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This paper presents a coating model to predict the mass coating uniformity in a Wurster fluid bed coater using a Monte Carlo method. The velocity and voidage data obtained using imaging techniques on the same Wurster coater are used as inputs to the model. The semi-circular Wurster fluid bed used in this work was 22.9 cm in diameter. A batch of 3.6 kg tablets was used to conduct coating experiments and the coating weight gain distribution results were compared to predictions from the simulation. The model rigorously considers the sheltering effect of particles as they move in the spray zone. Good agreement was obtained when comparing the results with an analytical model.Spray shape and orientation of discretization were found to play an important role in predicting the coating uniformity. A simple spray experiment in a particle-free bed showed that the direction of spray material, in general, was vertically upward. Simulation results confirmed that an upward cylindrical spray model gives better agreement with experimental results compared to a solid cone spray model. Finally, the model was used to predict the changes in coating uniformity with bed operating conditions such as gas velocity and gap height. A wider coating distribution was found for the case with the lower gas velocity and gap height. 相似文献
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海底天然气渗漏地震探测方法的研究进展 总被引:6,自引:0,他引:6
海底天然气渗漏可以指示沉积层中的烃类聚集带,渗漏出的大量气体(主要是甲烷)还可能影响全球的气候变化。此外,与海底渗漏相关的浅层气改变了海底沉积物的土工性质,可能对海底工程构成威胁。因此对海底天然气渗漏进行研究意义重大。在海底渗漏探测方面,地震是一种有效的方法,它不仅能反映深部构造,为海底渗漏提供气体来源和运移通道信息;而且还可以直接用来寻找渗漏相关特征,为海底观测和取样提供依据。在地震剖面上,与海底天然气渗漏相关的浅层气表现为声混浊、声空白、亮点、多次波、速度下拉、气烟囱等特征,泥火山、泥底辟表现为隆起的地震透明带,而麻坑则表现为“V”字形截面和半透明状地震混浊。 相似文献
115.
Young-Hwan You Won-Gi Jeon Jong-Ho Paik Dae-Ki Hong Hyoung-Kyu Song 《Broadcasting, IEEE Transactions on》2003,49(4):354-361
In this paper, an OFDM-CDMA system employing various diversity schemes is considered for a possible candidate of broadband wireless access networks and broadcasting applications. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation based on the time-domain windowing and its imperfectness in OFDM-based multiple-antenna transmission systems. By properly designing each preamble for multiple antennas to be orthogonal in the time domain, the channel estimation can be applied to the HIPERLAN/2 and IEEE 802.11a standards in the case of more than two transmit antennas. Also, the effect of diversity techniques on the performance of OFDM-CDMA based broadband wireless access networks is investigated and the maximum achievable diversity gain for a two-path Rayleigh fading environment is evaluated. Simulation results show that the OFDM-CDMA system applying a space-time-frequency diversity with a full-rate full diversity code can give the diversity of D=4 and D=8 for both multi-user cases of maximum user and half user capacities, respectively. 相似文献
116.
M.H. Song B. Park S. Nishimura T. Toyooka I.J. Chung Y. Takanishi K. Ishikawa H. Takezoe 《Advanced functional materials》2006,16(14):1793-1798
A liquid crystal (LC) photonic device with an anisotropic optical heterojunction structure has been fabricated. The device has a phase‐retarding nematic LC (NLC) layer sandwiched between two polymer cholesteric LC films with right‐handed helices of different pitches. Electrotunable non‐reciprocal light transmittance and unidirectional circularly polarized (CP) lasing emission have been successfully demonstrated for this device structure. Two left CP (LCP) lasing emission peaks are observed at the edges of the overlapping region between the two photonic bands in the structure and are shifted upon the application of a voltage. In contrast, a non‐reciprocal right CP (RCP) lasing emission peak emerges at one of the band edges and diminishes upon the application of a voltage. These phenomena are interpreted based on the selective reflection of RCP light and the reorientation of the NLC molecules by the application of a voltage. 相似文献
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A very general model formulation is presented in the frequency domain for the pulse-echo ultrasonic response of an arbitrary scatterer in a fluid. The transducer is modeled as a piston source and the scatterer can be located anywhere in the transducer wavefield. The model is computationally efficient and is shown to agree well with initial experiments. 相似文献
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