Bulk Transfer Research Articles

Convex parameter estimator for grey-box models, applied to characterise heat flows in greenhouses

An algorithm is presented to identify model parameters in grey-box models. The solver is convex, so the global optimum is guaranteed. The method is applied to estimate bulk transfer coefficients in greenhouses from easily monitored data. This model covers the most important processes, such as conduction losses to the environment, heat exchange with neighbouring compartments, heating from the sun and lighting installations, and ventilation losses. Screen positions are also included in the model. Each process is parameterised, so that the specific situation of each greenhouse can be identified. Greenhouse experiments are often repeated in the same greenhouse or performed in parallel. If some model parameters are assumed to remain identical in these experiments, this can be incorporated in the optimiser making it more robust. The estimator is exemplified using measurements from two compartments in a greenhouse; one equipped with LED lighting, the other equipped with HPS lighting. It showed that effective conduction parameters for the greenhouse and screens were similar to values found in literature (5.8 and 5 W m−2 K−1, respectively). The model also predicted that both lighting systems provide the same amount of sensible heat at the height of the plants, despite the HPS system consuming 43% more energy. A vertical temperature measurement confirmed that both lighting systems produced the same amount of heat at the height of the plants. The LED system dispersed heat more evenly over height, while the HPS system heated the upper layers more.

Effects of persistent wind speeds on turbulent fluxes in the water-atmosphere interface

Understanding air-water interactions is critical to establishing the role of inland water bodies in regulating local and regional weather so that more accurate parameterizations of flux exchange in numerical weather models can be achieved. Wind-induced mixing actively alters environmental variables, leading to changes in turbulent exchanges of latent heat (LE) and sensible heat (H) fluxes above water surfaces. It remains extensively unexplored as to how winds in different wind speed ranges modulate coupling of different variables, which in turn regulates LE and H. Here, we analyze 28-month eddy covariance data collected over a large reservoir. We categorize the dataset into four wind classes with different wind speed ranges: I ( 5.13 m s−1). The enhanced mechanical mixing promotes LE and H with the increased wind classes due to the increased sensitivity to Δe and ΔT despite the reduced role of atmospheric stability. Hence, the highest LE and H occur in IV, under moderately unstable and stable conditions. Overall, the bulk transfer coefficients behave similarly under a certain stability condition across all wind classes while the similarity theory systematically underestimates their magnitudes. These results have important applications in improving parameterization schemes to estimate fluxes over water surfaces in numerical models.

Bulk transfer of blood and its component: A single-center experience after 2 years of its implementation

Background and Objectives: BTS in India is highly decentralized and lack many vital resources. National blood policy also depicted safe and adequate blood supply. An Important initiative that can lead to increased efficiency of blood transfusion services (BTS) in our country namely bulk transfer of blood permitting the exchange of blood among licensed blood bank was taken by NACO in the year 2015. In this study we tried to understand the impact of bulk transfer policy in bridging the gap between demand and supply and also prevent the wastages of precious blood resources. Material and Methods: Retrospective analysis of demand-supply of PCV and PC was done for the year 2016-2017. The same done again after implementation of bulk transfer policy for the year 2017-2018 just starting phase (few blood banks adopted) and for the year 2018-2019 after many blood banks taken up bulk transfer. Results: Before implementation of bulk transfer policy only 54.63% patients got red cell concentrate for transfusion and 38.35% patients got platelet concentrate. Supply increases to 68.31% and 69.41% respectively and hence reduces the wastage. Conclusion: Bulk transfer amendment is of great help to prevent wastages of precious blood resources, and hence can win the trust of society and increase voluntary blood donation.

The role of carbon dots - derived underlayer in hematite photoanodes.

Hematite is a promising candidate as photoanode for solar-driven water splitting, with a theoretically predicted maximum solar-to-hydrogen conversion efficiency of ∼16%. However, the interfacial charge transfer and recombination greatly limits its activity for photoelectrochemical water splitting. Carbon dots exhibit great potential in photoelectrochemical water splitting for solar to hydrogen conversion as photosensitisers and co-catalysts. Here we developed a novel carbon underlayer from low-cost and environmental-friendly carbon dots through a facile hydrothermal process, introduced between the fluorine-doped tin oxide conducting substrate and hematite photoanodes. This led to a remarkable enhancement in the photocurrent density. Owing to the triple functional role of carbon dots underlayer in improving the interfacial properties of FTO/hematite and providing carbon source for the overlayer as well as the change in the iron oxidation state, the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced, and consequently led to a remarkable enhancement in the photocurrent density. The results revealed a substantial improvement in the charge transfer rate, yielding a charge transfer efficiency of up to 80% at 1.25 V vs. RHE. In addition, a significant enhancement in the lifetime of photogenerated electrons and an increased carrier density were observed for the hematite photoanodes modified with a carbon underlayer, confirming that the use of sustainable carbon nanomaterials is an effective strategy to boost the photoelectrochemical performance of semiconductors for energy conversion.

