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Agronomski in okoljski vidiki prekrivnih posevkov v ekološki pridelavi zelenjadnic
Martina Robačer, 2019, doktorsko delo/naloga

Opis: Cover crops can reduce the use of external inputs such as pesticides and fertilisers and can at the same time suppress weeds as well as improve or maintain soil fertility. Cover crops can also modify the microclimate which affects pest populations and diseases. Determining cover crop species and management practices is based on the needs and goals of production. The effects of introducing living mulch (LM) and management strategies on cash crop yield, product quality and energy use were studied in certain European countries (Slovenia, Italy, Germany and Denmark) in different climatic and soil conditions. In Slovenia, in organic production of cauliflower and leek, the effects of two terms of sowing white clover with additive design were compared with a production with black foil and with the usual agricultural practice by hoeing. In the field experiments the effect of LM on arthropod dynamics and activity density was investigated. The results demonstrated that the LM systems with a substitutive design, can be effectively implemented in vegetable production if the value of the ecological services (positive externalities) delivered by LM can counterbalance the yield loss due to the cash crop density reduction. If an additive design is used, the LM should be sown several weeks after the cash crop planting. Different cash crop genotypes (i.e., open pollinated/local cultivars in comparison with the hybrids) performed similarly. Use of human labor (HL) and fossil fuel (FF) energy slightly increased in LM systems (7%). The farmers’ acceptance of the LM techniques was quite high (75% of the interviewed sample). The LM technique did not affect the infestation of cabbage caterpillar Pieris spp., showing no detrimental effect of this technique on this key pest of cabbage. In Denmark, aphid populations were higher in the sole crop system than in the LM system. In Italy, a level of larval parasitization was detected and in the first year the percentage of parasitization was higher in LM (88%) than in sole crop (63%). Overall, the LM positively affected the activity density of Carabid beetles, also increasing the diversity and evenness of species (Slovenia and Italy) or activity density of some taxa (Slovenia and Denmark). Due to numerous agroecological services of cover crops, growing simultaneously with vegetables as LM, this could be promising technique for organic and others production systems in the future.
Ključne besede: organic vegetable production, cover crops, agroecological service, living mulch, energy consumption, biodiversity, soil arthropod
Objavljeno: 01.02.2019; Ogledov: 941; Prenosov: 126
.pdf Celotno besedilo (1,43 MB)

Yield performance and agronomic efficiency in oil pumpkins (Cucurbita pepo L. group Pepo) depending on production systems and varieties
Manfred Jakop, Silva Grobelnik Mlakar, Martina Bavec, Martina Robačer, Tjaša Vukmanič, Urška Lisec, Franc Bavec, 2017, izvirni znanstveni članek

Opis: In 2013 and 2014, a long-term trial (which was established in 2007) was conducted at the University Agricultural Centre in Pivola near Hoče. It included different production systems (conventional, integrated, organic, biodynamic), carried out in a field trial with oil pumpkins. The aim of the research was to analyse the effects of different production systems, varieties (hybrid and population variety) and years of production, on formation of oil pumpkin yields. The agricultural practice has been carried out in accordance with the applicable legislations and standards for the individual production system. When sowing, before fertilizing with nitrogen in early June and after the harvest, the amount of soil mineral nitrogen was monitored. We evaluated the number and weight of harvestable, unripe and decayed fruits, and yield of oil seed pumpkins and calculated the agronomic efficiency of the applied nutrients. The results showed that the year of production, the production system and the variety have a significant effect on some fruit characteristics and the yield of oil pumpkin seeds. The content of soil mineral nitrogen in May and September was significantly influenced by the production system and the year. In June, only the production system had a significant effect. The hybrid significantly increased the yields of oil pumpkin seeds in all production systems, even in the year that was less suitable for production. The agronomic efficiency of the applied nutrients in the biodynamic and organic production system is higher or equal than in the conventional production system, similarly, agronomic efficiency is higher in the hybrid compared to the oldest population variety efficiently. A comparable oil pumpkin yield can be expected in biodynamic and organic production, when proper nutrition and well carried out cultivation practices are combined with a new variety, when compared to less sustainable production systems, which often cause damage to the environment.
Ključne besede: production systems, variety, oil pumkins, mineral nitrogen, agronomic efficiency, yield
Objavljeno: 10.10.2018; Ogledov: 1053; Prenosov: 258
.pdf Celotno besedilo (290,91 KB)
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Damjan Maletič, 2015, doktorsko delo/naloga

