Engaging with farmers as entrepreneurs and partners: experiences with a self-assessment tool for farmer'organisations (FORCE)

Governments, donors and companies increasingly perceive small farmers and their organisations as development actors and business partners. A practical self-assessment tool, 'Farmers Organizations Reviewing Capacities and Entrepreneurship' (FORCE), takes up the challenge to translate the recognition of farmers' agency into operational practices. we demonstrate that FORCE is an effective tool to quickly map how farmers perceive their organisation and business relations. Self-assessment results of farmer groups in coastal Kenya illustrate how the tool is applied and how farmers' views are plotted in easily understandable scores and graphs

Development of Collembolans after coversion towards organic farming

In Northern Germany, a diverse and complex experimental farm of the Federal Agricultural Research Centre (FAL) was set-up in 2001 covering all main aspects of organic farming. Previously, the 600 ha farm had been managed conventionally. Adjacent conventional farms were used as reference. The aim of this project was to study collembolans, microbial biomass and soil organic carbon in six organically farmed fields managed as a crop rotation of six different crops compared with an adjacent conventionally managed field. We hypothesised that the specific management in organic farming promotes soil biota. Soil samples were taken during the growing season in 2004. Collembolan abundances and microbial biomass were lower under organic management, but, generally, collembolan diversity was higher in organically farmed fields combined with a shifting in the dominance structure of the species. This result reveals that, even after three years, the soil biota is still changing with management conversion

A new shielding effectiveness measurement method based on a skin-effect transmission line coupler

We propose a new convenient material shielding effectiveness measurement method based on a skin-effect transmission line coupler. The method is somewhat similar to the arrangement with two coupled TEM cells known from literature. The transmission line coupler consists of a pair of identical transmission line 2-port devices. Each device contains a coaxial waveguide, with a circular inner conductor and an outer conductor having a square cross section. One side of the outer conductor is left completely open as a slot. The slot is surrounded by a large metal housing to contact the two halves. As a measure for the shielding effectiveness the coupling between the two devices is measured in terms of scattering parameters after the test material is brought between the two halves. The devices can be used in a range from low frequencies to a few GHz

Algorithms for Skein Manipulation in a Genus-2 Handlebody

We present a series of algorithms for skein manipulation in a genus-2 handlebody, implementing a novel strand sorting method to reduce any skein to a skein in a 2-punctured disk. This reduction guarantees resolution as a linear combination of basis elements of the Kauffman Bracket Skein Module. Manually, these skein manipulations prove to be computationally intensive due to the inherent exponential nature of skein relations (i.e., a skein diagram with $n$ crossings yields $2^n$ new skein diagrams, each in $\mathbb{C}[t,t^{-1}]$, the Laurent polynomials with complex coefficients). Thus, as the number of crossings in a skein diagram increases, manual computations become intractable and automation desirable. We enable the automation of all skein computations in the genus-2 handlebody by first converting the skein diagram into an equivalent array, reducing the task of performing skein computations to that of implementing array operators, and then proving that we can always recover the resulting complex Laurent polynomial.Comment: Presented at the American Mathematical Society (AMS) Spring Southeastern Sectional Meeting, April 2023, Atlanta G

Nonlinear optical properties of a channel waveguide produced with crosslinkable ferroelectric liquid crystals

A binary mixture of ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The FLCs possess two important functionalities: a chromophore with a high hyperpolarizability $\beta$ and photoreactive groups. The smectic liquid crystal is aligned in layers parallel to the glass plates in a sandwich geometry. This alignment offers several advantages, such as that moderate electric fields are sufficient to achieve a high degree of polar order. The arrangement was then permanently fixed by photopolymerization which yielded a polar network possessing a high thermal and mechanical stability which did not show any sign of degradation within the monitored period of several months. The linear and nonlinear optical properties have been measured and all four independent components of the nonlinear susceptibility tensor $\bar d$ have been determined. The off-resonant $d$-coefficients are remarkably high and comparable to those of the best known inorganic materials. The alignment led to an inherent channel waveguide for p-polarized light without additional preparation steps. The photopolymerization did not induce scattering sites in the waveguide and the normalized losses were less than 2 dB/cm. The material offers a great potential for the design of nonlinear optical devices such as frequency doublers of low power laser diodes.Comment: LaTeX2e article, 15 pages, 10 figures, 11 EPS files, submitted to Physical Review

Measured Response of Local, Mid-range and Far-range Discontinuities of Large Metal Groundplanes using Time Domain Techniques

This work describes a method to detect and to quantify any local or mid-range discontinuity on extended flat metal planes. Often these planes are used for antenna calibration (open area test site-OATS) or the plane could be the ground of a semi-anechoic chamber used in Electromagnetic Compatibility (EMC) testing. The measurement uncertainty of antenna calibration or EMC testing depends on the groundplane's quality, which can be accessed using this method. A vector network analyzer with time-domain option is used to determine the complex-valued input scattering parameter S̄11,F of an aperture antenna in a monostatic setup. S̄11,F contains the information desired about the discontinuities and is measured in the frequency domain with high dynamic range. But only after a linear filtering utilizing the Chirp-Z-Transform the obtained time-domain signal S̄11,T give clear evidence of local and mid-range discontinuities