Bulk Savings for Bulk Transfers: Minimizing the Energy-Cost for Geo-Distributed Data Centers

With the fast proliferation of cloud computing, major cloud service providers, e.g., Amazon, Google, Facebook, etc., have been deploying more and more geographically distributed data centers to provide customers with better reliability and quality of services. A basic demand in such a geo-distributed data center system is to transfer bulk volumes of data from one data center to another. Geographic distribution and large delay-tolerance of such inter-data-center bulk data transfers provide cloud service providers opportunities to optimize the operating cost. Most existing studies on inter-data-center bulk data transfers focus on minimizing the network bandwidth cost. However, the energy-cost of the bulk data transfers, which also accounts for a large proportion of operating cost in the data centers, still remains unexplored. This is an important problem, especially in the multi-electricity-market environment, where the electricity price exhibits both spatial and temporal diversities. In this paper, we systematically study the problem of how to route and schedule inter-data-center bulk data transfers to minimize the energy-cost for geo-distributed data centers. We model this problem as a min-cost multi-commodity flow problem and develop an efficient two-stage optimization method to solve it. Extensive evaluations with real-life inter-data-center network and electricity prices show that our method brings significant energy-cost savings over existing bulk data transfer methods.

Biological role of mycorrhizal fungi on the assimilation and transportation of carbon and nitrogen to Anacamptis palustris and Anacamptis laxiflor.

Fungal is a physiological trail and its understanding in the assimilation with the transfer of carbon (C) cum nitrogen (N) or (C/N) to orchid-seedlings have not been determined. Labelled stable isotopes 13C and 15N were used to plan the flow of C and N between orchid plants and mycorrhizal connotations in-terms of bulk transfer for C/N. This study attends to comprehend the mechanism, supporting mycorrhizal fungi which influences on orchid-seedling growth. Determined integration and transfer of C/N from amino acids (AA), ammonium nitrate (NH4NO3) and sugar for orchid-plant may lead to understand these mechanisms. This current study tries to estimate the importance of organic compounds as a source for C/N over the inorganic-NH4NO3. Generally, after begging of germination and when it is found to be associated to the nutrient resource, organic compound enhance the biomass accumulation of two orchid species. AA significantly increase the mass of 13C assimilated by two species. With amino acids the concentration of 13C in two species was greater than with NH4NO3 and sugar. At another phase, amount of 15N content shoots was a higher value in Anacamptis laxiflora shoots assimilated substantially additional of 15N with NH4NO3 plus sugar compared with ammonium nitrate only. This study showed that two terrestrial orchids species are reliant on organic compounds as a source of carbon and nitrogen more than inorganic compounds.

Cost-Efficient Scheduling of Bulk Transfers in Inter-Datacenter WANs

With the quick growth of traffic between data centers, inefficient transfer scheduling in inter-datacenter networks can lead to a huge waste of bandwidth thus significant bandwidth cost. Previous work have explored different ways, such as software-defined WANs and dynamic pricing mechanisms, to overcome the inefficiency of inter-datacenter networks. However, there is a big challenge in addressing the fundamental conflicts between the deadline-aware transfer scheduling and minimizing the bandwidth cost. Unlike existing efforts that schedule inter-datacenter transfers under fixed link capacities, wherein some deadlines are violated and the service quality is degraded, we aim to finish all the transfers on time with as little bandwidth as possible to minimize the bandwidth cost. We take into account the variation of bandwidth price and the deadline requirements of services, and formulate the problem of cost-efficient scheduling of bulk transfers with deadline guarantee, which is shown to be NP-hard. Benefitting from the relax-and-round method, we propose a progressively-descending algorithm (PDA) to schedule bulk transfers and meet the above goals with a guaranteed approximation ratio. We apply our algorithm in a bulk transfer scheduler, Butler, and build a small-scale testbed to evaluate its efficiency. Both large-scale simulation and testbed experiment results validate the ability of our scheme on cutting down the bandwidth cost. Compared with existing approaches, it reduces up to 60% bandwidth cost and increases the network utilization by up to 140%.

