add fresh wastewater to replenish nutrients. The I&C system controlled CO2 injection and recorded dissolved oxygen levels, totalized CO2 flow, temperature, circulation rates, photosynthetic active radiation (PAR), and the photosynthetic efficiency as determined by fast repetition rate fluorometry. In two experimental trials, totaling 23 days in April and May 2012, microalgae productivity averaged 14.1 ± 1.3 grams of dry biomass per square meter of PBR surface area per day (n = 16), supplemental CO2 was converted to biomass with >50% efficiency, and >90% of the ammonia-nitrogen was recovered from secondary effluent. If OMEGA can be optimized for energy efficiency and scaled up economically, it has the potential to contribute significantly to biofuels production and wastewater treatment.展开更多
Near-nadir observations by the Multispectral Instrument (MSI) onboard the Sentinel-2 and the Operational Land Imager (OLI) onboard Landsat 8 were collected during two Simultaneous Nadir Overpasses (SNO). Multispectral...Near-nadir observations by the Multispectral Instrument (MSI) onboard the Sentinel-2 and the Operational Land Imager (OLI) onboard Landsat 8 were collected during two Simultaneous Nadir Overpasses (SNO). Multispectral images with 10, 20, and 30 m resolution from a spatially uniform area in the Saharan desert were acquired for direct comparison of MSI and OLI Top- Of-Atmosphere (TOA) reflectances. This paper presents an initial radiometric cross-calibration of the 8 corresponding spectral bands of the Sentinel-2 MSI and Landsat 8 OLI sensors. With the well-calibrated Landsat 8 OLI as a reference, the comparison indicates that 6 MSI bands are consistent with OLI within 3% in terms of spectral band adjustment factors Bi . The Near-Infra-Red (NIR) and cirrus bands are exceptions. They yield radiometric differences on the order of 8% and 15% respectively. Cross-calibration results show that the radiometric difference of the 7 corresponding bands are consistent to OLI within 1% or better, except on cirrus band. A pixel-by-pixel match between the MSI and OLI observations for different land covers showed that. This initial study suggests that the red-edge band B8A of MSI can be used to replace the NIR band B08 when conducting vegetation monitoring.展开更多
Carbon nanotubes CNTs)have been receiving enormous attention in the last decade due to their extraordinary mechanical properties and unique elec- tronic properties.This combination has produced an unprecedented range ...Carbon nanotubes CNTs)have been receiving enormous attention in the last decade due to their extraordinary mechanical properties and unique elec- tronic properties.This combination has produced an unprecedented range of applications for CNTs:elec- tronic,logic and memory chips,chemical and biosen- sots,composites,lithium batteries,gas storage,filters and membranes,etc.This presentation will focus on carbon nanotube based sensors and discuss fabrication, testing and performance.展开更多
In this study, we present results from the CASA (Carnegie-Ames-Stanford Approach) model to estimate net primary production (NPP) in grasslands under different management (ranching versus unmanaged) on the Central Coas...In this study, we present results from the CASA (Carnegie-Ames-Stanford Approach) model to estimate net primary production (NPP) in grasslands under different management (ranching versus unmanaged) on the Central Coast of California. The latest model version called CASA Express has been designed to estimate monthly patterns in carbon fixation and plant biomass production using moderate spatial resolution (30 m to 250 m) satellite image data of surface vegetation characteristics. Landsat imagery with 30 m resolution was adjusted by contemporaneous Moderate Resolution Imaging Spectroradiometer (MODIS) data to calibrate the model based on previous CASA research. Results showed annual NPP predictions of between 300 - 450 grams C per square meter for coastal rangeland sites. Irrigation increased the predicted NPP carbon flux of grazed lands by 59 grams C per square meter annually compared to unmanaged grasslands. Low intensity grazing activity appeared to promote higher grass regrowth until June, compared to the ungrazed grassland sites. These modeling methods were shown to be successful in capturing the differing seasonal growing cycles of rangeland forage production across the area of individual ranch properties.展开更多
The KCI：Eu2＋ system response to UV-C was investigated by analyzing the optically stimulated luminescence （OSL） and ther- mo-luminescence （TL） signal produced by ultraviolet light exposure at room temperature. It...The KCI：Eu2＋ system response to UV-C was investigated by analyzing the optically stimulated luminescence （OSL） and ther- mo-luminescence （TL） signal produced by ultraviolet light exposure at room temperature. It was found that after UV-C irra.diation, OSL was produced on a wide band of visible wavelengths with decay time that varied by several orders of magnitude depending on the Eu2＋ aggregation state. In spite of the low intensity of solar UV-C reaching the Earth＇s surface in Madrid （40° N, 700 m a.s.1.）, it was possible to measure the UV-C radiation dose at 6：48 solar time by using the TL response of the KCI：Eu2＋ system and differentiate it from the ambient beta radiation dose.展开更多
