This paper discusses on uncertainty and optimal sensor placement for estimating multi-phase flow rates from the producing well by inversely solving the well flow model, given the down-hole temperature and pressure measurements. Uncertainty of the estimated multi-phase flow rates are evaluated by solving the error propagation from the given uncertainties of pressure and temperature measurements used to make the estimation. The uncertainties of the multi-phase flow rate estimations are studied for different sensor combination and location to search for the optimal sensor placement which gives the lowest uncertainty for multi-phase flow rate estimations. From the simulation study, preferred sensor combination and location of pressure and temperature measurements are found for typical oil gas 2-phase vertical well case. The methodology can be applied for reliable down-hole multi-phase flow monitoring and optimal sensor placement design for monitoring the multiphase flow rate using temperature and pressure measurements within an allowable estimation uncertainty and sensor cost.
This study aimed to establish and verify the validity of an acoustic simulation method during sustained phonation of the Japanese vowels /i/ and /u/. The study participants were six healthy adults. First, vocal tract models were constructed based on computed tomography (CT) data, such as the range from the frontal sinus to the glottis, during sustained phonation of /i/ and /u/. To imitate the trachea, after being virtually extended by 12 cm, cylindrical shapes were then added to the vocal tract models between the tracheal bifurcation and the lower part of the glottis. Next, the boundary element method and the Kirchhoff–Helmholtz integral equation were used for discretization and to represent the wave equation for sound propagation, respectively. As a result, the relative discrimination thresholds of the vowel formant frequencies for /i/ and /u/ against actual voice were 1.1–10.2% and 0.4–9.3% for the first formant and 3.9–7.5% and 5.0–12.5% for the second formant, respectively. In the vocal tract model with nasal coupling, a pole–zero pair was observed at around 500 Hz, and for both /i/ and /u/, a pole–zero pair was observed at around 1000 Hz regardless of the presence or absence of nasal coupling. Therefore, the boundary element method, which produces solutions by analysis of boundary problems rather than three-dimensional aspects, was thought to be effective for simulating the Japanese vowels /i/ and /u/ with high validity for the vocal tract models encompassing a wide range, from the frontal sinuses to the trachea, constructed from CT data obtained during sustained phonation.
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