Opis: Many organisations invest a considerable amount of capital and resources, implementing new techniques to improve their performance. An effective management of production and maintenance and processes is vital for economic viability and a long term survival of many industries. In fact, an effective and efficient maintenance process is essential to assure asset performance. With this recognition, the asset and maintenance management has become an indispensable element of strategic thinking of asset owners and asset managers. This research aims to investigate the interaction between quality management, production and maintenance performance. The relevant theoretical foundations and research gaps are presented first, followed by development of a conceptual framework. The framework builds upon resource-based theory (RBT) literature to develop a conceptual framework, mainly to understand how company’s resources could contribute to company’s performance. Based on this theoretical underpinning two main research streams are studied, namely quality management in maintenance and asset management. Different sources of data were utilized to answer the proposed research questions. The thesis includes two large-scale surveys (among Slovenian organizations as well as an international survey conducted in Slovenia, Sweden, Poland, Slovakia, Greece and Turkey) and two empirical case studies. The outcome of regression analysis provides the evidence that quality management orientation is an important predictor of maintenance performance. By testing the impact of quality management orientation on maintenance performance, this research shows that strong foundation on quality management orientation is an effective way of improving maintenance performance. Further, by examining continuous improvement in relation to maintenance performance, this research seeks to examine the role of quality management practices in achieving maintenance performance. In this regard it was found that continuous improvement significantly and positively affects the maintenance performance. In addition, results of this research revealed a mediator effect of continuous improvement on the relationship between quality management orientation and maintenance performance. Moreover, this research examines the relationship between physical asset management practices and sustainability and operational performance as well. The research is based on a premise that asset management, which comprises of risk management practices, performance assessment practices, life cycle management practices, policy & strategy practices, leads to improved organizational performance. The results of this research provide the evidence to support the hypotheses and to demonstrate that organizations can benefit from the implementation of asset management practices. The MANOVA furthermore provides interesting insights into the effects of asset management practices on the organizational performance. The results indicate that there are significant mean differences in organizational performance dimensions (as measured by the business performance, environmental performance, social performance and operational performance) for low and high levels of asset management practices. Therefore, by focusing on asset management practices, organizations can expect to achieve higher performance outcomes. In addition a comparison between Slovenian and Polish data subset was performed. The results revealed some distinct elements, namely regarding the performance outcome. For example, the results indicate that Slovenian organizations achieved higher scores in business, environmental and operational performance, while Polish organizations achieved higher scores in social performance.
Ključne besede: quality management, asset management, maintenance, production, performance
Objavljeno: 12.06.2018; Ogledov: 902; Prenosov: 86
.pdf Celotno besedilo (2,97 MB)

Material and energy balance in the planning of production costs
Manuela Ingaldi, Dorota Klimecka-Tatar, 2016, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Ključne besede: material, energy, manufacturing system model, production costs, planning
Objavljeno: 11.05.2018; Ogledov: 674; Prenosov: 66
.pdf Celotno besedilo (1,03 MB)
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3D-CO2-modelling for waste management in Styria/Austria
Wolfgang Fischer, Danko Simic, 2016, izvirni znanstveni članek