A simulation model to estimate net primary productivity (NPP) has been combined with in situ measurements of soil carbon dioxide (CO2) emissions and leaf litter pools in three coast redwood forest stands on the centra...A simulation model to estimate net primary productivity (NPP) has been combined with in situ measurements of soil carbon dioxide (CO2) emissions and leaf litter pools in three coast redwood forest stands on the central California coast. Monthly NPP was predicted from the CASA model using 250-meter resolution vegetation index (VI) inputs. Annual NPP was predicted to vary from 380 g·C·m-2·yr-1 to 648 g·C·m-2·yr-1 at central coast redwood sites over the years 2007 to 2010. Measured soil respiration rates at between 0.5 to 2.2 g·C·m-2·d-1 were slightly below the range of measurements previously reported for a second-growth mixed (redwood and Douglas-fir) conifer forests. Although warm monthly temperatures at the southern-most redwood forest sites evidently results in elevated stress levels to sustained redwood growth into the dry summer months of June and July, these redwood stands appear to sequester CO2 from that atmosphere into forest biomass for a net positive ecosystem carbon balance each year.展开更多
This study evaluates the long-term radiometric performance of the USGS new released Landsat Collection 1 archive, including the absolute calibration of each Landsat sensor as well as the relative cross-calibration amo...This study evaluates the long-term radiometric performance of the USGS new released Landsat Collection 1 archive, including the absolute calibration of each Landsat sensor as well as the relative cross-calibration among the four most popular Landsat sensors. A total of 920 Landsat Collection 1 scenes were evaluated against the corresponding Pre-Collection images over a Pseudo-Invariant Site, Railroad Valley Playa Nevada, United States (RVPN). The radiometric performance of the six Landsat solar reflective bands, in terms of both Digital Numbers (DNs) and at-sensor Top of Atmosphere (TOA) reflectance, on the sensor cross-calibration was examined. Results show that absolute radiometric calibration at DNs level was applied to the Landsat-4 and -5 TM (L4 TM and L5 TM) by –1.119% to 0.126%. For L4 TM and L5 TM, the cross-calibration decreased the radiometric measurement level by rescaling at-sensor radiance to DN values. The radiometric changes, –0.77% for L4 TM, 0.95% for L5 TM, –0.26% for L7 ETM+, and –0.01% for L8 OLI, were detected during the cross-calibration stage of converting DNs into TOA reflectance. This study has also indicated that the long-term radiometric performance for the Landsat Collection 1 archive is promising. Supports of these conclusions were demonstrated through the time-series analysis based on the Landsat Collection 1 image stack. Nevertheless, the radiometric changes across the four Landsat sensors raised concerns of the previous Landsat Pre-Collection based results. We suggest that Landsat users should pay attention to differences in results from Pre-Collection and Collection 1 time-series data sets.展开更多
The goal of this study was to determine whether climate has affected vegetation regrowth over the past decade (2000 to 2010) in post-fire forest ecosystems of the United States and Canada. Our methodology detected tre...The goal of this study was to determine whether climate has affected vegetation regrowth over the past decade (2000 to 2010) in post-fire forest ecosystems of the United States and Canada. Our methodology detected trends in the monthly MODerate resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) timeseries within forest areas that burned between 1984 and 1999. The trends in summed growing season EVI (composited to 8 km spatial resolution) within all burned area perimeters showed that nearly 1.6% post-fire forest area declined in vegetation greenness cover significantly (p < 0.05) over the past decade. Nearly 62% of all post-fire forest area showed a non significant EVI regrowth trend from 2000 to 2010. Regression results detected numerous significantly negative trend pixels in post-fire areas from 1994-1999 to indicate that forest regrowth has not yet occurred to any measurable level in many recent wildfire areas across the continent. We found several noteworthy relationships between annual temperature and precipitation patterns and negative post-fire forest EVI trends across North America. Change patterns in the climate moisture index (CMI), growing degree days (GDD), and the standardized precipitation index (SPI) were associated with post-fire forest EVI trends. We conclude that temperature warming-induced change and variability of precipitation at local and regional scales may have altered the trends of large post-fire forest regrowth and could be impacting the resilience of post-fire forest ecosystems in North America.展开更多