Efficient inter-datacenter bulk transfers with mixed completion time objectives

Bulk transfers from one to multiple datacenters can have many different completion time objectives ranging from quickly replicating some k copies to minimizing the time by which the last destination receives a full replica. We design an SDN-style wide-area traffic scheduler that optimizes different completion time objectives for various requests. The scheduler builds, for each bulk transfer, one or more multicast forwarding trees which preferentially use lightly loaded network links. Multiple multicast trees are used per bulk transfer to insulate destinations that have higher available bandwidth and can hence finish quickly from congested destinations. These decisions–how many trees to construct and which receivers to serve using a given tree–result from an optimization problem that minimizes a weighted sum of transfers’ completion time objectives and their bandwidth consumption. Results from simulations and emulations on Mininet show that our scheduler, Iris, can improve different completion time objectives by about 2.5 × .

Dynamic response of land–atmosphere-coupling parameters to precipitation in the sparse-vegetated Asian summer monsoon transition zone

Land–atmosphere-coupling parameters usually relate to particular climatic conditions and seldom consider the influence of the inter-annual variability of precipitation. This results in large uncertainty in the estimation of land-surface physical variables. In the current study, observed data for five land–atmosphere-coupling parameters (surface albedo, soil thermal conductivity, aerodynamic roughness length, and the bulk transfer coefficients of momentum and sensible heat) were analysed and related to the inter-annual variability of precipitation on the Loess Plateau, China, from April 2006 to March 2013. This is an area with sparse vegetation. The results demonstrate that the land–atmosphere-coupling parameters are very sensitive to the inter-annual variability of precipitation. The surface albedo increased with increasing duration of snow cover. The other four parameters increased when annual effective precipitation (yearly sum of daily rainfall > 4 mm or daily snowfall > 0.1 mm) increased, and the sensitivity decreased when annual effective precipitation increased. Empirical relations between the five land–atmosphere-coupling parameters and the inter-annual variability of precipitation were derived via regression, with R2 values of 0.67, 0.85, 0.93, 0.99, and 0.95, respectively. The land-surface physical variables calculated with dynamic land–atmosphere-coupling parameters (considering the inter-annual variability of precipitation) were much closer to the observed data than those calculated with static land–atmosphere-coupling parameters. The relative error was reduced by > 80% in years with low precipitation. This indicates that the inter-annual variability of precipitation has a significant impact on the land-surface physical variables. The results demonstrate that land–atmosphere-coupling parameters, which take into account inter-annual variability of precipitation, provide a more realistic representation of the land surface.

Estimation of Surface Heat Fluxes Over the Central Tibetan Plateau using the Maximum Entropy Production Model

AbstractSurface heat fluxes over the central Tibetan Plateau have been estimated using the maximum entropy production (MEP) model with the surface energy balance and the observation data from the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX‐III). The MEP surface heat fluxes are highly correlated with those of the TIPEX‐III observations. The agreement between the MEP and TIPEX‐III heat fluxes is higher when the observed surface energy balance closure is better. The errors of the MEP heat fluxes are smaller compared to those of the fluxes derived from the bulk transfer method, the Land Data Assimilation Systems, and the Simple Biosphere Model version 2 reported in the previous studies. The values of MEP sensible and latent heat fluxes tend to be less than those of the previous bulk heat fluxes. Thus, the MEP model can reasonably estimate surface heat fluxes over the central Tibetan Plateau.

Comparison of Heat Flux Observation at Three Different Locations around Bandung, West Java

We observed heat flux profiles at three different locations around Bandung, West Java. Heat flux values were calculated using the covariance method with the vertical flow and potential air temperature fluctuation parameters. Observations have shown diurnal patterns in the three observation locations. Increasing heat flux during morning time flux on all three location shows similar pattern, but decreasing heat flux on the afternoon varies between locations. Urban residential area of Dago shows the most distinct pattern, with a rapid decrease in the afternoon and also after midnight. We also compared observed heat flux data with estimate values using the Bulk Parameterization method. We found that the estimated heat flux was not able to produce values in accordance with the observation data. Wind shear factor and inadequate implementation of the Bulk Parameterization method were thought to causing poor estimation of surface heat flux in Bandung. Improvements in this method, especially on the bulk transfer coefficient and surface skin temperature, are necessary to get better estimation result.

