ResumoOs depósitos aluvionares da bacia do Rio Jequitinhonha, em Minas Gerais, constituíram a fonte da maior parte dos diamantes produzidos no Brasil desde 1714 até meados da década de 1980. Essa importância histórica e econômica motivou a apresentação dos dados quanto à granulometria e qualificação gemológica dos diamantes nas áreas de concessão das mineradoras Tejucana e Rio Novo. Em adição, a amostragem adquirida em 14 pontos ao longo do rio é instrumental para a composição de um banco de dados, tendo em vista a identificação da origem de populações de diamantes. No mega-lote estudado, constituído por 186.052 pedras (17.689 ct), merece ser destacada a grande proporção (82,2%) de diamantes gemológicos.
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<div><p>Judo is a sport that is constantly evolving. Rule modifications and changes in tactical strategies have enhanced scoring opportunities and reduced penalties. This study analyzed the evolution of the temporal structure of combat through an assessment of the total match time (TMT), time engaged in combat (CT), time without (TWOG) and with grip (TWG), pause time (PT), the percentage of combat time in <em>tachi-waza</em> and combat in <em>ne-waza</em>, and the frequency of combat/tactical/technical actions/tasks. Data were descriptively analyzed overtime during the 2013, 2014, 2015, and 2017 World Championships and the 2016 Olympic Games. Data from 3,084 male and female matches across weight and gender categories were collapsed and used to compare the TMT, CT, TWOG, TWG, PT, and frequency of tactical actions over time and by competition phase (i.e., qualifiers, quarterfinals, recaps, semi-finals, bronze and finals). There were several temporal changes that occurred due to the rules modifications. The TMT increased by 3.6% over the sampling period for all competition phases. Regarding the duration of combat activities, relative to TMT: 25% was spent in PT (<em>M</em> PT = 8.9 s); 36% (<em>M</em> TWG = 9.6 s) was spent in TWG; 25% (<em>M</em> = 7.3 s) was spent in TWOG; 15% was spent in <em>ne-waza </em>(<em>M</em> = 7.7 s per action). With the changes of the rules in 2017, there was a Golden Point Score increase of 25% in the total number of combat; in relation to the competition phase, there was a 50% increase in the total number of combat activities. There was also a 15% increase in the number of actions in the competition final phase. There was some variation of the time structure of the combat, namely in the total time of the fighting and Golden Point, as a consequence of the change of the Referee rule changes.</p></div>
Cut diamonds are hard to value given the number and type of properties used in price construction. This project aims to develop a valuation model for cut diamonds based on data published on the Internet. Regression trees (Classification and Regression Trees and Chi‐Square Automatic Interaction Detection) and neural networks (using backpropagation) are used for this purpose. The proposed approaches have a complementary role in the application. Neural networks have a better performance in prediction, accounting for around 96% of cut diamond unit prices variation. The role of regression trees is fundamental in interpretability, helping to understand the contribution of predictors in pricing. The models' results may prove to have some advantages over the Rapaport price lists (an industry‐wide adopted price indicator).
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