The effect of grasses grown for seed in mixture with legumes on the incidence of weeds and soil nitrogen content

This report was presented at the UK Organic Research 2002 Conference on behalf of the Colloquium of Organic Researchers (COR). The incidence of weeds and the content of soil nitrogen were investigated in the first year of a field trial with organic grass seed production in which the grasses were grown with companion legumes. Two grass species, timothy (Phleum pratense L.) cv. Sobol and perennial ryegrass (Lolium perenne L.) cv. Baca, were tested together with three legumes: red clover (Trifolium pratense L.) cv. Start, white clover (Trifolium repens L.) cv. Vysocan and black medick (Medicago lupulina L.) cv. Ekola. The N-nutrition and control of weeds were provided by three “ecological” methods and a conventional one (bacterial nodules of legumes, mulch, organic manure and mineral fertilizer). Plots with red clover had the lowest number of weeds, those with black medick the highest. Perennial ryegrass was more competitive than timothy against weeds and the companion legume. Soil nitrogen was highest in plots with white clover and red clover. During the vegetative period the level of soil nitrogen increased in the combinations with red clover, stayed the same in combinations with white clover, but decreased in those with black medick and in control plots

Planar Resonators for Metamaterials

This paper presents the results of an investigation into a combination of electric and magnetic planar resonators in order to design the building element of a volumetric metamaterial showing simultaneously negative electric and magnetic polarizabilities under irradiation by an electromagnetic wave. Two combinations of particular planar resonators are taken into consideration. These planar resonators are an electric dipole, a split ring resonator and a double H-shaped resonator. The response of the single resonant particle composed of a resonator with an electric response and a resonator with a magnetic response is strongly anisotropic. Proper spatial arrangement of these particles can make the response isotropic. This is obtained by proper placement of six planar resonators on the surface of a cube that now represents a metamaterial unit cell. The cells are distributed in space with 3D periodicity

Synthesis of Graphene on Metal/SiC Structure

The chapter deals with the synthesis of graphene on metal/SiC substrates. The graphene synthesis is pursued at a relatively low temperature. The method can be used for the graphene transfer from SiC to dielectric materials. Annealing of the structure results in a chemical reaction of a metal with SiC forming silicides and carbon-rich products at the boundary between metal and silicon carbide. Carbon atoms segregate at the top of metal/metal silicide layer during the cooling period of the process. The chapter is divided into the following sections: Introduction, Structure preparation, Graphene preparation from the structure Ni/SiC, Graphene preparation from the structure Co/SiC, Application of other metals, Influence of additive materials, and Conclusion

Universal Generator of Ultra-Wideband Pulses

An Ultra-Wideband (UWB) subnanosecond pulse generator is described in this paper. High amplitude Gaussian pulses are generated by a Step Recovery Diode (SRD) included in a novel pulse forming circuit. The pro-posed circuit solution utilizes the performance of the SRD effectively, without excessive requirements regarding the driver section of the generator. Monocycle pulses are then generated by an additional pulse forming network. A sim-ple transistor driver is also described, which transforms a TTL trigger signal to a driving pulse with the timing and amplitude parameters required by the SRD. Measurement results are presented, which show the proposed generator operating with stable output pulse parameters at arbitrary pulse repetition frequency up to 20 MHz. The generated monocycle pulses are 25 V in amplitude and approximately 500 ps in width

Ni and Ni Silicides Ohmic Contacts on N-type 6H-SiC with Medium and Low Doping Level

Ni silicides contacts, which are expected to be advantageous contact materials on SiC, were tested in this work. Prepared contact structures were ohmic with low contact resistivity approximately 8×10-4 Ω cm2 after annealing at 960°C as far as the SiC substrate with a medium doping level was concerned, no matter whether Ni or Ni silicides were used. At lower annealing temperatures, only Schottky behavior was observed by means of I-V characteristics measurements. In the case of SiC substrate with a low doping level, the behavior differed. It was necessary to anneal the structures at 1070°C to see ohmic behavior appearing with resistivities reaching 8×10-3 Ω cm2 and this was valid only for Ni and Ni2Si. Raman spectroscopy measurements confirmed formation of single Ni silicides as expected. It was found that Ni silicides can keep as good resistivity as Ni contacts while they interact with SiC in limited way and their undesirable drop-like morphology is expected to be overcome for example with a covering layer

Product Life Cycle Risk Management

Every new product coming to the market usually brings with a certain amount of doubt concerning the likelihood of its success. In particular, hidden problems and risks which might appear later in the product’s service life could cause producers’ difficulties, costing them a lot of money. This might even result in product phaseout and a consequent loss of the company’s reputation. Hence, it is necessary to manage all product risks. Unfortunately, no comprehensive methodology, managing the entire product life cycle, has been developed so far. This paper presents a new risk management methodology that covers the entire product life cycle. The product life cycle and its management have become a present standard and an important element of the information structure of modern enterprises. A product life cycle comprises several phases; this helps make risk management easier because it is feasible to manage risk for each phase separately. Generally, this phase structure creates a closed and unceasing rotation of risk management tasks and is an important element in universal process improvement. The methodology is focused on prioritizing risks according to the customer’s needs and requirements. It can be applied to a large number of different products and industries

ADSORBENTS FOR CO2 SEPARATION FROM FLUE GAS

The purpose of this paper is to determine the maximum adsorption capacity and the stability of impregnation agent ethanolamine to enhanced samples of activated carbon. Samples were characterized using BET surface analysis, BJH pore distribution and elemental analysis. Adsorption capacity was studied in a static regime in the pure CO2 atmosphere at the atmospheric pressure and at 30 °C and 50 °C. Stability of the impregnating agent bound to solid surface was studied by means of elemental analysis to specify the changes in nitrogen content before and after adsorption and before and after FID analysis. Flame-ionization detector was used to estimate the sum of organic compounds that were released from the solid surface at a given temperature. The results show that the best maximum adsorption capacity and impregnating agent stability among samples impregnated with MEA was for the molecular sieve 13X

New Planar and Volume Versions of a Metamaterial

Some characteristics of materials with negative permittivity and permeability, i.e., with a negative refrative index, known as metamaterials, are presented in this paper. Dispersion characteristics of left-handed parallel strips calculated by different methods are compared with each other. The calculated and measured dispersion and transmission characteristics of a newly proposed left-handed coplanar waveguide and of a novel volume metmaterial are shown. Simple equivalent circuits of both structures are presented together with elements values. The structures exhibit a negative refractive index in a wide frequency band