Steady-State Analysis of Buffer Occupancy for Different Forwarding Strategies in Mobile Opportunistic Network

We perform a study on the buffer occupancy 1 1 The term buffer occupancy refers to the amount (or number) of data (or packets) present in the buffer. We shall be using the terms buffer occupancy and system size interchangeably as deemed fit. and its steady-state properties in a mobile opportunistic network (MON) for different forwarding strategies. Nodes in MON adhere to replication based strategy in order to ensure reliable delivery. Such replications occur in bulks during intermittent and very short contact events, which often lead to buffer congestion in the relay nodes, thereby affecting the network performance. The state-of-the-art on buffer management in MON relies on local information exchange to measure buffer occupancy, which leads to overhead. Therefore, to find the average buffer occupancy, we first study the aggregated bulk transfer size using real-life contact traces and find that it follows a log-normal distribution. Since the contact rate has been observed to follow a Poisson distribution, we model the packet arrival process in each node as a compound Poisson process. Furthermore, the departure process is modeled as packets dropped due to time-to-live expiry, which is shown to have an exponential distribution. Using the above model, we derive the steady-state probability distribution of buffer occupancy of an arbitrary node for three different classes of replication scheme, viz., epidemic routing, probabilistic routing, and time-varying probabilistic routing. The results of this paper help in assessing how fast a node buffer gets depleted under different routing algorithms, which will help in designing better buffer management techniques and routing algorithms.

Estimation of Sensible Heat Flux and Atmospheric Boundary Layer Height Using an Unmanned Aerial Vehicle

In this work, sensible heat flux estimated using a bulk transfer method was validated with a three-dimensional ultrasonic anemometer or surface layer scintillometer at various sites. Results indicate that it remains challenging to obtain temperature and wind speed at an appropriate reference height. To overcome this, alternative observations using an unmanned aerial vehicle (UAV) were considered. UAV-based wind speed and sensible heat flux were indirectly estimated and atmospheric boundary layer (ABL) height was then derived using the sensible heat flux data. UAV-observed air temperature was measured by attaching a temperature sensor 40 cm above the rotary-wing of the UAV, and UAV-based wind speed was estimated using attitude data (pitch, roll, and yaw angles) recorded using the UAV’s inertial measurement unit. UAV-based wind speed was close to the automatic weather system-observed wind speed, within an error range of approximately 10%. UAV-based sensible heat flux estimated from the bulk transfer method corresponded with sensible heat flux determined using the eddy correlation method, within an error of approximately 20%. A linear relationship was observed between the normalized UAV-based sensible heat flux and radiosonde-based normalized ABL height.

Distribution and Variation of the Surface Sensible Heat Flux Over the Central and Eastern Tibetan Plateau: Comparison of Station Observations and Multireanalysis Products

AbstractSurface sensible heat fluxes (SH) over Tibetan Plateau (TP) dictate the seasonal conversion, onset and maintenance of the Asian monsoon. Spatiotemproal variability in SH over central and eastern TP (CETP) from reanalysis products (i.e., JRA55, ERA‐Interim, NCEP1, and NCEP2) and derived using bulk transfer approximations applied to observations is characterized for all seasons during 1980–2015 and is diagnosed in the context of two important drivers of variability: wind speed and land‐air temperature difference (Tg‐Ta). In the climatological mean, SH from observations increases from east to west and exhibits obvious seasonality with highest value in spring and lowest in winter. Declines in SH prior to 2000 as manifest in the observations appears to have resulted from changes in wind speeds, and the subsequent recovery is attributable to increases in both wind speeds and air‐surface temperature gradients. The intercomparison shows that ERA‐Interim exhibits greatest accord with observations in terms of the climatological distribution and seasonality, and all reanalyses exhibit some aspects of the temporal variability and long‐term trends as manifest in the observations. However, the root causes of the long‐term variability in SH as manifest in the reanalysis products are not consistent with inferences derived from the observations.