The Santa Cruz Mountain range in northern California is a coastal landscape with a history of extensive forest logging and frequent large wildfires that have recently destroyed numerous residential structures at the w...The Santa Cruz Mountain range in northern California is a coastal landscape with a history of extensive forest logging and frequent large wildfires that have recently destroyed numerous residential structures at the wildland interface. Results from Landsat satellite image time-series analysis since 1984 of the study area within the Los Gatos Creek and Corralitos Creek watersheds showed that none of the severe drought periods since the 1980s have notably inhibited rapid tree and shrub regrowth rates on steep hill slopes burned recently by the 1985 Lexington Fire and the 2008 Summit Fire. In high burn severity areas of both fires, post-fire vegetation types showed a marked increase in shrub cover, mainly at the expense of evergreen tree cover. Most of these low (<3 m), dense stands of evergreen woody species have regenerated in as little as five years from bare charred ground. A combination of Landsat and Laser Altimeter (GLAS) satellite sensor data revealed that exposed south-facing slopes are presently supporting 200 to 240 Mg·ha<sup>-1</sup> of standing woody biomass on the burned areas. This study is the first of its kind to utilize a full 30-year record of Landsat vegetation index data to monitor tree and shrub regrowth after stand-replacing wildfires in California.展开更多
Fog deposition is a notable component of the water budget of herbaceous-shrub ecosystems on the central and southern coastal regions of California. This paper presents an analysis of fog water deposition rates and met...Fog deposition is a notable component of the water budget of herbaceous-shrub ecosystems on the central and southern coastal regions of California. This paper presents an analysis of fog water deposition rates and meteorological controls in Big Sur, California. Mesh-screen fog collectors were installed the Brazil Ranch weather station sites to measure fog water during the summer seasons of 2010 and 2011. Fog deposition occurred during 73% of days recorded in 2010 and 87% of days recorded in 2011. The daily average deposition rate was 2.29 L/m2 in 2010 and 3.86 L/m2 in 2011. The meteorological variables which had the greatest influence on prediction of fog deposition were wind speed, wind direction, and the dew-point depression (difference between air temperature and dew point). Based on these results, we hypothesize that high rates of summer fog deposition help sustain the productivity of California coastal vegetation through periods of low rainfall.展开更多
Aeroelastic study of flight vehicles has been a subject of great interest and research in the last several years. Aileron reversal and flutter related problems are due in part to the elasticity of a typical airplane. ...Aeroelastic study of flight vehicles has been a subject of great interest and research in the last several years. Aileron reversal and flutter related problems are due in part to the elasticity of a typical airplane. Structural dynamics of an aircraft wing due to its aeroelastic nature are characterized by partial differential equations. Controller design for these systems is very complex as compared to lumped parameter systems defined by ordinary differential equations. In this paper, a stabilizing statefeedback controller design approach is presented for the heave dynamics of a wing-fuselage model. In this study, a continuous actuator in the spatial domain is assumed. A control methodology is developed by combining the technique of “proper orthogonal decomposition” and approximate dynamic programming. The proper orthogonal decomposition technique is used to obtain a low-order nonlinear lumped parameter model of the infinite dimensional system. Then a near optimal controller is designed using the single-network-adaptive-critic technique. Furthermore,to add robustness to the nominal single-network-adaptive-critic controller against matched uncertainties, an identifier based adaptive controller is proposed. Simulation results demonstrate the effectiveness of the single-network-adaptive-critic controller augmented with adaptive controller for infinite dimensional systems.展开更多
This paper presents a new model-reference adaptive control method based on a bi-objective optimal control formulation for systems with input uncertainty. A parallel predictor model is constructed to relate the predict...This paper presents a new model-reference adaptive control method based on a bi-objective optimal control formulation for systems with input uncertainty. A parallel predictor model is constructed to relate the predictor error to the estimation error of the control effectiveness matrix. In this work, we develop an optimal control modification adaptive control approach that seeks to minimize a bi-objective linear quadratic cost function of both the tracking error norm and the predictor error norm simultaneously. The resulting adaptive laws for the parametric uncertainty and control effectiveness uncertainty are dependent on both the tracking error and the predictor error, while the adaptive laws for the feedback gain and command feedforward gain are only dependent on the tracking error. The optimal control modification term provides robustness to the adaptive laws naturally from the optimal control framework. Simulations demonstrate the effectiveness of the proposed adaptive control approach.展开更多
