Precision Calibration of Radio Interferometers Using Redundant Baselines

Growing interest in 21 cm tomography has led to the design and construction of broadband radio interferometers with low noise, moderate angular resolution, high spectral resolution, and wide fields of view. With characteristics somewhat different from traditional radio instruments, these interferometers may require new calibration techniques in order to reach their design sensitivities. Self-calibration or redundant calibration techniques that allow an instrument to be calibrated off complicated sky emission structures are ideal. In particular, the large number of redundant baselines possessed by these new instruments makes redundant calibration an especially attractive option. In this paper, we explore the errors and biases in existing redundant calibration schemes through simulations, and show how statistical biases can be eliminated. We also develop a general calibration formalism that includes both redundant baseline methods and basic point source calibration methods as special cases, and show how slight deviations from perfect redundancy and coplanarity can be taken into account.Comment: 18 pages, 13 figures; Replaced to match accepted MNRAS versio

Refactoring Process Models in Large Process Repositories.

With the increasing adoption of process-aware information systems (PAIS), large process model repositories have emerged. Over time respective models have to be re-aligned to the real-world business processes through customization or adaptation. This bears the risk that model redundancies are introduced and complexity is increased. If no continuous investment is made in keeping models simple, changes are becoming increasingly costly and error-prone. Though refactoring techniques are widely used in software engineering to address related problems, this does not yet constitute state-of-the art in business process management. Process designers either have to refactor process models by hand or cannot apply respective techniques at all. This paper proposes a set of behaviour-preserving techniques for refactoring large process repositories. This enables process designers to eectively deal with model complexity by making process models better understandable and easier to maintain

Keeping the Cost of Process Change Low through Refactoring

With the increasing adoption of process-aware information systems (PAIS) large process model repositories have emerged. Over time respective models have to be re-aligned to the real world business processes through customization or adaptation. This bears the risk that model redundancies are introduced and complexity is increased. If no continuous investment is made in keeping models simple, changes are becoming increasingly costly and error-prone. Although refactoring techniques are widely used in software engineering to address related problems, this does not yet constitute state-of-the art in business process management. Consequently, process designers either have to refactor process models by hand or can not apply respective techniques at all. In this paper we propose a set of techniques for refactoring large process repositories, which are behaviour-preserving. The proposed refactorings enable process designers to effectively deal with model complexity by making process models easier to change, less error-prone and better understandable

SISTEM INFORMASI AKADEMIK BERBASIS WEB MENGGUNAKAN PENDEKATAN BERORIENTASI OBJEK PADA JURUSAN TEKNOLOGI INFORMASI POLITEKNIK NEGERI PADANG

Department of Information Technology Padang State Polytechnic growing rapidly, the number of students and the amount of data will increase too. However, these conditions will bring complex problems to the department to manage it in quantitative and qualitative way.  How complicated the problems faced when there are a lot of data that needs to be processed, and if it goes wrong it needs a long time to find, fix and change it. To minimize the errors and redundancies in processing the data, the department requires an academic information system. This system will manage student grades, final assignment and job training data at Information Technology Department. This web based Academic Information System was develop by using object oriented concept and JAVA especially J2EE technology as programming language and MYSQL Server as database. This system also design by using UML(Unified Modeling Language)