•Optimal waste heat recovery technology for offshore platforms.•Organic Rankine cycle, air bottoming cycle and steam Rankine cycle as waste heat recovery units.•Multi-objective design-point ...optimization approach to compare the three alternatives.•Three objective functions considered: yearly CO2 emissions, weight and net present value.•Case study: Draugen offshore oil and gas platform in the Norwegian Sea.
This article aims at finding the most suitable waste heat recovery technology for existing and future offshore facilities. The technologies considered in this work are the steam Rankine cycle, the air bottoming cycle and the organic Rankine cycle.
A multi-objective optimization approach is employed to attain optimal designs for each bottoming unit by selecting specific functions tailored to the oil and gas sector, i.e. yearly CO2 emissions, weight and economic revenue. The test case is the gas turbine-based power system serving an offshore platform in the North Sea.
Results indicate that the organic Rankine cycle technology presents larger performances compared to steam Rankine cycle units, whereas the implementation of air bottoming cycle modules is not attractive from an economic and environmental perspective compared to the other two technologies.
Despite the relatively high cost of the expander and of the primary heat exchanger, organic Rankine cycle turbogenerators appear thus to be the preferred solution to abate CO2 emissions and pollutants on oil and gas facilities.
As a practical consequence, this paper provides guidelines for the design of high-efficiency, cost-competitive and low-weight power systems for offshore installations.
Filamentous bacteriophages are widely used in phage display technology. The most common quantification method is lysis plaque formation test (PFT). This technique has several disadvantages, and only ...quantifies infective phages and is not effective when phagemids are used. We developed a qPCR method directed against the M13 replication origin, which detects between 3.3 × 10
3
and 3.3 × 10
8
viral genome copies with a linearity of
R
2
= 0.9998. Using this method we were able to observe a difference of approximately ten more phages than with the PFT. This difference was not due to the presence of a free genome, which suggests the presence of non-infective particles. Using a DNaseI treatment, we observed the presence of 30% to 40% of unpackaged genome in recombinant phage modified in PIII or PVIII. The qPCR method with a DNase I treatment is an efficient method to quantify the total amount of filamentous phages.
Purpose: Cone beam CT (CBCT) has been widely used for patient setup in image guided radiation therapy (IGRT). The radiation dose from CBCT scans is a clinical concern. The purpose of this study is to ...quantitatively evaluate CBCT dose to brain cancer patients under IGRT using a GPU‐based Monte Carlo CBCT dose calculation package gCTD. Methods: We first performed dose measurements in a water phantom scanned under Varian OBI system and the measurement data are used to commission gCTD. Eight brain cancer patients under IGRT are studied. For each patient, dose distribution under a standard head scan protocol is computed, in which a 100 kVp x‐ray source rotates around the patient head in a 200‐degree range through the posterior side. Mean dose to key organs are computed. Mean dose to 2% voxels that have the highest dose is also computed to characterize dose inhomogeneity. Results: For each CBCT scan, dose to brain, brainstem, chiasm, eyes, and optical nerves ranges in 0.24–0.28cGy, 0.22–0.31cGy, 0.13–0.17cGy, 0.036–0.13cGy, and 0.061–0.17cGy, respectively, depending on the patient head size and isocenter position. The dose is not homogeneous and the mean doses to 2% voxels with the highest dose for these organs are 0.40‐0.58cGy, 0.30–0.43cGy, 0.18–1.02cGy, 0.063– 0.28cGy, and 0.093–0.83cGy, respectively. Although mean dose inside body is 0.26–0.41cGy, the maximum dose can be up to 3.3 cGy, which locates on the bone. It takes about 1 minutes on an Nvidia C2050 GPU card to simulate 1 billion source photons, yielding an average relative uncertainty less than 1%. Conclusion: For the standard head scan protocol, while average CBCT dose to each organ is relatively low, the dose distribution is not homogeneous and the maximum dose can be substantially high. gCTD provides an efficiency and accurate way to evaluate CBCT dose in IGRT.
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