Changes in Earth＇s temperature have significant impacts on the global carbon cycle that vary at different time scales, yet to quantify such impacts with a simple scheme is traditionally deemed difficult. Here, we sho...Changes in Earth＇s temperature have significant impacts on the global carbon cycle that vary at different time scales, yet to quantify such impacts with a simple scheme is traditionally deemed difficult. Here, we show that, by incorporating a tem- perature sensitivity parameter （1.64 ppm yr-1 ℃-1） into a simple linear carbon-cycle model, we can accurately characterize the dynamic responses of atmospheric carbon dioxide （CO2） concentration to anthropogenic carbon emissions and global temperature changes between 1850 and 2010 （r2 〉 0.96 and the root-mean-square error 〈 1 ppm for the period from 1960 onward）. Analytical analysis also indicates that the multiplication of the parameter with the response time of the atmospheric carbon reservoir （-12 year） approximates the long-term temperature sensitivity of global atmospheric CO2 concentration （-15 ppm ℃ 1）, generally consistent with previous estimates based on reconstructed CO2 and climate records over the Little Ice Age. Our results suggest that recent increases in global surface temperatures, which accelerate the release of carbon from the surface reservoirs into the atmosphere, have partially offset surface carbon uptakes enhanced by the elevated atmo- spheric CO2 concentration and slowed the net rate of atmospheric CO2 sequestration by global land and oceans by -30% since the 1960s. The linear modeling framework outlined in this paper thus provides a useful tool to diagnose the observed atmospheric CO2 dynamics and monitor their future changes.展开更多
Biopolymer-bound Soil Composites(BSC),are a novel bio-based construction material class,produced through the mixture and desiccation of biopolymers with inorganic aggregates with applications in soil stabilization,bri...Biopolymer-bound Soil Composites(BSC),are a novel bio-based construction material class,produced through the mixture and desiccation of biopolymers with inorganic aggregates with applications in soil stabilization,brick creation and in situ construction on Earth and space.This paper introduces a mixture design methodology to produce maximum strength for a given soil-biopolymer combination.Twenty protein and sand mix designs were investigated,with varying amounts of biopolymer solution and compaction regimes during manufacture.The ultimate compressive strength,density,and shrinkage of BSC samples are reported.It is observed that the compressive strength of BSC materials increases proportional to tighter particle packing(soil dry bulk density)and binder content.A theory to explain this peak compressive strength phenomenon is presented.展开更多
This paper is focused on adaptively controlling a linear infinite-dimensional system to track a finite-dimensional reference model.Given a linear continuous-time infinite-dimensional plant on a Hilbert space with dist...This paper is focused on adaptively controlling a linear infinite-dimensional system to track a finite-dimensional reference model.Given a linear continuous-time infinite-dimensional plant on a Hilbert space with disturbances of known waveform but unknown amplitude and phase,we show that there exists a stabilizing direct model reference adaptive control law with the properties of certain disturbance rejection and robustness.The plant is described by a closed,densely defined linear operator that generates a continuous semigroup of bounded operators on the Hilbert space of states.The central result will show that all errors will converge to a prescribed neighborhood of zero in an infinitedimensional Hilbert space.The result will not require the use of the standard Barbalat’s lemma which requires certain signals to be uniformly continuous.This result is used to determine conditions under which a linear infinite-dimensional system can be directly adaptively controlled to follow a reference model.In particular,we examine conditions for a set of ideal trajectories to exist for the tracking problem.Our results are applied to adaptive control of general linear diffusion systems described by self-adjoint operators with compact resolvent.展开更多
基金supported by National Natural Science Foundation of China(NSFC,Grant Nos.U1831209 and U2031144)the research fund of Ankara University(BAP)through the project 18A0759001。
文摘We report the confirmation of a sub-Saturn-size exoplanet,TOI-1194 b,with a mass of about 0.456+0.055-0.051M_(J),and a very low mass companion star with a mass of about 96.5±1.5 MJ,TOI-1251 B.Exoplanet candidates provided by the Transiting Exoplanet Survey Satellite(TESS)are suitable for further follow-up observations by ground-based telescopes with small and medium apertures.The analysis is performed based on data from several telescopes worldwide,including telescopes in the Sino-German multiband photometric campaign,which aimed at confirming TESS Objects of Interest(TOIs)using ground-based small-aperture and medium-aperture telescopes,especially for long-period targets.TOI-1194 b is confirmed based on the consistent periodic transit depths from the multiband photometric data.We measure an orbital period of 2.310644±0.000001 days,the radius is 0.767+0.045-0.041RJ and the amplitude of the RV curve is 69.4_(-7.3)^(+7.9)m s^(-1).TOI-1251 B is confirmed based on the multiband photometric and high-resolution spectroscopic data,whose orbital period is 5.963054+0.000002-0.000001days,radius is 0.947+0.035-0.033 R_(J) and amplitude of the RV curve is 9849_(-40)^(+42)ms^(-1).
