This master‘s thesis deals with cutting force analysis when tapping. This thesis includes basic methods of manufacture of threads, physical fundamentals of the cutting process, PVD coatings, tool materials, analysis and assessment of the testing nut taps with the application of PVD coatings.

The first part of work provides definition of basic parameters of threads, type of threads. Further work includes description of tools, material of tools and cutting forces. The final part of work deals with analysis course of cutting forces, analysis course wear and analysis surface structure of threads.

The diploma thesis deals with the monitoring of oxidative stability of products, oils and butter, from nut fruits. The theoretical part concentrates on the topic of nut fruits, their properties, compositions which are closely related to the effects on the human health and the possibilities of technological processing. The lipid storage process, especially the most frequently occurring autooxidation reactions are described, followed by experimental part of the thesis. The changes in coconut, walnut, peanut oils and peanut butter samples are monitored during storage at 4 ° C and 20 ° C by determining the acid value, the peroxide value and the fatty acid composition by the GC-FID method. The lowest oxidation stability showed walnut oil due to the highest content of unstable polyunsaturated fatty acids – up to 88,7 %. During storage at 20 ° C there was a statistically significant increase in the content of primary oxidation products, determined as peroxide value PV = 2,55 ± 0,12 µgROOHg-1. An increase was also observed in samples of peanut butter, but it was mainly due to higher water activity, which is important for chemical reactions. The durability of this product after opening mentioned on the product label correlates with their low stability

Plasma gasification experiments were conducted on sucrose and crushed macadamia nutshells. The pilot-scale plasma gasification system used comprises a 15 kW DC plasma torch fitted to a 5 L gasification reactor. The DC plasma torch has an efficiency of ~30 % with most of the energy lost in the torch anode. For the macadamia nutshells, the plasma input-power was set at 9, 11 and 14 kW. At each power input setting, four different feed rates were investigated, namely 0.5, 0.7, 1.04 and 1.14 kg/h. It was observed that as the power increases, conversion increases from 48 % at 9 kW to higher than 80 % at 14 kW. It was also observed that higher mass feed rates increase the conversion. The lower heating values of the syngas produced during gasification increased with higher power inputs and higher feed rates. At a feed rate of 1 kg/h, the maximum calorific power value was 3.45 kW, at a torch setting of 14 kW. The highest power values obtained was slightly more than 4 kW. The effect of equivalence ratio (ER) was evaluated on the plasma gasification of sucrose. ER values of 1 and 2 were investigated. With an ER of 1, the CO/H2 ratio was 1.8 and the CO/CO2 ratio was 109. With an ER of 2, the CO/H2 ratio was 1.73, and the CO/CO2 ratio 18. As expected, an increase in ER enhances the formation of CO2. A low ER thus results in higher syngas quality. At equivalent conditions the homogenous, crystalline sucrose yielded a CO/CO2 ratio of 109, significantly higher than the 29 for plasma gasification of the macadamia nut shells. A contributing factor to having better quality syngas, was the smaller the average particle diameter of the sucrose, 0.4 mm, compared to the 10 mm of the crushed macadamia nut shells was. Another contributing factor could be that the available carbon in the macadamia nut shells structure are more strongly bonded than in sucrose. For additional insight, kinetic data for the pyrolysis of sucrose, fructose and glucose were obtained using a TGA-FTIR hyphenated system, at much lower heating rates than anticipated in plasma system, and TGA-DTG experiments on macadamia nut shells. Dynamic studies were performed on sucrose, fructose and glucose at heating rates of 5, 10, 15, 20 and 50 °C/min in an atmosphere of nitrogen flowing at 50 mL/min, and for the macadamia shell at heating rates of 5, 10 and 20 °C/min in an atmosphere of nitrogen flowing at 50 mL/min. The sugars yielded 80 % to 85 % conversion into gaseous products, while the conversion of the shells approached 90 %; the residue was biochar. The FTIR spectra showed the major products that form from the pyrolysis of sugars to be CO2, H2O, along with large quantities C-H-O-containing compounds, amongst them C5H4O2 and C6H6O3. The latter two compounds are probably condensible. / Dissertation (MEng)--University of Pretoria, 2020. / Chemical Engineering / MEng / Unrestricted

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This master theses depicts FEM analysis of bolt joints where the focus is on investigating the stressrelationship between plate and bolt. Two bolts, M8 and M16, have been analyzed where they havebeen prestressed to 70 % of the ultimate tensile strength for steel type 8.8. A surface load has beenapplied in tension along the lateral surface of a cylindrical plate. The load distribution between plateand bolt of the external load varies between 2-28 % and 1-99 % for M8 and M16 in comparison to 20% stated in equation 2.7 in SS-EN 1993-1-8.The conclusion of studies shows that the behavior between the bolt and plate is not as previouslythought in SS-EN 1993-1-8. The bolt deforms negatively first when the system is subjected to externalload. This causes the resulting force to decrease. This behavior means that the bolt is designed towithstand larger loads than necessary. The factor 0.2 should be redefined. The authors recommendthat methods proposed by Pedersen and Pedersen [2008] or Haidar et al. [2011] should be used.