Opis: The paper in hand focuses on a calculation model which had been developed for calculating the CO2 production of a garbage truck during a waste collection tour. The challenge is the integration of not only the distance and loading weight but also the different petrol consumption and therefore CO2 production in regard to the topography of the whole collection tour. Additionally the increase of waste load at each stop during the whole collection tour has to be taken into account for the calculation. The model has been developed on basis of Excel. In order to get the real data from the collection tours these had been accompanied. There not only the whole tour but also all waste bins and stops for loading the waste had been registered. Both GPS (Global Positioning System) and RFID (Radio-Frequency Identification) had been used. The huge amount of data had to be scrubbed. This process of amending or removing data in a database that is incorrect, incomplete, improperly formatted, or duplicated was an important step to have reliable data for further calculation processes. The identification of the CO2 production during a waste collection tour including the topography and continuous revenue load had not been done so far and allows the identification of tour segments with lower but mainly higher or very high ecological impact. However, this is the basis for further discussions about options for optimizing the actual tours and habits of waste collection. That approach is part of a more comprehensive investigation of waste collection tours with general focus on economic, ecologic and social potentials for optimization.
Ključne besede: waste management, CO2 production of trucks, Styria, Austria
Objavljeno: 17.04.2018; Ogledov: 476; Prenosov: 60
.pdf Celotno besedilo (665,97 KB)
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Farms and mines: a conflicting or complimentary land use dilemma in western Australia?
Fiona Haslam McKenzie, 2009, pregledni znanstveni članek

Opis: The Western Australian economy has always been underpinned by farming and mining. Over the last five years the economy has experienced phenomenal growth due to unprecedented global demand for resources and increasingly, agricultural land is being given up for mining. Changing land uses challenge industry and community leaders; some communities are overwhelmed by a new population connected with mining, bringing with it a range of social and economic tensions that small communities struggle to cope with. This paper will discuss the conflicting issues regarding land use planning, local and environmental governance and sense of place while also canvassing positive developments that have enhanced community and regional economic development, thus building a resilient future.
Ključne besede: regional economic development, mining and energy sector, agricultural production, Australia
Objavljeno: 26.03.2018; Ogledov: 398; Prenosov: 68
.pdf Celotno besedilo (173,34 KB)
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Production control of a polymerization plant based on production performance indicators
Dejan Gradišar, Sebastjan Zorzut, Vladimir Jovan, 2008, izvirni znanstveni članek

Opis: The specifics of process manufacturing have a great influence on production management. The focus of process-production control is to maintain stable and cost-effective production within given constraints. The synthesis of production-control structures is thus recognized as one of the most important design problems in process-production management. This article proposes a closed-loop control structure with the utilization of production-performance indicators (pPIs) as a possible solution to this problem. Suggested concept takes into account also economic issues of production. pPIs represent the translation of operating objectives, such as the minimization of production costs, to a reduced set of control variables that can then be used in a feedback control. The idea of production-feedback control using production pPIs as controlled variables was implemented on a procedural model of a production process for a polymerization plant. Preliminary results demonstrate the usefulness of the proposed methodology. At the implementation stage we must be aware that appropriate IT system has to be available which ensures needed online production data.
Ključne besede: production management, production control, production performance indicators, model-based control
Objavljeno: 10.01.2018; Ogledov: 1394; Prenosov: 226
.pdf Celotno besedilo (963,78 KB)
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Lean manufacturing effects in a Serbian confectionery company
Ilija Djekic, Dragan Zivanovic, Sladjana Dragojlovic, Radoslava Dragovic, 2014, izvirni znanstveni članek