文摘In the summer of 2015,hundreds of forest fires burned across the state of Alaska.Several uncontrolled wildfires near the town of Tanana on the Yukon River were responsible for the largest portion of the area burned statewide.In July 2017,field measurements were carried out in both unburned and burned forested areas nearly adjacent to one another,all within 15 miles of the village of Tanana.These surveys were used to first visually verify locations of different burn severity classes,(low,moderate,or high),estimated in 2016 from Landsat images(collected before and after the 2015 Tanana-area wildfires).Surface and soil profile measurements to 30-cm depth at these same locations were collected for evidence of moss layer and forest biomass burning.Soil temperature and moisture content were measured to 30-cm depth,and depth to permafrost was estimated by excavation wherever necessary.Digital thermal infra-red images of the soil profiles were taken at each site location,and root-zone organic layer samples were extracted for further chemical analysis.Results supported the hypothesis that the loss of surface organic layers is a major factor determining post-fire soil water and temperature changes and the depth of permafrost thawing.In the most severely burned forest sites,complete consumption of the living moss organic layer was strongly associated with both warming at the surface layer and increases in soil water content,relative to unburned forest sites.Soil temperatures at both 10-cm and 30-cm depths at burned forest sites were higher by 8-10C compared to unburned sites.Below 15 cm,temperatures of unburned sites dropped gradually to frozen levels by 30 cm,while soil temperatures at burned sites remained above 5C to 30-cm depth.The water content measured at 3 cm at burned sites was commonly in excess of 30%by volume,compared to unburned sites.The strong correlation between burn index values and depth to permafrost measured across all sites sampled in July 2017 showed that the new ice-free profile in severely burned forest areas was commonly 50-cm deeper than in unburned soils.
文摘OMEGA is a system for cultivating microalgae using wastewater contained in floating photobioreactors (PBRs) deployed in marine environments and thereby eliminating competition with agriculture for water, fertilizer, and land. The offshore placement in protected bays near coastal cities co-locates OMEGA with wastewater outfalls and sources of CO2-rich flue gas on shore. To evaluate the feasibility of OMEGA, microalgae were grown on secondary-treated wastewater supplemented with simulated flue gas (8.5% CO2 V/V) in a 110-liter prototype system tested using a seawater tank. The flow-through system consisted of tubular PBRs made of transparent linear low-density polyethylene, a gas exchange and harvesting column (GEHC), two pumps, and an instrumentation and control (I&C) system. The PBRs contained regularly spaced swirl vanes to create helical flow and mixing for the circulating culture. About 5% of the culture volume was continuously diverted through the GEHC to manage dissolved oxygen concentrations, provide supplemental CO2, harvest microalgae from a settling chamber, and add fresh wastewater to replenish nutrients. The I&C system controlled CO2 injection and recorded dissolved oxygen levels, totalized CO2 flow, temperature, circulation rates, photosynthetic active radiation (PAR), and the photosynthetic efficiency as determined by fast repetition rate fluorometry. In two experimental trials, totaling 23 days in April and May 2012, microalgae productivity averaged 14.1 ± 1.3 grams of dry biomass per square meter of PBR surface area per day (n = 16), supplemental CO2 was converted to biomass with >50% efficiency, and >90% of the ammonia-nitrogen was recovered from secondary effluent. If OMEGA can be optimized for energy efficiency and scaled up economically, it has the potential to contribute significantly to biofuels production and wastewater treatment.