Despite the numerous environmental benefits of conservation buffers and incentives offered by cost-share programs, adoption remains low. Typical buffer designs often take arable land out of production. Multifunctional conservation buffers (MCBs) offer an alternative that supports rather than excludes production. By incorporating non-timber forest products (NTFPs), edible or ornamental crops can be harvested for profit or home use, while retaining key environmental services. Beyond low adoption rates, little is known about the long-term retention of conservation buffers due in part to limited program evaluation funding. However, implementation of evaluation recommendations is imperative for buffer retention. With this in mind, we administered a mail survey to conservation buffer adopters throughout Virginia. The first objective was to evaluate post-adoption experiences with conservation buffers. We identified four landowner clusters with distinct differences in buffer perceptions and intentions to retain. Insights can help conservation agencies enhance programming to reduce negative buffer experiences and increase long-term retention. The second objective was to determine interest in and preferences for MCBs. We found respondents were somewhat to very interested in MCBs, and increases in this interest were influenced most by the buffer's potential to decrease soil loss. Respondents who found MCBs more appealing than traditional designs had supportive peers and higher expectations of MCB performance. Lastly, respondents preferred MCBs designed with nut or fruit producing trees that grow naturally. Findings can help inform future outreach and programming aimed at merging conservation and production in buffer zones. / Master of Science

Riparian corridors are often farmed or grazed because they are typically productive and offer a low cost water supply for livestock. These areas are also critical in terms of water quality, soil retention, and aquatic and terrestrial wildlife habitat. Conservation of riparian areas can be conflicting due to loss of productive land for other uses. Agroforestry riparian buffers planted with native fruit and nut trees could help integrate conservation and production in this valuable space by giving landowners the opportunity to provide beneficial environmental services, while enhancing their opportunities for revenue. In order to realize potential use of this type of system, it is important to understand how to communicate benefits and improve prediction of adoption. With this in mind, we conducted a mail survey of creek side owners within three Virginia subwatersheds to 1) create typologies of underlying groups of landowners in order to develop relevant communication strategies for native fruit and nut tree ripairan buffers and 2) test the Unified Theory of Acceptance and Use of Technology (UTAUT) singularly and with additional agroforestry concepts to predict intention to adopt native fruit and nut tree ripairan buffers. Three landowner types were identified within the larger population of creek owners and exhibit differences that merit tailored communication strategies. Both models predict a noteworthy amount of intention to plant native fruit and nut tree riparian buffers. However, when agroforestry measures were added they explained a notable portion of variance. / Master of Science

Brazil nuts (Bertholletia excelsa, H.B.K.) are seeds of high nutritional value collected from South American rainforests and its productive chain is one of the most important non-timber economic activities in Brazilian amazon. The main objectives of this research were: 1) characterize the occurrence of chemical changes in Brazil nut kernels (BNK), cold-pressed Brazil nut oil (BNO) and Brazil nut flour obtained by water extraction (BNF); and 2) investigate strategies of control and monitoring these changes during storage. For this, consolidated techniques, such as spectrophotometry and chromatography, and a relatively new analytical technique, the electron spin resonance (ESR) spectroscopy, were employed. As major results, it was found that different combinations of storage temperatures and atmosphere packages have differently affected the tendency of radical formation and off-flavor volatile aroma compounds generation in BNK, and that the combination of refrigeration with vacuum packing was able to keep BNK at their best. It was demonstrated that a spin-trapping ESR spectroscopy method would be suitable to monitor oxidative changes in BNO with known history stored either in clear or in brown glass bottles under retail conditions. For BNF, it was demonstrated that minor variations on water activity (aw) might significantly affect the rates of both lipid oxidation and nonenzymatic browning reactions during storage. There was indication that for BNF with initial aw of 0.196, but not for BNF with initial aw of 0.101, under the studied conditions, secondary products from lipid oxidation might be substrates for nonenzymatic browning products formation. As a conclusion, these results may help to better understand chemical deteriorative processes in BNK and its co-products, according to the storage conditions, and that the use of less sample-demanding, fast and solvent-free analytical method to monitor these changes in BNO is feasible. / A castanha do Brasil (Bertholletia excelsa, H.B.K.) é uma semente de boa qualidade nutricional coletada em florestas tropicais da América do Sul, cuja cadeia produtiva é uma das mais importantes atividades econômicas não madeireiras da Amazônia brasileira. Os principais objetivos desta pesquisa foram: 1) caracterizar a ocorrência de alterações químicas em castanhas do Brasil (CB), óleo de castanha do Brasil obtido por prensagem a frio (OCB) e farinha de castanha do Brasil obtida por extração aquosa (FCB); e 2) investigar estratégias para controlar e monitorar essas alterações ao longo do armazenamento. Para isso, técnicas consolidadas como a espectrofotometria e a cromatografia, e uma técnica relativamente recente, a espectroscopia de ressonância de spin eletrônico (RSE), foram empregadas. Dentre os principais resultados obtidos, foi possível constatar o efeito de diferentes combinações de temperaturas e atmosferas de embalagem sobre a tendência de formação de radicais e sobre a geração de compostos voláteis de aroma relacionados a odor indesejável em CB, e que a temperatura de refrigeração combinada com a embalagem a vácuo foi a mais eficiente na preservação da qualidade da CB. Demonstrou-se que o uso de um método de aprisionamento de spins de RSE pode ser eficiente para monitorar alterações químicas em OCB com histórico conhecido embalado em frascos de vidro transparente ou marrons sob condições de armazenamento comercial. Para FCB, foi demonstrado que pequenas variações na atividade de água (aw) podem afetar significativamente as taxas de oxidação lipídica e de reações de escurecimento não enzimático durante armazenamento. Obteve-se indicação de que para FCB com aw inicial de 0,196, mas não para FCB com aw inicial de 0,101, produtos secundários da oxidação lipídica podem ser substratos para a formação de produtos do escurecimento não enzimático. Como conclusão geral, os resultados obtidos podem ajudar a explicar melhor os processos de deterioração química em CB e seus coprodutos, conforme as condições de armazenamento, e que o uso de um método que requer menor quantidade de amostras, é rápido e não usa solventes é viável para o monitoramento da qualidade de OCB.