510 research outputs found
Infrared ship signature analysis and optimisation
No full textThe last decade has seen an increase in the awareness of the infrared signature of naval ships. New ship designs show that infrared signature reduction measures are being incorporated, such as exhaust gas cooling systems, relocation of the exhausts and surface cooling systems. Hull and superstructure are cooled with dedicated spray systems, in addition to special paint systems that are being developed for optimum stealth. This paper presents a method to develop requirements for the emissivity of a ship's coating that reduces the contrast of the ship against its background in the wavelength band or bands of threat sensors. As this contrast strongly depends on the atmospheric environment, these requirements must follow from a detailed analysis of the infrared signature of the ship in its expected areas of operation. Weather statistics for a large number of areas have been collected to produce a series of 'standard environments'. These environments have been used to demonstrate the method of specifying coating emissivity requirements. Results are presented to show that the optimised coatings reduce the temperature contrast. The use of the standard environments yields a complete, yet concise, description of the signature of the ship over its areas of operation. The signature results illustrate the strong dependence of the infrared signature on the atmospheric environment and can be used to identify those conditions where signature reduction is most effective in reducing the ship's susceptibility to detection by IR sensors
Upper mantle structure from body-wave coda and amplitudes
No full textThe last decade has seen a large increase in the amount of high-quality data from a growing
number of digitally operating seismic stations. Both short- and long-period data are
reported on a regular basis to central data centres. As global seismology is hampered by the
unequal distribution of stations and earthquakes, extracting as much as possible information
from the available data is important. However, only a relatively small part of the growing
data volume is used on a more or less routine basis. New sources of information from the
seismogram may add independent constraints on and provide a higher resolution of Earth
structure.
The most widely used parts of the seismogram are the P-wave travel time and the longperiod
surface wave train. The travel time of the (mostly short-period) P-wave is used on a
large scale to invert for Earth structure (Spakman 1991; Vandecar 1991; Van der Hilst &
Engdahl 1991), Recently, also the S-wave travel time is used in tomographic inversions
(e.g., Zielhuis 1988). On the low-frequency end of the spectrum, long-period surface wave
forms are inverted for mantle velocity structure (e.g., Woodhouse & Dziewonski 1984;
Snieder 1988). Recent studies include the long-period S-waves in the wave form modeling
using modal summation (Nolet 1990: Zielhuis 1992). The results of Li & Tanimoto (1991)
show that it is still prohibitively time-eonsuming to include also the long-period P-wave in
this process.
This leaves large parts of the seismogram unused in inversion procedures. Before these
can be included in any inversion process, their information content and relation to Earth
structure must be established (e.g.• wave propagation in a laterally homogeneous or heterogeneous
Earth model). The main goal of the research presented in this thesis is to determine
the information content of parts of the seismogram that are not frequently used and, if
possible, to develop methods to extract this information
UV missile plume signatures
No full textAs a result of the deployment of UV missile warning systems, recent years have seen an increasing interest in threat assessment in the UV band. Unfortunately, due to the different nature of the physical processes that are needed to describe a missile signature in the UV, available codes for the IR can not be applied. As a result, the development of a UV missile plume signature model was initiated. This paper presents a model for the prediction of UV missile plume signatures, that takes into account relevant physical mechanisms in a missile plume. The model is based on first principles, predicting the radiance from CO-O chemiluminescence and hot particles in the plume, which are the dominant sources of radiation in the UV wavelength band considered. Scattering of radiation on particles in the plume can be important for particle-rich propellants and is accounted for in the code. The multiple scattering algorithm has been set up to handle any number of directions in an axi-symmetric medium; the algorithm presents a novel way of solving the radiative transfer problem. Several examples are shown, to illustrate scattering processes in missile plumes. A number of validation tests are presented to show the model's performance. At this stage, comparisons with real data are under progress
Ship transport of CO2 – breaking the CO2-EOR deadlock
No full textAbstractThe North Sea contains the larger part of the storage capacity in North West Europe. Countries around the North Sea currently focus their attention on developing that capacity for the CCS demonstration projects. It is generally assumed that a second wave of CCS projects will further develop storage in the North Sea. However, a major hurdle is the development of long-distance pipelines. A requirement for the construction of a ‘backbone’ pipeline is the availability of a sufficient volume of CO2, with a firm commitment on the duration of supply of CO2. Especially for EOR purposes a CO2 pipeline is not attractive, due to continuously decreasing demand for CO2 after an initial peak.Transport by ship can provide a solution, because of its inherent flexibility in combining CO2 from several sources, each too small to warrant a pipeline, to one or more storage locations. This paper describes the case for ship transport of CO2 to North Sea oil fields, especially in the early phases of the development of CCS in Europe, providing the cross-benefit that will increase the lifetime of oil fields and, at the same time, provide the required commercial case for CO2 capture and transport. This will help develop CCS industry, which will help EU Member States to meet their CO2 emission reduction targets
CO2 storage development: status of the large European CCS project with EEPR funding
