1,720,982 research outputs found
Modeling of capillary wick irrigation system for potted plant and small scale plantation
Full text linkLimited availability of fresh water supplies worldwide demonstrates the urgent need to develop and adopt efficient irrigation methods and proper irrigation management strategies. The relatively high performance of drip irrigation is no doubt. It saves a substantial amount of water and labor, increases yields, and often also improves the quality of the produce. However, the higher investment and energy cost limit the development of the low-cost irrigation system for subsistence farmers. There has been an immense interest in developing and promoting the low-cost drip irrigation system appropriate for small-scale crop growers and greenhouse crop production. This study, by conducting laboratory experiments,investigated hydraulic characteristics and performance of cotton-bonded non-woven material to be used as the wick emitter. Furthermore, greenhouse experiments were carried out to simulate water movement and solute dynamics under root water uptake for potted eggplant crops. To determine proper water application strategies, three irrigation schedules were evaluated. The wick emitter provided the uniformity coefficient of 95.65% and distribution uniformity of 92.67% in applying irrigation in two growing media: peatgro (peat), coconut coir dust and sandy clay loam soil. The growing media and the soil were wetted in an axially symmetric pattern under the wick emitter; in traditional and modern watering methods,growing media are wetted in one-dimensional pattern. HYDRUS simulation of water distribution revealed the dependency of the spatial extent of the wetted zone in the growing media on water application period and hydraulic properties of the media. Furthermore, the results demonstrated that the solutes are transported very slowly, and most of the nutrient solution remains within the middle and bottom of the pots. The results from this study revealed that the eggplant growth showed insignificant differences for the three irrigation schedules when fresh water was used because all the three irrigation schedules provided with enough water content for the crop. In contrast, the eggplant growth showed differences between the treatments relatively when nutrient solutions were used. In terms of wick water application strategies, although 202 ml/day of nutrient solution was applied for the Management Allowed Deficit (MAD) treatment and 155 ml/day was applied for Evapotranspiration (ET) treatment. The total leaf area of the ET schedule (1252.9 cm2) was higher than the total leaf area of the MAD (1007.8 cm2). The result suggests that the ET schedule is the best under wick irrigation. Discharge of the wick emitter followed an inverse linear relation with a capillary height of water in the wick. This relation led to the development of an equation for compensating wick emitter discharge by replacing the pressure head of a drip emitter with capillary height of the wick emitter. The measured water volume found the close match with the simulated water and solute movement using HYDRUS 2D/3D in a container planted with brinjal plant and for various porous mediums. The findings from this study invoke opportunities to develop an effective Capillary Wick Irrigation System (CWS) for small-scale crop production. Further investigation would provide generalized broader evidence on CWS performance based on techno-economical performance of the wick under diverse conditions
Hydraulic characteristics of capillary wick irrigation system
No full textLimited availability of freshwater supply worldwide demonstrates urgent need to develop and adopt efficient irrigation methods and effective irrigation management strategies. This study, by conducting laboratory experiments, investigated hydraulic characteristics and performance of cotton-bonded non-woven material to be used as wick emitter. The wick emitter provided uniformity coefficient of 95.65% and distribution uniformity of 92.67% in applying irrigation in two growing media - peatgro (peat) and coconut coir dust. The growing media were wetted in an axially symmetric pattern under the wick emitter; in traditional and modern watering methods, growing media are wetted in one-dimensional pattern. HYDRUS simulation of water distribution revealed dependency of spatial extent of the wetted zone in the growing media on water application period and hydraulic properties of the media. Discharge of the wick emitter followed an inverse linear relation with capillary height of water in the wick. This relation lead to development of an equation for compensating wick emitter discharge by replacing pressure head of drip emitter with capillary height in wick emitter. The findings of this study thus invoke opportunities to develop an effective Capillary Wick Irrigation System (CWS). Further investigation would provide a generalized broader evidence on CWS performance based on techno-economical performance of the wick under diverse conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Impact of thermo-hydrolytically treated wood fibers as a substrate component on the growth of petunias (Abstract)
No full textImpact of thermo-hydrolytically treated wood fibers as a substrate component on the growth of petunias
No full textWood fibers can contribute to replacing peat in growing media and thus help to protect peatlands. As domestic, renewable raw materials, they represent a sustainable option for this purpose. To date, however, wood fibers are usually used as a peat substitute at a maxi-mum of 30% (v/v). A main reason for this limitation is the insufficient microbial stability of wood fibers, which favors nitrogen immobilization and can thus impair nitrogen supply of plants. To address this drawback, in this study wood fibers were subjected to different thermal or thermal-hydrolytic treatments. Seedling tests with napa cabbage were conducted to determine whether treated wood fibers were free of phytotoxic substances. Mixtures with 50% (v/v) wood fiber and white peat each were used. In addition, three wood fiber varieties were evaluated in the cultivation of petunia. Two wood fiber proportions (30 and 60% v/v) and two nitrogen fertilization rates (common and increased supply) were included in each case. In the seedling trial with napa cabbage, no phytotoxic effects were detectable in any of the wood fiber variants investigated. However, when cultivating petunias, both shoot mass growth and number of flowers decreased with increasing wood fiber content. In substrates with a wood fiber content of 60% (v/v), plant development was inhibited so severely that the petunias no longer achieved marketable quality. Increased nitrogen fertilization was able to compensate for this negative effect only in few cases. This suggests that other factors than nitrogen limited plant growth in wood fiber-rich substrates. Among others, physical proper-ties such as the lower water capacity of wood fibers may be a cause. More in-depth investigations are still required in this regard
Aus dem Brutschrank ins Gewächshaus – Bewertung des Stickstoffhaushalts in Substraten (Abstract)
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