The Varchenko Determinant of a Coxeter Arrangement

The Varchenko determinant is the determinant of a matrix defined from an arrangement of hyperplanes. Varchenko proved that this determinant has a beautiful factorization. It is, however, not possible to use this factorization to compute a Varchenko determinant from a certain level of complexity. Precisely at this point, we provide an explicit formula of this determinant for the hyperplane arrangements associated to the finite Coxeter groups. The intersections of hyperplanes with the chambers of such arrangements have nice properties which play a central role for the calculation of their relating determinants.Comment: 12 page

CloSpan Sequential Pattern Mining for Books Recommendation System in Petra Christian University Library

Petra Christian University (PCU) Library has been using website for their books search system. To further improve the service, it is necessary to develop the automatic system which can recommends the book or the correlation or the book which often being lend at the same time or sequentially by prospective borrowers. The algorithm used to explore the lending sequential patterns is CloSpan Sequential Mining algorithm. The output generated by this application is closed sequential pattern rules and the tree of sequential patterns. They can be used as a reference to establish a list of recommended related books. From the test results it can be concluded that the more data and smaller minimum support, the longer the process takes, and the more patterns that is produced. From the questionnaire outcome that are distributed to employees and users of the library can be concluded that the system can create right recommendations and useful

Kopy Luwak: a conservation strategy for global market

Subject area – Niche products and environmental ethics. Study level/applicability – The case is suitable for undergraduate students who have some understanding of competitive advantage in emerging economies, of niche products, the resource-based perspective and environmental ethics. Case overview – The case concerns the Indonesian coffee industry, specifically the production of Kopi Luwak, a coffee that involves a type of local wild animal as an essential part of the process. The case outlines a typical problem for a new leader who has to start his tenure with a creditable performance. The company is a resource-based one that has to manage a potential risk of violating environmental ethics. Expected learning outcomes – The case reveals the value of the international value chain for a cup of coffee. Through investigating the intersection between business feasibility and conservation issues, students should be able to understand what are appropriate business opportunities with environmental ethics considerations