Agriculture in Transformation: The Restructuring of Farm Enter in Central and Eastern European Countries during the Transition Process

Ten years of transition processes in the former communist countries of Central and Eastern Europe (CEEC) have changed the ownership structure as well as the structures and legal forms of enterprises in agriculture considerably. The farm structures in Eastern Europe developed under the influence of various collectivisation models. These influenced the course of the transformation process and therefore the development of new entrepreneurial and farm structures to a great extent. In addition also the effects of other political, social and economic factors with different weights can be noticed in the individual countries. Considering labour organisation and relation to markets, four different types of farm enterprises have evolved in the Central European and East European states during the transformation process: (a) Family farms for a mere self-sufficiency (Subsistence farms) (b) Family farms with a predominant orientation towards the market (c) Market-oriented joined family farms (d) Market-oriented farms with hired labour In the future farms and agricultural enterprises of all different types can have good prospects and therefore also the different sizes connected with them. For this reason the same should be valid for all types of farms and in the long term competition should decide, which types are going to compete. The preference or discrimination of a certain type by the agrarian policy needs to be avoided. The state also needs to develop the infrastructure in rural areas, to improve the prospects of farms that are deprived in this respect.Farm Management,

Paradoxical Magnetic Cooling in a Structural Transition Model

In contrast to the experimentally widely used isentropic demagnetization process for cooling to ultra-low temperatures we examine a particular classical model system that does not cool, but rather heats up with isentropic demagnetization. This system consists of several magnetite particles in a colloidal suspension, and shows the uncommon behavior of disordering structurally while ordering magnetically in an increasing magnetic field. For a six-particle system, we report an uncommon structural transition from a ring to a chain as a function of magnetic field and temperature.Comment: 3 pages, 2 figures. For recent information on physics of small systems see http://www.smallsystems.d

Bryophytes from the Cape Verde Islands

Almost 450 specimens of bryophytes, so far the largest collection of bryophytes ever made on the Cape Verde Islands, were collected in 1995 by the second author on the major islands of the archipelago. Twenty seven species (3 hepatics, 24 mosses) are reported as new to the Cape Verde Islands: Lejeunea ulicina (Tayl.) Gottsche et al., Riccia cavernosa Hoffm. emend. Raddi, Targionia hypophylla L., Barbula cf. consanguinea (Thwait. & Mitt.) Jaeg., Barbula unguiculata Hedw., Brachymenium exile (Dozy & Molk.) Bosch. & Lac., Bryoerythrophyllum ferruginascens (Stirt.) Giac., Bryoerythrophyllum inaequalifolium (Tayl.) Zander, Bryum cellulare Hook., Chenia leptophylla (C. Müll.) Zander, Desmatodon bogosicus C. Müll., Didymodon australasiae (Hook. & Grev.) Zander, Didymodon maschalogena (Ren. & Card.) Broth. (Didymodon michiganensis [Steere] K. Saito), Didymodon vinealis (Brid.) Zander var. flaccidus (B.S.G.) Zander, Eurhynchium meridionale (B.S.G.) De Not., Eurhynchium speciosum (Brid.) Jur., Fissidens sciophyllus Mitt., F. bogosicus C. Müll., F. flaccidus Mitt., F. helictocaulos C. Müll., Gymnostomiella cf. vernicosa (Hook.) Fleisch., Gymnostomum calcareum Nees & Hornsch., Hyophila involuta (Hook.) Jaeg., Orthotrichum diaphanum Brid., Tortula cuneifolia (With.) Turn., Tortula laevipila (Brid.) Schwaegr. and Weissia microstoma (Hedw.) C. Müll. The doubtful record of Marchantia paleacea Bertol. could be confirmed. Numerous species are recorded as new to single islands. Tortula pierrotii Biz. described from Tanzania has proved to be synyomous with Bryoerythrophyllum inaequalifolium. Didymodon maschalogena (Ren. & Card.) Broth. is an older name for Didymodon michiganensis (Steere) K. Saito. A study of types of species described as endemic to the Cape Verde Islands revealed that Barbula bolleana (C. Müll.) Broth. is an earlier name for Hydrogonium bolleanum (C. Müll.) Jaeg., Barbula elliottii Broth., Barbula kivuensis Leroy & P. de la Varde and Barbula madagassa Ren. & Card. are synonymous with the latter, Hyophila crenulata C. Müll. ex Dus. var. brevifolia Bizot is synonymous with Hyophila involuta (Hook.), Barbula sulcata Geh. is synonymous with B. convoluta Hedw. and Tortula subcaroliniana Bizot is synonymous with Tortula amphidiacea (C. Müll.) Broth. In addition to the so far unpublished results of recent collections, a complete survey of the bryophyte flora of the Cape Verde Islands is given. A hundred and sixty two species (2 species of hornworts, 36 species of hepatics and 124 species of mosses) are so far known from this archipelago

Scientific results of the Bryotrop expedition to Zaire and Rwanda : 3., photosynthetic gas exchange of bryophytes from different forest types in eastern Central Africa.

