Sun Data Research Articles

Pengaplikasian Astrolabe dalam Hisab Awal Waktu Shalat

Astrolabe is a classical instrument in astronomy that is often used to determine the position of celestial bodies without calculating. The notables who played role in the formulation of the astrolabe concept and work system were Hipparchus, Claudius Ptolemy and Theon. Muslim astronomers also had an important role in the development of the astrolabe. The application of astrolabe in reckoning the beginning of prayer time is very easy. But before it can be applied in reckoning prayer time, the astrolabe needs to be equipped with the Sun's altitude lines at the beginning of the prayer time for one year at a location. So the astrolabe can easily be applied to reckon the beginning of prayer times without the need to do calculations. But the Sun's data on the astrolabe are constant as well as the attitude of the Sun at the beginning of prayer time. Those are what reduce the accuracy of the beginning of prayer times reckoning result with the astrolabe.

Three‐Dimensional Reconstruction and Modeling of Middle Ear Biomechanics by High‐Resolution Computed Tomography and Finite Element Analysis

To present a systematic and practical approach that uses high-resolution computed tomography to derive models of the middle ear for finite element analysis. This prospective study included 31 subjects with normal hearing and no previous otologic disorders. Temporal bone images obtained from 15 right ears and 16 left ears were used for evaluation and reconstruction. High-resolution computed tomography of temporal bone was performed using simultaneous acquisition of 16 sections with a collimated slice thickness of 0.625 mm. All images were transferred to an Amira visualization system for three-dimensional reconstruction. The created three-dimensional model was translated into two commercial modeling packages, Patran and ANSYS, for finite element analysis. The characteristic dimensions of the model were measured and compared with previously published histologic section data. This result confirms that the geometric model created by the proposed method is accurate except that the tympanic membrane is thicker than when measured by the histologic section method. No obvious difference in the geometrical dimension between right and left ossicles was found (P > .05). The three-dimensional model created by finite element method and predicted umbo and stapes displacements are close to the bounds of the experimental curves of Nishihara's, Huber's, Gan's, and Sun's data across the frequency range of 100 to 8000 Hz. The model includes a description of the geometry of the middle ear components and dynamic equations of vibration. The proposed method is quick, practical, low-cost, and, most importantly, noninvasive as compared with histologic section methods.