Tuning perovskite oxides by strain: Electronic structure, properties, and functions in (electro)catalysis and ferroelectricity

Abstract Complex oxides, such as ABO3 perovskites, are an important class of functional materials that exhibit a wide range of physical, chemical, and electrochemical properties, including high oxygen electrocatalytic activity, tunable electronic/ionic conductivity, and ferroelectricity. When complex oxides are engineered as thin films, their chemical and physical properties can be modified to be markedly different from their bulk form, providing additional degrees of freedom in materials design. In this review, we survey the landscape of strain-induced design of complex oxides in the context of oxygen electrocatalysis and ferroelectricity. First, we identify the role of strain in influencing oxide electronic properties, driven by the combination of modification of B O bond length and octahedral distortion in perovskites. We describe electronic structure parameters, such as the O 2p-band center, that quantitatively capture these electronic changes, highlighting the broad influence of the O 2p-band center on surface reactivity (oxygen adsorption and dissociation energy) and bulk defect energetics (oxygen vacancy formation and migration energy). Motivated by the promise of the influence of strain on material properties relevant for oxygen electrocatalysis and ferroelectricity, we describe the advances in state-of-the-art thin-film fabrication and characterization that have enabled a high degree of experimental control in realizing strain effects in oxide thin-film systems. In oxygen electrocatalysis, leveraging strain has not only resulted in activity enhancements relative to bulk unstrained material systems but also revealed mechanistic influences of oxide phenomena, such as bulk defect chemistry and transfer kinetics, on electrochemical processes. Similarly for ferroelectric properties, strain engineering can both enhance polarization in known ferroelectrics and induce ferroelectricity in material systems that would be otherwise non-ferroelectric in bulk. Based on understanding of a diverse range of perovskite functionalities, we offer perspectives on how further coupling of strain, oxygen electrocatalysis, and ferroelectricity opens up pathways toward the emergence of novel device design features with dynamic control of increasing complex chemical and high-performance electronic processes.

Significant differences exist in lake-atmosphere interactions and the evaporation rates of high-elevation small and large lakes

Lakes impact atmosphere boundary layer processes and are thus important for catchment scale climate modeling and regional water and heat budgets. To explore the differences in lake-atmosphere interaction parameters, meteorological variables and turbulent heat fluxes in small and large water bodies, we collected eddy covariance observations and meteorological data during ice-free periods of the Lake small Nam-Co (“small lake”) in 2012–2013 and Lake Nam-Co (“large lake”) in 2015–2016 on the Tibetan Plateau. Significant differences exist in their lake-atmosphere interaction processes due to differences in their inherent attributes and environmental backgrounds. Relative to the “small lake”, the maximum surface temperature of the “large lake” in summer is approximately 3 °C lower; “large lake” also has a larger wind speed, a higher monthly average air temperature and delayed peaks of the seasonal variation of water and air temperature. The typical values of the roughness length and standard bulk transfer coefficient for momentum are approximately 80% and 21% higher, respectively, for the “large lake”. The typical values of the roughness lengths for heat and water are one order of magnitude lower in the “large lake” while the corresponding standard bulk transfer coefficients are only 7% lower. The latent and sensible heat fluxes of the two lakes have quite different seasonal variations, with evaporation peaking in November for the “large lake” and in June for the “small lake”. The estimated evaporation during the ice-free season of the “large lake” (approximately 981±18 mm) is also higher than that (812 mm) of the “small lake” and this is mainly related to the observed lower Bowen ratio in the “large lake”.

Energy partitioning of greenhouse cucumber based on the application of Penman-Monteith and Bulk Transfer models

Partitioning between latent (LET) and sensible (H) heat fluxes is critical in improving the greenhouse crops irrigation scheduling and microclimate. By applying the Bulk Transfer (BT) and Penman-Monteith (PM) models, the energy fluxes in different growing stages of the cucumber crop were determined in a Venlo-type greenhouse. The application of the BT and PM models is constrained by accurate parameterizations of canopy resistance (rc) and aerodynamic resistance (ra). In this paper, we measured micrometeorological data, crop growth index and LET during cucumber growing seasons in spring and autumn of 2016. The rc was modelled with stomatal conductance of cucumber leaves and validated with actual measurement of LET by lysimeters. The results showed that rc varied from 35 s m−1 during the day to 500 s m−1 at night in spring season, whilst it ranged from 40 s m−1 during the day to 1000 s m−1 at night in autumn season. Comparison of rc estimated by the PM and the BT models demonstrated that the rc estimated by the two methods were similar and highly correlated for both seasons. During the spring season, the PM and the BT models gave the determination coefficients (R2) of predicted hourly LET equal to 0.94 and 0.83, whereas during the autumn season, the values were 0.94 and 0.76, respectively. The average root mean square errors (RMSE) of measured and predicted hourly LET were 96.97 and 74.74 W m-2 for the spring and autumn seasons for PM model, respectively. In contrast, the BT model gave RMSE of measured and predicted hourly LET of 82.47 and 69.14 W m-2, for spring and autumn, respectively. The results also depicted that the simplified energy balance approach was a feasible alternative to partition the energy fluxes in the greenhouse. The predictions made in this study would be an easy and relatively accurate way to partition greenhouse cucumber energy fluxes and thus, scientifically plan the irrigation schedule. In conclusion, this study provides scientific basis for optimizing efficient water-saving irrigation, development of a suitable irrigation scheduling and improving crop water use efficiency in the greenhouse, and consequently, more energy savings by avoiding excessive water application and thereby the objective of having improved and satisfactory yield and higher economic returns can be achieved.