文摘Near-nadir observations by the Multispectral Instrument (MSI) onboard the Sentinel-2 and the Operational Land Imager (OLI) onboard Landsat 8 were collected during two Simultaneous Nadir Overpasses (SNO). Multispectral images with 10, 20, and 30 m resolution from a spatially uniform area in the Saharan desert were acquired for direct comparison of MSI and OLI Top- Of-Atmosphere (TOA) reflectances. This paper presents an initial radiometric cross-calibration of the 8 corresponding spectral bands of the Sentinel-2 MSI and Landsat 8 OLI sensors. With the well-calibrated Landsat 8 OLI as a reference, the comparison indicates that 6 MSI bands are consistent with OLI within 3% in terms of spectral band adjustment factors Bi . The Near-Infra-Red (NIR) and cirrus bands are exceptions. They yield radiometric differences on the order of 8% and 15% respectively. Cross-calibration results show that the radiometric difference of the 7 corresponding bands are consistent to OLI within 1% or better, except on cirrus band. A pixel-by-pixel match between the MSI and OLI observations for different land covers showed that. This initial study suggests that the red-edge band B8A of MSI can be used to replace the NIR band B08 when conducting vegetation monitoring.
文摘Carbon nanotubes CNTs)have been receiving enormous attention in the last decade due to their extraordinary mechanical properties and unique elec- tronic properties.This combination has produced an unprecedented range of applications for CNTs:elec- tronic,logic and memory chips,chemical and biosen- sots,composites,lithium batteries,gas storage,filters and membranes,etc.This presentation will focus on carbon nanotube based sensors and discuss fabrication, testing and performance.
文摘In this study, we present results from the CASA (Carnegie-Ames-Stanford Approach) model to estimate net primary production (NPP) in grasslands under different management (ranching versus unmanaged) on the Central Coast of California. The latest model version called CASA Express has been designed to estimate monthly patterns in carbon fixation and plant biomass production using moderate spatial resolution (30 m to 250 m) satellite image data of surface vegetation characteristics. Landsat imagery with 30 m resolution was adjusted by contemporaneous Moderate Resolution Imaging Spectroradiometer (MODIS) data to calibrate the model based on previous CASA research. Results showed annual NPP predictions of between 300 - 450 grams C per square meter for coastal rangeland sites. Irrigation increased the predicted NPP carbon flux of grazed lands by 59 grams C per square meter annually compared to unmanaged grasslands. Low intensity grazing activity appeared to promote higher grass regrowth until June, compared to the ungrazed grassland sites. These modeling methods were shown to be successful in capturing the differing seasonal growing cycles of rangeland forage production across the area of individual ranch properties.
基金The support of the DOE/SciDAC SAP grant DE-AI02-06ER25796 is acknowledgedFinancial support from the NASA Aerosciences/RCA program for the second author is gratefully acknowledgedWork by the fifth author was performed under the auspices of the U.S.Department of Energy at Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344
文摘The KCI：Eu2＋ system response to UV-C was investigated by analyzing the optically stimulated luminescence （OSL） and ther- mo-luminescence （TL） signal produced by ultraviolet light exposure at room temperature. It was found that after UV-C irra.diation, OSL was produced on a wide band of visible wavelengths with decay time that varied by several orders of magnitude depending on the Eu2＋ aggregation state. In spite of the low intensity of solar UV-C reaching the Earth＇s surface in Madrid （40° N, 700 m a.s.1.）, it was possible to measure the UV-C radiation dose at 6：48 solar time by using the TL response of the KCI：Eu2＋ system and differentiate it from the ambient beta radiation dose.
文摘A simulation model to estimate net primary productivity (NPP) has been combined with in situ measurements of soil carbon dioxide (CO2) emissions and leaf litter pools in three coast redwood forest stands on the central California coast. Monthly NPP was predicted from the CASA model using 250-meter resolution vegetation index (VI) inputs. Annual NPP was predicted to vary from 380 g·C·m-2·yr-1 to 648 g·C·m-2·yr-1 at central coast redwood sites over the years 2007 to 2010. Measured soil respiration rates at between 0.5 to 2.2 g·C·m-2·d-1 were slightly below the range of measurements previously reported for a second-growth mixed (redwood and Douglas-fir) conifer forests. Although warm monthly temperatures at the southern-most redwood forest sites evidently results in elevated stress levels to sustained redwood growth into the dry summer months of June and July, these redwood stands appear to sequester CO2 from that atmosphere into forest biomass for a net positive ecosystem carbon balance each year.