During the BRYOTROP-Expedition to Zaire and Rwanda bryophytes were collected from a rainforest habitat at 800 m a.s.l. and from bamboo forest and tree-heath environments between 2200 and 3200 m. The microclimates influencing the mosses are different at the altitudinally separated locations. Conditions are rather constant with 24 °C, 100 % rel. hum. and PAR below 100 μmol photons m-2 sec-1 at the lowland station, rather versatile in the mountains with six times higher daily sums of PAR, temperatures between 10 and 25 °C and relative humidities between 60 and 1oo %. In the bamboo forest epiphytic mosses dry out during the day to less than 70 % of their water content, but regain saturation from the vapor-saturated air during night. Bryophyte photosynthesis and respiration were studied by Warburg manometry with moisture saturated samples. Temperature curves of gas exchange peaked between 22 and 30 °C. Optima of the lowland species were somewhat higher than those from samples collected at the mountain sites. Habitat separation of characteristics of photosynthesis was more pronounced with respect to light responses. Saturation gas exchange rates were reached by all species still below 400 μmol photons m-2 sec-1. But the slopes of the curves in the low-light range were distinctly steeper, and the light compensation points smaller in the lowland than in the highland species (compensation points of the former: 3 - 12 μmol photons m-2 sec-1, of the latter: 8 - 20 μmol photons m-2 sec-1). It is emphasized that bryophytes in the rainforest understory experience extremely high ambient C02 concentrations near the floor. This, their low light requirements for photosynthesis, and the permanently optimal temperature and humidity conditions for maximal carbon gain enable them to live successfully, but with less biomass development in this dark and damp environment. By contrast, bryophytes from the bamboo forest and tree-heath environments can utilize light conditions combined with variable temperatures and humidities similarly as species from extratropical vegetation types

Modelling a partially liquid-filled particle damper using coupled lagrangian methods

Energy dissipation in particle dampers (PDs) is complex and occurs mainly due to the relative motion between particles and to their surroundings. The degree of relative motion is particularly sensitive to changes in the external vibration amplitudes. Low vibration amplitudes lower the relative motion between solid particles, and thus lead to significantly lower energy dissipation rates. In order to influence the degree of relative motion between solid particles, a method is investigated in which the PD is filled with a combination of solid and liquid fillings. Moreover, with the PD partially filled with a liquid, the solid particle shape plays a more profound role in enhancing the damping performance. In order to investigate the effects of complex particle shapes and an added liquid, a simulation model based on Lagrangian methods is presented in this work. In order to validate the simulation models, experiments were also carried out. The experimental setup consists of a PD mounted on a vertical leaf spring. The PD is a cylindrical container filled with complex shaped particles in combination with a liquid. The complex shapes, here chosen to be tetrapods, were manufactured using a Stereolithography 3D printer. A good agreement between simulations and experiments is observed. In order to gain a deeper insight, a numerical study is pr sented which investigates the effects of solid-liquid ratio on the dissipated kinetic energy

Two-phase modeling of conduction mode laser welding using smoothed particle hydrodynamics

The process of conduction mode laser welding is simulated using the meshless Lagrangian method Smoothed Particle Hydrodynamics. The modeling of the solid phase is based on the governing equations in thermoelasticity. For the liquid phase, surface tension effects including the Marangoni force caused by a temperature-dependent surface tension gradient are taken into account to simulate the melt flow in the weld pool. A non-isothermal solid-liquid phase transition with the release or absorption of additional energy known as the latent heat of fusion is considered. The major heat transfer process through conduction is modeled, whereas heat convection and radiation are neglected. The energy input from the laser beam is approximated as a Gaussian heat source acting on the material surface. Numerical results obtained with the developed model are presented for laser spot welding and seam welding of aluminum. The change of process parameters like welding speed and laser power, and their effects on the weld pool dimensions can be investigated through simulations, and the overall welding quality may be assessed

Comparison of wear models using a lagrangian approach

Abrasive wear of hydraulic machines is commonly simulated with grid based methods. In this work we present a mesh-free approach for modeling abrasive wear. The transport fluid is modeled with the Smoothed Particle Hydrodynamics method. The ad- vantage of this method is the simple handling of free surfaces and complex interfaces, e.g., the interface between the fluid and the abrasive particles. The small solid particles and the boundary geometry of the machine are simulated with the Discrete Element Method. The amount of removed material on the boundary geometry is predicted with three wear models with different complexity. We simulate the impact of a free jet with particle load- ing on a simplified pelton bucket as working example. The resulting wear patterns of the three different wear models are analyzed and compared. In this work we take the parameters for the wear models from literature