Flora – Vegetatie voor een betere luchtkwaliteit; Meten is weten, Vegetatie voor een betere luchtkwaliteit

In dit ontwikkeldocument wordt een beschrijving gegeven van een meetproef langs de A50 bij Heteren waar de effecten van een beplantingsstructuur op de luchtkwaliteit worden gemeten. Hierin worden de inrichting van het proefvak, de mogelijk optredende risico’s, het uitvoeren van de metingen en de beschrijving van de modelering beschreven

Gain without population inversion in V-type systems driven by a frequency-modulated field

We obtain gain of the probe field at multiple frequencies in a closed three-level V-type system using frequency modulated pump field. There is no associated population inversion among the atomic states of the probe transition. We describe both the steady-state and transient dynamics of this system. Under suitable conditions, the system exhibits large gain simultaneously at series of frequencies far removed from resonance. Moreover, the system can be tailored to exhibit multiple frequency regimes where the probe experiences anomalous dispersion accompanied by negligible gain-absorption over a large bandwidth, a desirable feature for obtaining superluminal propagation of pulses with negligible distortion.Comment: 10 pages + 8 figures; To appear in Physical Review

Quantum trajectory simulations of the fluorescence intensity from a two-level atom driven by a multichromatic field

The quantum trajectories method is illustrated for the resonance fluorescence of a two-level atom driven by a multichromatic field. We discuss the method for the time evolution of the fluorescence intensity in the presence of bichromatic and trichromatic driving fields. We consider the special case wherein one multichromatic field component is strong and resonant with the atomic transition whereas the other components are much weaker and arbitrarily detuned from the atomic resonance. We find that the phase-dependent modulations of the Rabi oscillations, recently observed experimentally [Q. Wu, D. J. Gauthier, and T. W. Mossberg, Phys. Rev. A 49, R1519 (1994)] for the special case when the weaker component of a bichromatic driving field is detuned from the atomic resonance by the strong-field Rabi frequency, appear also for detunings close to the subharmonics of the Rabi frequency. Furthermore, we show that for the atom initially prepared in one of the dressed states of the strong field component the modulations are not sensitive to the phase. We extend the calculations to the case of a trichromatic driving field and find that apart from the modulations of the amplitude there is a modulation of the frequency of the Rabi oscillations. Moreover, the time evolution of the fluorescence intensity depends on the phase regardless of the initial conditions and a phase-dependent suppression of the Rabi oscillations can be observed when the sideband fields are tuned to the subharmonics of the strong-field Rabi frequency. [S1050-2947(98)03501-X]

Resonance fluorescence and Autler-Townes spectra of a two-level atom driven by two fields of equal frequencies

We study the effects of driving a two-level atom by two intense field modes that have equal frequencies but are otherwise distinguishable; the intensity of one mode is also assumed to be greater than that of the other. We calculate first the dressed states of the system, and then its resonance fluorescence and Autler-Townes absorption spectra. We find that the energy spectrum of the doubly dressed atom consists of a ladder of doublet continua. These continua manifest themselves in the fluorescence spectrum, where they produce continua at the positions of the Mellow sideband frequencies omega(L)+/-2 Omega of the strong field, and in the Autler-Townes absorption spectrum, which becomes a two-continuum doublet

Fluorescence spectrum of a two-level atom driven by a multiple modulated field

We investigate the fluorescence spectrum of a two-level atom driven by a multiple amplitude-modulated field. The driving held is modeled as a polychromatic field composed of a strong central (resonant) component and a large number of symmetrically detuned sideband fields displaced from the central component by integer multiples of a constant detuning. Spectra obtained here differ qualitatively from those observed for a single pair of modulating fields [B. Blind, P.R. Fontana, and P. Thomann, J. Phys. B 13, 2717 (1980)]. In the case of a small number of the modulating fields, a multipeaked spectrum is obtained with the spectral features located at fixed frequencies that are independent of the number of modulating fields and their Rabi frequencies. As the number of the modulating fields increases, the spectrum ultimately evolves to the well-known Mellow triplet with the sidebands shifted from the central component by an effective Rabi frequency whose magnitude depends on the initial relative phases of the components of the driving held. For equal relative phases, the effective Rabi frequency of the driving field can be reduced to zero resulting in the disappearance of fluorescence spectrum, i.e., the atom can stop interacting with the field. When the central component and the modulating fields are 180 degrees out of phase, the spectrum retains its triplet structure with the sidebands located at frequencies equal to the sum of the Rabi frequencies of the component of the driving field. Moreover, we shaw that the frequency of spontaneous emission can be controlled and switched from one frequency to another when the Rabi frequency or initial phase of the modulating fields are varied

De integrale beplantingsmethode, naar een dynamische benadering voor het ontwerpen van beplantingen