Estimation of the surface heat transfer coefficient over the east-central Tibetan Plateau using satellite remote sensing and field observation data

The bulk transfer method is commonly used to calculate the surface sensible heat (SSH) flux in climatology and in the numerical model, but in the calculation, the value of the bulk transfer coefficient for heat (Ch) is generally regarded as a fixed value (e.g., 0.004 in the Tibetan Plateau), without considering its seasonal variations and regional differences. In this study, a new method for upscaling data from the local to regional scale is proposed and tested to estimate Ch over the east-central Tibetan Plateau (TP) using the latest version Global Inventory Modeling and Mapping Studies (GIMMS), Normalized Difference Vegetation Index (NDVI) dataset, and micrometeorological observations collected at four field sites. Results suggest that the proposed method is capable of reflecting the variations in Ch at the regional scale in a climatic context. It is a relatively reliable way of estimating the value of Ch using satellite remote sensing data and field observations. Then, the monthly values of Ch and the SSH flux at 70 China Meteorological Administration (CMA) stations on the east-central TP during the period 1982–2012 are estimated. Results show that the value of Ch ranges from 0.0025–0.0050, with obvious seasonal variations and spatial differences. Because the surface vegetation coverage in the southeastern part of the TP is better than that in the north-central part, the values of Ch are higher than that in the north-central part of the TP throughout the year. The SSH flux also shows obvious seasonal variations and spatial differences, which is strongest in spring, followed by summer and autumn, and smallest in winter. Furthermore, the seasonal mean SSH has undergone a significant interdecadal transition in the early 2000s, from the previous weakening trend to the strengthening trend. Based on the results of this study, the values of Ch obtained from a limited number of local field observations on the plateau can be applied to more CMA stations at the regional scale. Such a method can improve the calculation accuracy of the SSH flux over the TP and aid studies of plateau meteorology and climatology.

Dye-sensitized solar cell utilizing TiO2–sulphur composite photoanode: influence of sulphur precursor content

TiO2–sulphur composite films have been prepared and employed as photoanode of dye-sensitized solar cell (DSSC). The influence of sulphur precursor content in terms of thiourea concentration on the structural and optical properties of the sample has been investigated. The anatase and sulphur phases exist in the composite. The secondary phases, namely SO3 and Ti3S4, also present in the composite. The 0.3 M sample possesses the highest reflection and absorption in visible region. Raman characterization reveals that the peak at 474 cm−1 corresponds to the A1g symmetric stretching mode of sulphur. The effect of the sulphur precursor concentration on the performance parameters of the device has also been investigated. The DSSC utilizing the sample with 0.3 M thiourea demonstrates the highest power conversion efficiency, η of 1.80% due to the highest dye loading, the lowest bulk and charge transfer resistance and the longest carrier lifetime. Combining TiO2 with sulphur in composite form was found as an effective way of enhancing the efficiency of the DSSC.

Comparison of empirical and predicted ultraviolet aircraft signatures

In light of the potential threat to aircraft from missiles using ultraviolet (UV) wavebands, it is important to understand the signature of an aircraft and how this can be predicted. This study compares empirical UV signature data to modeled data from camouflage electro-optical simulation (CAMEOSIM) to determine how well the contrast between the object and the background can be predicted using local knowledge of the atmosphere. CAMEOSIM uses the standard moderate resolution atmospheric transmission (MODTRAN) model to estimate the radiative transfer through the atmosphere. Both MODTRAN and CAMEOSIM are well validated in visible and infrared wavebands, and MODTRAN can accurately predict UV radiative transfer. Unfortunately, the work so far has concentrated on bulk transfer to describe the sky background in the UV where the aircraft scene is typically a negative contrast “hole” in a positive sky background. Importantly, path-to-path scattering is a key consideration in this scene since it is this that will tend to blur the edges of an object and reduce the contrast associated with it. A developed understanding of the limitations is required. It is determined that prediction is possible up to the ranges of 5 km. The local visibility (in km) is required for this prediction.