文摘This study evaluates the long-term radiometric performance of the USGS new released Landsat Collection 1 archive, including the absolute calibration of each Landsat sensor as well as the relative cross-calibration among the four most popular Landsat sensors. A total of 920 Landsat Collection 1 scenes were evaluated against the corresponding Pre-Collection images over a Pseudo-Invariant Site, Railroad Valley Playa Nevada, United States (RVPN). The radiometric performance of the six Landsat solar reflective bands, in terms of both Digital Numbers (DNs) and at-sensor Top of Atmosphere (TOA) reflectance, on the sensor cross-calibration was examined. Results show that absolute radiometric calibration at DNs level was applied to the Landsat-4 and -5 TM (L4 TM and L5 TM) by –1.119% to 0.126%. For L4 TM and L5 TM, the cross-calibration decreased the radiometric measurement level by rescaling at-sensor radiance to DN values. The radiometric changes, –0.77% for L4 TM, 0.95% for L5 TM, –0.26% for L7 ETM+, and –0.01% for L8 OLI, were detected during the cross-calibration stage of converting DNs into TOA reflectance. This study has also indicated that the long-term radiometric performance for the Landsat Collection 1 archive is promising. Supports of these conclusions were demonstrated through the time-series analysis based on the Landsat Collection 1 image stack. Nevertheless, the radiometric changes across the four Landsat sensors raised concerns of the previous Landsat Pre-Collection based results. We suggest that Landsat users should pay attention to differences in results from Pre-Collection and Collection 1 time-series data sets.
文摘The goal of this study was to determine whether climate has affected vegetation regrowth over the past decade (2000 to 2010) in post-fire forest ecosystems of the United States and Canada. Our methodology detected trends in the monthly MODerate resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) timeseries within forest areas that burned between 1984 and 1999. The trends in summed growing season EVI (composited to 8 km spatial resolution) within all burned area perimeters showed that nearly 1.6% post-fire forest area declined in vegetation greenness cover significantly (p < 0.05) over the past decade. Nearly 62% of all post-fire forest area showed a non significant EVI regrowth trend from 2000 to 2010. Regression results detected numerous significantly negative trend pixels in post-fire areas from 1994-1999 to indicate that forest regrowth has not yet occurred to any measurable level in many recent wildfire areas across the continent. We found several noteworthy relationships between annual temperature and precipitation patterns and negative post-fire forest EVI trends across North America. Change patterns in the climate moisture index (CMI), growing degree days (GDD), and the standardized precipitation index (SPI) were associated with post-fire forest EVI trends. We conclude that temperature warming-induced change and variability of precipitation at local and regional scales may have altered the trends of large post-fire forest regrowth and could be impacting the resilience of post-fire forest ecosystems in North America.
文摘The Santa Cruz Mountain range in northern California is a coastal landscape with a history of extensive forest logging and frequent large wildfires that have recently destroyed numerous residential structures at the wildland interface. Results from Landsat satellite image time-series analysis since 1984 of the study area within the Los Gatos Creek and Corralitos Creek watersheds showed that none of the severe drought periods since the 1980s have notably inhibited rapid tree and shrub regrowth rates on steep hill slopes burned recently by the 1985 Lexington Fire and the 2008 Summit Fire. In high burn severity areas of both fires, post-fire vegetation types showed a marked increase in shrub cover, mainly at the expense of evergreen tree cover. Most of these low (<3 m), dense stands of evergreen woody species have regenerated in as little as five years from bare charred ground. A combination of Landsat and Laser Altimeter (GLAS) satellite sensor data revealed that exposed south-facing slopes are presently supporting 200 to 240 Mg·ha<sup>-1</sup> of standing woody biomass on the burned areas. This study is the first of its kind to utilize a full 30-year record of Landsat vegetation index data to monitor tree and shrub regrowth after stand-replacing wildfires in California.
文摘Fog deposition is a notable component of the water budget of herbaceous-shrub ecosystems on the central and southern coastal regions of California. This paper presents an analysis of fog water deposition rates and meteorological controls in Big Sur, California. Mesh-screen fog collectors were installed the Brazil Ranch weather station sites to measure fog water during the summer seasons of 2010 and 2011. Fog deposition occurred during 73% of days recorded in 2010 and 87% of days recorded in 2011. The daily average deposition rate was 2.29 L/m2 in 2010 and 3.86 L/m2 in 2011. The meteorological variables which had the greatest influence on prediction of fog deposition were wind speed, wind direction, and the dew-point depression (difference between air temperature and dew point). Based on these results, we hypothesize that high rates of summer fog deposition help sustain the productivity of California coastal vegetation through periods of low rainfall.