Public parks and gardens (planting structures) in urban areas are subject to various forms of human intervention, based on traditional planting methods. These forms of intervention are related to the creation of individual space required for mature growth of ligneous plants by thinning or by limiting growth in cases where plants exceed the space delineated for them. Such intervention is costly, must be executed timely in order to prevent irreversible deformity, and influences undamaged growth.The objective of this study is to resolve the contradiction between human intervention and undamaged growth by adopting a planting method which is based on a dynamic approach to the design of planting schemes. This dynamic approach has led to the integral planting method as a theoretical model; in this method, the space required for maximum growth in a plant's mature phase is combined with the realisation of architectural functions. The desired effect is defined by the initial size of the trees and shrubs. The growth movement towards the dimensions of the maturity phase is part of a composition in time and space in accordance with a so-called 'planting-film'. Because the growth rate of the plants defines the above-mentioned composition, human intervention can be reduced to a minimum. In addition, the integral planting method contains a set of instruments to define the space for growth to a certain size at a certain point in time in location-specific circumstances. By providing sufficient room for growth and by relating life span to environment dynamics, unexpected changes in future growth development can, to a certain extent, be compensated.The retrospective in Chapter 2 shows that with the planting method applied in the three cases (Haarzuilens, Amsterdamse Bos, Bijlmermeer Groenstructuur), people are always aiming for quick results and planning for future growth requires much effort, which must be enforced timely and systematically to ensure that the desired effect is not affected irreversibly (Bijlmermeer Park Structure) or operational backlog is not increased further.It is essential that the terminology used is unambiguous to define and legitimize the objective or intended development of a planting structure during the analysis phase. To achieve this unambiguousness, Chapter 3 provides a description of the morphology and morphodynamics (dimensions, growth rate, life span) of the elements used to describe the defined situation. This description, as defined in the tables 'Classification of free-standing forms', Planting typology I, II, III and IV, has led to unambiguous terms and definitions. This will lead to the motivation for the planting scheme (initial situation: initial dimensions, planting distances, assortment) and the planting film (the defined situation). Next, the 'growth', as the effect of movement, is derived from the growth curve survey for each element. The growth curve survey reproduces the morphodynamic aspects in a simplified linear growth curve. The transformations of planting types are shown tobe brought about on the basis of morphodynamics. The Cd-rom supplied with this thesis shows these dynamics from different angles, in the form of a planting film.Chapter 4 describes the principles of the adopted, not-adopted, identical and shifted position, with which the morphodynamic aspects of the plant can be applied strategically to also realise transformations of the plant types. The implementation of the growth curve survey shows how larger plant material can be used to start with. The example of a 2-acre park in Boxmeer shows what the principles for freestanding plant shapes bring about in real situations. The operating method and manual clarify how a starting situation (the planting scheme) and its related management regime (execution and maintenance plan) can be derived from the defined situation to which it should lead.In chapter 5 a comparison is made to ascertain how the integral planting method behaves in relation to the traditional method. When designing parks and gardens, the definition of assortment, planting interval, initial size and construction and maintenance method covers many variables such as architecture, micro climate, soil, opinions on contruction and maintenance method, quality of base materials, organisation of implementation and so on.These aspects are covered in anumber of cases (Polderpark Almere, Bakenhof Arnhem, Prins Bernhardbos Hoofddorp).The method applied in the comparison covers four steps. Step one describes the defined situation and the set-up according to the original planting method. Step two covers the growth curve survey which defines the location-specific morphodynamic characteristics of the plants involved for their actual as well as projected or future growth. Step three contains a fully worked-out planting and maintenance plan based on the alternative planting method and starting from the same defined situation as in step one.In step four the architectural and cost aspects of both planting methods are compared. The architectural aspects show the morphodynamics of the plant structure in the long term with the aid of views and diagrams drawn to scale, elucidated with data from the location-specific growth curve survey and field observations of the actual situation. The cost aspects are based on construction and maintenance for the first 30 years, expressed in cumulative, indexed and hard cash amounts, shown graphically for each planting method in the different cases.The results of the comparison show that a screen or block based on the traditional planting method will reach full functionality at eye level after 4 - 7 years. With the integral planting method, the results of a screen or block will be visible at eye level from the start, and full functionality will be reached after 8 - 13 years. With the traditional method, it appears to be almost impossible to realise free-standing forms, in practice as well as in simulation during the growth curve survey. Empirical research of the Prince Bernhard forest, which was developed according to the integral planting method, shows that the head start of the larger initial sizes of the free-standing forms in this method provides the visitor with an increased sense of security because of the openness of the plant structure and the fact that this method leads to a completed planting structure in a shorter period of time.In addition, the comparison shows that the construction costs using the integral planting method are about double the costs using the traditional planting method. However, the maintenance costs for free-standing forms when the integral planting method has been applied are so low, that cost recovery will occur within a foreseeable period, as compared with the traditional planting method (urban variant).The integral planting method can be applied to small- and large-scale urban and small-scale rural park projects. For large-scale rural projects application of the integral planting method requires further investigation of the relation between architectural functions of planting structures and forest ecology and forest management.Tree nurseries will need to put more effort into the methods for breeding and planting larger plant material. Some growers already guarantee that their plants will start growing immediately after planting and they offer care and maintenance of these larger inital sizes of trees and shrubs for a maintenance period of 10 years and longer