Nonsequential double ionization with few-cycle laser pulses

We investigate differential electron momentum distributions in nonsequential double ionization with linearly polarized, few-cycle pulses, using a classical model based on a laser-assisted inelastic (e(-),2e(-)) rescattering mechanism. These yields, as functions of the momentum components parallel to the laser polarization, are highly asymmetric and strongly influenced by the phase difference between the pulse envelope and its carrier oscillation, radically changing their sign around a critical phase. This behavior provides a powerful tool for absolute-phase measurements

Synopsis of marine prawn fishery of India for the third quarter of 1978

The data for the third quarter of 1978 is presented in this paper. The statewise and monthwise details of catch during the months of the quarter and the total catch of prawns for the quarter are summarized. Gearwise analysis of the catch, show that the prawn catch by shrimp trawlers increased from that of the previous quarter. In Kerala the trend of more prawn catch when the environmental features registered decrease in values noticed towards the end of last quarter continued in this quarter. In Kerala the trend of more prawn catch when the environmental features registered decrease in values noticed towards the end of last quarter continued in this quarter

Synopsis of marine prawn fishery of India for the second quarter of 1978

In continuation of the data on marine prawn fishery for the first quarter of 1978 presented in the September issue of the Marine Fisheries Information Service, Technical and Extension Series, the data for the second quarter of 1978 has been analysed

Synopsis of marine prawn fishery of India -1978

The details of the fishery for the last quarter of the year is dealt with first and then a general picture of the fishery for the whole year presented in this paper. The total catch figures for the previous quarters given earlier were provisional, whereas the final figures are used for the study of the fishery of the last quarter as well as the annual picture

Art and color in the context of CFD: Towards a better engineering design

Typically the words ‘art’ and ‘CFD’ tend to appear in the same sentence only as either ‘the art of using CFD’ or, particularly when conferences and meetings are announced, as ‘state-of- the-art’ CFD. Unquestionably in the latter context the art of good modeling is synonymous for representing reality as close as possible. Certainly this is true for both, numerical and experimental modeling. Color on the other hand is more fundamentally related with both, art and CFD. Indeed in the 1980s CFD was often nicknamed as ‘colored fluid dynamics’ as color was largely absent from experimental techniques at the time

High-order harmonic generation in a driven two-level atom: Periodic level crossings and three-step processes

We investigate high-order harmonic generation in closed systems using the two-level atom as a simplified model. By means of a windowed Fourier transform of the time-dependent dipole acceleration, we extract the main contributions to this process within a cycle of the driving field. We show that the patterns obtained can be understood by establishing a parallel between the two-level atom and the three-step model. In both models, high-order harmonic generation is a consequence of a three-step process, which involves either the continuum and the ground state, or the adiabatic states of the two-level Hamiltonian. The knowledge of this physical mechanism allows us to manipulate the adiabatic states, and consequently the harmonic spectra, by means of a bichromatic driving field. Furthermore, using scaling laws, we establish sharp criteria for the invariance of the physical quantities involved. Consequently, our results can be extended to a broader parameter range, as, for instance, those characteristic of solid-state systems in strong fields

The aerospace plane design challenge: Credible computational fluid dynamics results

Computational fluid dynamics (CFD) is necessary in the design processes of all current aerospace plane programs. Single-stage-to-orbit (STTO) aerospace planes with air-breathing supersonic combustion are going to be largely designed by means of CFD. The challenge of the aerospace plane design is to provide credible CFD results to work from, to assess the risk associated with the use of those results, and to certify CFD codes that produce credible results. To establish the credibility of CFD results used in design, the following topics are discussed: CFD validation vis-a-vis measurable fluid dynamics (MFD) validation; responsibility for credibility; credibility requirement; and a guide for establishing credibility. Quantification of CFD uncertainties helps to assess success risk and safety risks, and the development of CFD as a design tool requires code certification. This challenge is managed by designing the designers to use CFD effectively, by ensuring quality control, and by balancing the design process. For designing the designers, the following topics are discussed: how CFD design technology is developed; the reasons Japanese companies, by and large, produce goods of higher quality than the U.S. counterparts; teamwork as a new way of doing business; and how ideas, quality, and teaming can be brought together. Quality control for reducing the loss imparted to the society begins with the quality of the CFD results used in the design process, and balancing the design process means using a judicious balance of CFD and MFD

Feasibility study for estimating the offshore shear layer from on shore measurements

This paper presents an open source computational fluid dynamics (CFD) study of air flow over a complex terrain. The open source C++ toolbox OpenFOAM has been used for the CFD analysis and the terrain considered is a scale model of Berlengas Island, which lies close to the Portuguese coast. In order to validate the CFD model, experimental work has been carried out in an open-section wind tunnel using hot-wire anemometry to measure the wind profiles above the island. In the majority of cases, the OpenFOAM CFD solutions show very good agreement with the experimental wind profile data, confirming that open source CFD solutions are possible for environmental flows over complex terrain. Such an analysis demonstrates the feasibility of estimating offshore boundary layer effects from onshore measurements