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11.
Min Jeong Noh Tae Gyun Kim In Kwon Hong Ki-Pung Yoo 《Korean Journal of Chemical Engineering》1995,12(1):48-55
A new transparent microscale circulation-type high pressure equilibrium cell with on-line sampling was devised. With this
apparatus, experimental solubility of molecularly complex species such as steroids (cholesterol, stigmasterol and ergosterol)
and fatty acids (palmitic acid and stearic acid) in supercritical carbon dioxide(sc-C02) were measured. Also, to find an appropriate substance for enhancing both the polarity and the solubility power of the SC-CO2 solvent, we arbitrarily selected three polar substances such as acetone, methanol and water and the effect of these cosolvents
on the solubility of solutes in SC-CO2 are examined. The supercritical phase equilibrium data of solute-cosolvent-sc-CO2 systems were quantitatively correlated using a new equation of state based on the lattice fluid theory incorporated with
the concept of multibody interaction. We found that the addition of tracer amount of acetone or methanol to SC-CO2 enhances the solubility of all solutes about thirty to sixty times when compared with the case of pure sc-CO2 However, for the case of cosolvent water, no further enhancement of the solubility of solutes was realized. Also, the versatile
fittability of the equation of state proposed in this work was demonstrated with the newly measured ternary supercritical
equilibrium data. 相似文献
12.
Won Tae KimCheolho Bai Young I. Cho 《International Journal of Heat and Mass Transfer》2002,45(3):597-607
The present study introduces a new experimental method to visualize the fouling process of CaCO3. A mini-channel heat exchanger system with a microscopic imaging technique was developed for real-time visualization of the fouling process. The present study discussed how scale started initially, how scale formed thick layers, and how a small crystal grew into a large one, touching the adjacent one. Detail microscopic images of scale crystals and corresponding fouling resistances were obtained over the entire fouling process. The microscopic observation indicated that the fouling process could be divided into three stages: an induction period, a period of uniform generation of nuclei, and a period of uniform growth of scale. Sudden appearance of numerous small nuclei indicated the end of the induction period, a key event before the rapid increase in the fouling resistance. The present experimental method using microscopic images of the wet fouling process provides a valuable insight on the fouling mechanism. 相似文献
13.
In polyolefin processes the melt index (MI) is the most important control variable indicating product quality. Because of
the difficulty in the on-line measurement of MI, a lot of MI estimation and correlation methods have been proposed. In this
work a new dynamic MI estimation scheme is developed based on system identification techniques. The empirical MI estimation
equation proposed in the present study is derived from the 1
st
-order dynamic models. Effectiveness of the present estimation scheme was illustrated by numerical simulations based on plant
operation data including grade change operations in high density polyethylene (HDPE) processes. From the comparisons with
other estimation methods it was found that the proposed estimation scheme showed better performance in MI predictions. The
virtual sensor model developed based on the estimation scheme was combined with the virtual on-line analyzer (VOA) to give
a quality control system to be implemented in the actual HDPE plant. From the application of the present control system, significant
reduction of transition time and the amount of off-spec during grade changes was achieved 相似文献
14.
Fast DCT algorithm with fewer multiplication stages 总被引:1,自引:0,他引:1
Yeonsik Jeong Imgeun Lee Hak Soo Kim Kyu Tae Park 《Electronics letters》1998,34(8):723-724
A novel fast DCT scheme with reduced multiplication stages and fewer additions and multiplications is proposed. The proposed algorithm is structured so that most multiplications tend to be performed at the final stage, which reduces the propagation error that could occur in the fixed-point computation. Minimisation of the multiplication stages can further decrease the error 相似文献
15.
Byeong Il Noh Tae Kyung Yoon Byung Hyun Moon Jong Hyun Kim 《Korean Journal of Chemical Engineering》1995,12(1):18-22
Multicomponent mass transfer accompanied by instantaneous chemical reactions in a small drop has been modeled and simulated
for the case where two different solutes diffuse from a continuous phase into the drop and react rapidly with a third reactant
in the drop. The computational results obtained by Galerkin’s finite element method are reported in terms of concentration
profiles, the locations of reaction front, the cumulative mass flux, and the enhancement factor. The effects of physical parameters,
such as diffusivities of the solutes and the reactant, the interfacial concentration of solutes, and the relative amount of
the reactant, on the calculated quantities are discussed. 相似文献
16.
The implementation of TS MAC system for KOREASAT DBS (direct broadcast satellite) system is presented. This TS MAC controls and monitors the status of the TS equipment and gathers the alarm for them. The advantage of this system is the center-concentrated, real time processing, remote control, and object oriented module decomposing 相似文献
17.
The objectives of this paper are to quantify the effect of Marangini convection on the absorption performance for the ammonia–water absorption process, and to visualize Marangoni convection that is induced by adding a heat transfer additive, n-octanol. A real-time single-wavelength holographic interferometer is used for the visualization using a He–Ne gas laser. The interface temperature is always the highest due to the absorption heat release near the interface. It was found that the thermal boundary layer (TBL) increased faster than the diffusion boundary layer (DBL), and the DBL thickness increased by adding the heat transfer additive. At 5 s after absorption started, the DBL thickness for 5 mass% NH3 without and with the heat transfer additive was 3.0 and 4.5 mm, respectively. Marangoni convection was observed near the interface only in the cases with heat transfer additive. The Marangoni convection was very strong just after the absorption started and it weakened as time elapsed. It was concluded that the absorption performance could be improved by increasing the absorption driving potential (xvb−xvi) and by increasing the heat transfer additive concentration. The absorption heat transfer was enhanced as high as 3.0–4.6 times by adding the heat transfer additive that generated Marangoni convection. 相似文献
18.
The humidity response characteristics of La doped BaTiO3 with different sintered densities and room temperature electrical conductivities were investigated using complex impedance measurement. The samples with low density and high resistivity showed the large and nearly linear sensitivity to the change of humidity. The impedance spectra of samples, when exposed to high humidity, can exhibit microstructure-related features, even though they do not give rise to a noticeable characteristic change when exposed to low humidity. The observed impedance patterns were dependent upon the density, and hence the oxidation kinetics of BaTiO3. 相似文献
19.
Kyeong Joong Kim Jong-Yeul Suh Moon Gi Kang Kyu Tae Park 《Electronics letters》1998,34(13):1302-1303
The boundary is approximated by a polygon which can be encoded with the smallest number of bits for maximum distortion. The temporal redundancy between two successive frames is efficiently removed with the proposed scheme, resulting in a lower bit rate than the conventional algorithms 相似文献
20.
Keon Woo Kang Jaemin Ann Hwang Soo Lee 《Electronics letters》1994,30(25):2153-2154
The authors propose a method to estimate the synchronisation offset for orthogonal frequency division multiplexing (OFDM) frame alignment without resort to pilot tones. A decision-directed maximum-likelihood estimation of frame synchronisation offset is derived, and the performance of the proposed scheme is confirmed by computer simulation for QAM systems 相似文献