Opis: Background and Purpose: The objective of this paper was to evaluate effects of implementing lean manufacturing in a Serbian confectionery production company during a period of 24 months, emphasizing observed benefits and constrains. Company ‘case study’ is a leading confectionery producer in Serbia with annual production of more than 25,000 t. Methodology/Approach: The research method was case study. The approach in implementing lean manufacturing was structured in five phases, as follows: (i) training, (ii) analysis of lean wastes on one technological line, (iii) choice of lean tools to be implemented in the factory, (iv) implementation of lean tools in production and maintenance, (v) development of continual improvement sector and further deployment of lean tools. Results: Lean manufacturing tools implemented in the production process were visual control and single minute exchange of dies (SMED). Maintenance process implemented 5S with total productive maintenance (TPM) and problem solving sessions being the tools implemented in both processes. During the observed period, results of these tools showed the following: visual control tables initiated 61 improvement memos out of which 39% were fully implemented; a total of 2284 minor problems had been recorded, with over 95% of issues revealed in due time; total SMED time decreased for 7.6%; 19 problem solving sessions were initiated with 58% of solving effectiveness, and the remaining converted to on-going projects. In maintenance 5S improved from 29.9 to 60.3; overall equipment effectiveness (OEE) indicator increased from 87.9% to 92.3%; mean time between failure (MTBF) increased for 16.4%. Conclusion: As a result of all activities, 20 in-house trainings and 2 ‘kaizen’ events including motivational training have been initiated with 54 documents being revised and improved in order to contribute to more efficient processes.
Ključne besede: lean manufacturing, confectionery production, benefits, constraints
Objavljeno: 04.12.2017; Ogledov: 542; Prenosov: 90
.pdf Celotno besedilo (304,12 KB)
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A new somatic cell count index to more accurately predict milk yield losses
Janez Jeretina, Dejan Škorjanc, Drago Babnik, 2017, izvirni znanstveni članek

Opis: Intramammary infection and clinical mastitis in dairy cows leads to considerable economic losses for farmers. The somatic cell concentration in cow's milk has been shown to be an excellent indicator for the prevalence of subclinical mastitis. In this study, a new somatic cell count index (SCCI) was proposed for the accurate prediction of milk yield losses caused by elevated somatic cell count (SCC). In all, 97238 lactations (55207 Holstein cows) from 2328 herds were recorded between 2010 and 2014 under different scenarios (high and low levels of SCC, four lactation stages, different milk yield intensities, and parities (1, 2, and _>3). The standard shape of the curve for SCC was determined using completed standard lactations of healthy cows. The SCCI was defined as the sum of the differences between the measured interpolated values of the natural logarithm of SCC (ln(SCC)) and the values for the standard shape of the curve for SCC for a particular period, divided by the total area enclosed by the standard curve and upper limit of ln(SCC)=10 for SCC. The phenotypic potential of milk yield (305-day milk yield - MY305) was calculated using regression coefficients estimated from the linear regression model for parity and breeding values of cows for milk yield. The extent of daily milk yield loss caused by increased SCC was found to be mainly related to the early stage of lactation. Depending on the possible scenarios, the estimated milk yield loss from MY305 for primiparous cows was at least 0.8 to 0.9 kg day -1 and for multiparous cows it ranged from 1.3 to 4.3 kg day-1. Thus, the SCCI was a suitable indicator for estimating daily milk yield losses associated with increased SCC and might provide farmers reliable information to take appropriate measures for ensuring good health of cows and reducing milk yield losses at the herd level.
Ključne besede: dairy cows, milk production, lactation intervals, milk yield losses, somatic cell count index
Objavljeno: 24.10.2017; Ogledov: 820; Prenosov: 396
.pdf Celotno besedilo (317,33 KB)
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Multiple-effect evaporation in aluminosilicate technology
Dušan Klinar, Janvit Golob, 2001, strokovni članek

Opis: The article presents an engineering approach to the development of an alternative production with the existing equipment. Zeolite production is becoming an alternative to the old »Bayer« process for aluminum hydrate production. By applying appropriate know-how old equipment was used for an economically as well as ecologically acceptable production. In this equipment adaptation among other production steps the multistage evaporation battery was the most critical part of the process. We applied semi empirical approach on the basis of Z. Rant ideas to find heat transfer coefficients and to determine which equipment elements are more relevant for efficient performance and need serious maintenance.
Ključne besede: chemical engineering, evaporation in silicate technology, bauxite alumina production, evaporators, process optimization, heat transfer, heat flow, empirical equations, heat transfer coefficients, zeolites
Objavljeno: 24.08.2017; Ogledov: 642; Prenosov: 68
.pdf Celotno besedilo (354,14 KB)
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