No full textThis paper presents an overview of the CO2 storage element of the projects that are part of the European CCS Demonstration Project Network, an FP7 funded project to support the knowledge exchange among the CCS projects that have received funding under the EEPR framework. These projects include the ROAD project (The Netherlands) and the Don Valley project (UK). The Hontomín project (Spain) can be regarded as the third project, as it was developed as the research site for the Compostilla project in Spain; the Compostilla project, also a beneficiary of EEPR funds, was discontinued in 2013 after completing FEED studies. The Sleipner project joined the Network in 2011 and provided its experience and expertise to the EEPR funded projects. Together, the projects in the Network cover a wide range of storage options, from a depleted gas field to saline sandstone and carbonate formations. The ROAD project uses a compartment of an offshore depleted gas field, and the Don Valley project is developing an offshore saline aquifer. The Hontomín site, dedicated to research, uses an onshore carbonate reservoir. This paper gives an overview of the storage solutions developed or under development by these project
Aerosol production in the surf zone and effects on IR extinction
No full textThe aerosol production in the surfzone, as determined from measurements, at two sites along the Califomia coast is presented. The data used were collected during three EOPACE (Electro-Optical Propagation Assessment in Coastal Environments) measurement campaigns in 1996 and 7997. Particle counters were deployed at both the end and the base of two piers which extended into the ocean, beyond the surf zone. For winds from the sea, a clear increase in aerosol concentration was measured, between the particle counters at the end and the base of the piers. Aerosol concentrations were measured at the base of the piers at three heights, which allowed for the estimation of the aerosol production in the surf zone. Taking into account the different whitecap ratios, the surf zone aerosol source function derived from the data compares well with previously reported open-ocean source functions, in agreement with the common bubble (film and jet drops) origin. Wind speeds measured during the experiments were up to about 9 m/s; therefore, the source function presented here applies to the bubble part of the source spectrum only. Infra-red extinction coefficients were computed from the aerosol concentrations, using a Mie scattering code. Extinction values may be up to two orders of magnitude larger than in the unperturbed oceanic air mass; the vertical gradients in extinction are also much stronger than those reported for open-ocean conditions. A simple aerosol dispersion model, using observed surf zone aerosol production rates, predicts that air masses up to several km from the surf zone may be significantly affected by the surf-produced aerosol. For winds from land, this proves the importance of the surfzone in assessing the performance of electro-optical systems in coastal areas
Infrared ship signature prediction, model validation and sky radiance
No full textThe increased interest during the last decade in the infrared signature of (new) ships results in a clear need of validated infrared signature prediction codes. This paper presents the results of comparing an in-house developed signature prediction code with measurements made in the 3-5 μm band in both clear-sky and overcast conditions. During the measurements, sensors measured the short-wave and long-wave irradiation from sun and sky, which forms a significant part of the heat flux exchange between ship and environment, but is linked weakly to the standard meteorological data measured routinely (e.g., air temperature, relative humidity, wind speed, pressure, cloud cover). The aim of the signature model validation is checking the heat flux balance algorithm in the model and the representation of the target. Any uncertainties in the prediction of the radiative properties of the environment (which are usually computed with a code like MODTRAN) must be minimised. It is shown that for the validation of signature prediction models the standard meteorological data are insufficient for the computation of sky radiance and solar irradiation with atmospheric radiation models (MODTRAN). Comparisons between model predictions and data are shown for predictions computed with and without global irradiation data. The results underline the necessity of measuring the irradiation (from sun, sky, sea or land environment) on the target during a signature measurement trial. Only then does the trial produce the data needed as a reference for the computation of the infrared signature of the ship in conditions other than those during the trial
Value chain analysis of CO2 storage by using the EccoTool: A case study of the Dutch offshore
No full textA detailed analysis is presented of the short and medium term development of CCS in The Netherlands. Scenarios for CCS development were constructed by combining the most recent estimates of offshore storage capacity, for both depleted gas fields and saline formations, with expected timing and volumes of captured CO2 from two industrialised regions, the Rotterdam harbour area and the Eemshaven area. Individual emitters in both regions were approached to obtain realistic growth profiles for captured volumes. This paper explores the cost of transport and offshore storage of CO2 and explores the benefits of the two regions in joining their storage efforts. Further work is ongoing and will focus on the CCS value chain, to provide the emitters with insight in the cost structure of transport and storage. Furthermore, the study will provide input during the development of a national CCS implementation plan
MiReCOL: Developing Corrective Measures for CO2 Storage
No full textAbstractCO2 capture, transport and storage (CCS) has the potential to significantly reduce the carbon emission that follows from the use of fossil fuels in power production and industry. Integrated demo-scale projects are currently being developed to demonstrate the feasibility of CCS and the first such projects are expected to start operating in Europe under the Storage Directive in the period 2015 – 2020. As part of the license application, these projects must develop a corrective measures plan, which describes the measures that can be taken when the CO2 in the subsurface behaves in an unexpected way. The MiReCOL project supports the development of corrective measures plans and helps building confidence in the safety of deep subsurface CO2 storage by providing a toolbox of techniques to mitigate and/or remediate undesired migration of CO2. MiReCOL aims to support the dialogue between CCS project operators and regulators by providing a clear description of the scope and feasibility of corrective measures
- …