文摘Aeroelastic study of flight vehicles has been a subject of great interest and research in the last several years. Aileron reversal and flutter related problems are due in part to the elasticity of a typical airplane. Structural dynamics of an aircraft wing due to its aeroelastic nature are characterized by partial differential equations. Controller design for these systems is very complex as compared to lumped parameter systems defined by ordinary differential equations. In this paper, a stabilizing statefeedback controller design approach is presented for the heave dynamics of a wing-fuselage model. In this study, a continuous actuator in the spatial domain is assumed. A control methodology is developed by combining the technique of “proper orthogonal decomposition” and approximate dynamic programming. The proper orthogonal decomposition technique is used to obtain a low-order nonlinear lumped parameter model of the infinite dimensional system. Then a near optimal controller is designed using the single-network-adaptive-critic technique. Furthermore,to add robustness to the nominal single-network-adaptive-critic controller against matched uncertainties, an identifier based adaptive controller is proposed. Simulation results demonstrate the effectiveness of the single-network-adaptive-critic controller augmented with adaptive controller for infinite dimensional systems.
文摘This paper presents a new model-reference adaptive control method based on a bi-objective optimal control formulation for systems with input uncertainty. A parallel predictor model is constructed to relate the predictor error to the estimation error of the control effectiveness matrix. In this work, we develop an optimal control modification adaptive control approach that seeks to minimize a bi-objective linear quadratic cost function of both the tracking error norm and the predictor error norm simultaneously. The resulting adaptive laws for the parametric uncertainty and control effectiveness uncertainty are dependent on both the tracking error and the predictor error, while the adaptive laws for the feedback gain and command feedforward gain are only dependent on the tracking error. The optimal control modification term provides robustness to the adaptive laws naturally from the optimal control framework. Simulations demonstrate the effectiveness of the proposed adaptive control approach.
文摘Changes in Earth＇s temperature have significant impacts on the global carbon cycle that vary at different time scales, yet to quantify such impacts with a simple scheme is traditionally deemed difficult. Here, we show that, by incorporating a tem- perature sensitivity parameter （1.64 ppm yr-1 ℃-1） into a simple linear carbon-cycle model, we can accurately characterize the dynamic responses of atmospheric carbon dioxide （CO2） concentration to anthropogenic carbon emissions and global temperature changes between 1850 and 2010 （r2 〉 0.96 and the root-mean-square error 〈 1 ppm for the period from 1960 onward）. Analytical analysis also indicates that the multiplication of the parameter with the response time of the atmospheric carbon reservoir （-12 year） approximates the long-term temperature sensitivity of global atmospheric CO2 concentration （-15 ppm ℃ 1）, generally consistent with previous estimates based on reconstructed CO2 and climate records over the Little Ice Age. Our results suggest that recent increases in global surface temperatures, which accelerate the release of carbon from the surface reservoirs into the atmosphere, have partially offset surface carbon uptakes enhanced by the elevated atmo- spheric CO2 concentration and slowed the net rate of atmospheric CO2 sequestration by global land and oceans by -30% since the 1960s. The linear modeling framework outlined in this paper thus provides a useful tool to diagnose the observed atmospheric CO2 dynamics and monitor their future changes.
文摘Biopolymer-bound Soil Composites(BSC),are a novel bio-based construction material class,produced through the mixture and desiccation of biopolymers with inorganic aggregates with applications in soil stabilization,brick creation and in situ construction on Earth and space.This paper introduces a mixture design methodology to produce maximum strength for a given soil-biopolymer combination.Twenty protein and sand mix designs were investigated,with varying amounts of biopolymer solution and compaction regimes during manufacture.The ultimate compressive strength,density,and shrinkage of BSC samples are reported.It is observed that the compressive strength of BSC materials increases proportional to tighter particle packing(soil dry bulk density)and binder content.A theory to explain this peak compressive strength phenomenon is presented.
文摘This paper is focused on adaptively controlling a linear infinite-dimensional system to track a finite-dimensional reference model.Given a linear continuous-time infinite-dimensional plant on a Hilbert space with disturbances of known waveform but unknown amplitude and phase,we show that there exists a stabilizing direct model reference adaptive control law with the properties of certain disturbance rejection and robustness.The plant is described by a closed,densely defined linear operator that generates a continuous semigroup of bounded operators on the Hilbert space of states.The central result will show that all errors will converge to a prescribed neighborhood of zero in an infinitedimensional Hilbert space.The result will not require the use of the standard Barbalat’s lemma which requires certain signals to be uniformly continuous.This result is used to determine conditions under which a linear infinite-dimensional system can be directly adaptively controlled to follow a reference model.In particular,we examine conditions for a set of ideal trajectories to exist for the tracking problem.Our results are applied to adaptive control of general linear diffusion systems described by self-adjoint operators with compact resolvent.
