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1.
JaTS, a Java 2D seismic tomography software, is presented. It implements original algorithms achieving optimal accuracy with reasonable computing costs. A second-order Fast Marching Method (FMM) is used for solving the eikonal equation, therefore enabling a fast and robust computation of seismic traveltimes between sources and receivers. The wavepaths are materialized by Fresnel volumes rather than by conventional rays. This approach accounts for complex velocity models and has the advantage of considering the effects of the wave frequency in the velocity model resolution. The model is computed by a Simultaneous Iterative Reconstruction Technique (SIRT) which has been reformulated to integrate Fresnel wavepaths by using a probabilistic approach. In addition, various utilities are implemented, such as a tapering filter, used to decrease artifact effects occurring in the vicinity of the sources and receivers. The software also offers the possibility of reconstructing the velocity field on a grid larger than the one used for the wave propagation computation. This contributes to stabilize the estimated values. All of the seismic processing tools have been integrated with a user-friendly graphical interface. JaTS represents a tightly integrated tool suite that supports the entire process of importing the SG2 field records, first-break picking, forward modeling and velocity-field computing across multiple platforms. 相似文献
2.
D. Lefkopoulos P. Grandjean A. Laouar M. Schlienger 《International journal of imaging systems and technology》1995,6(1):104-113
Dose distribution optimization algorithms are necessary in pencil-beam radiotherapy to exploit efficiently the multiple parameters of this powerful irradiation technique. We propose as an optimization technique singular value decomposition (SVD) analysis, which allows the measurement of ill conditioning of the stereotactic radiotherapy inverse problem and yields optimal weights for conformal treatment. Our approach to dose distribution optimization is to recover estimates of the minibeams weights from well-defined previsional dose matrices to study the influence of the different parameters on the stereotactic radiotherapy inverse procedure. The adjustment of the different parameters of the stereotactic irradiation to the “SVD optimizer” procedure is realized taking into account the ratio of the quality reconstruction to the calculation time. It will permit a more efficient use of the SVD optimizer in clinical applications with real three-dimensional lesions. We show the efficiency of the SVD optimizer in analyzing and predicting ill conditioning in stereotactic radiotherapy and in recognizing the topography of the different beams to create an optimal vector containing the beam weights (reconstructed weighting vector). 相似文献
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Etienne Grandjean 《Computational Complexity》1994,4(1):62-106
An operation on integers isLTTC if it is computable in linear time on a Turing machine (using the dyadic or binary representation of integers). AnLTTC-RAM (respectivelyI-RAM) is a RAM which only uses LTTC operations (respectively operations in the setI).The address-free time complexity measure of a RAM evaluates execution times using the logarithmic cost criterion but assumes that addressing operations are performed for free. 相似文献
5.
In a field study an adjustable VDT workstation was given to each of the 68 operators for one week. The preferred settings, the body postures and subjective evaluations were assessed during normal working activities of the operators. The preferred ranges disclose the following figures: keyboard height (home row above floor) 71-87 cm, screen height (centre above floor) 92-116 cm, viewing angles (eye to screen centre) + 2 to -26 degrees, visual distance (eye to screen) 61-93 cm. There was practically no correlation between preferred settings and anthropometric data of body length or eye levels above floor. The study of body postures revealed that the great majority of operators tend to lean backwards with trunk inclinations between 97 degrees and 121 degrees (95% confidence interval). Some of the preferred settings strongly differ from those recommended in many brochures and standards. The physical complaints in the neck-shoulder and back area are diminished with the preferred settings. 相似文献
6.
N. De la Cruz L. Esquius D. Grandjean A. Magnet A. Tungler L.F. de Alencastro C. Pulgarín 《Water research》2013
This study focuses on the removal of 22 selected micropollutants in an effluent from a municipal wastewater treatment plant (MWTP) at pilot scale. A reactor of 37 L with five low pressure mercury lamps emitting at 254 nm (UV254) was used. The 22 micropollutants include 15 pharmaceuticals, 2 X-Ray contrast medias, 1 corrosion inhibitor and 4 biocides/pesticides. Five of these 22 compounds were used as indicative substances as proposed by the Swiss Federal Office for the Environment (FOEN) (carbamazepine, diclofenac, sulfamethoxazole, benzotriazole and mecoprop). 相似文献
7.
Nyström B Becker-Van Slooten K Bérard A Grandjean D Druart JC Leboulanger C 《Water research》2002,36(8):2020-2028
Irgarol 1051 is a recent herbicidal compound, inhibitor of photosynthesis, used in antifouling paints. This toxic is persistent in aquatic environments, with low abiotic and biotic degradation, highly phytotoxic, and has already been detected in estuaries and coastal areas, with suspected negative impacts on non-target organisms (aquatic plants and algae). We measured the toxicity of Irgarol 1051 to macrophytes and phytoplankton from Lake Geneva (between Switzerland and France) by determining chlorophyll fluorescence yield, and phytoplankton primary production. Long-term toxicity for phytoplankton was estimated in a microcosm study, and growth inhibition tests were performed with isolated algal strains. The concentration of Irgarol 1051 was analysed in the water, and the most polluted site showed a higher level (up to 135 ng/L) than the lowest observed effect concentration for phytoplankton (8-80 ng/L), while the macrophytes appeared to be more tolerant to Irgarol 1051 in short-term tests. The microcosm study showed that phytoplankton structure might be even more sensitive to Irgarol 1051. 相似文献
8.
A semilongitudinal study was designed to follow-up the course of anxiety and depression in patients undergoing coronary artery bypass graft (CABG) surgery. The focus was on possible effects of gender and age on variations in both mean level and interindividual differences over time. At two timepoints before and two after surgery, 217 patients completed self-report questionnaires. Multivariate testing revealed an overall decrease in mean levels of anxiety and depression in the postoperative period but different trends for men and women. Compared with men, women reported more anxiety and depression, both pre- and postoperatively, but showed a relatively stronger decrease in the early postoperative period. Regarding variations in interindividual differences over time, multivariate testing revealed different trends of depression for men and women. Women appeared to be most homogeneous in the early days after surgery, whereas interindividual differences for men showed a stable trend. 相似文献
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10.
J de Mouzon J Mandry M Baron H Grandjean JM Rème M Monrozies G Pontonnier 《Canadian Metallurgical Quarterly》1982,11(2):201-213
The University Centre for Gynaecology and Obstetrics in Toulouse have been using a computerised record system for obstetrics since 1974. This makes it possible for a review for a review to be undertaken each year of the work carried out in the Service and has made it possible to study over six years the evolution of the characteristics of the population who have been followed, as well as the changes in attitudes and techniques adopted during pregnancy and labour. A study has been carried out on the factors associated with perinatal mortality and prematurity. Computerisation of 13,500 records has made it possible to draw curves of birth weights, according to the duration of the pregnancy, and characterising the service given. Finally the adoption of a prospective record system used in common by several teams and checked by people specialised in this work has improved the quality and quantity of retrieval and has made it possible to foresee cooperative studies between different departments. 相似文献