JOURNAL OF CHEMICAL ENGINEERING OF JAPAN
Online ISSN : 1881-1299
Print ISSN : 0021-9592
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Volume 31, Issue 4
Displaying 1-27 of 27 articles from this issue
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Thermodynamics, Physical Properties and Molecular Simulation
  • An Improved Model of Second Virial Coefficients for Polar Fluids and Fluid Mixtures
    Ming-Jer Lee, Jui-Tang Chen
    1998 Volume 31 Issue 4 Pages 518-526
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.518
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    A corresponding-states model was developed empirically for calculating the second virial coefficients of polar fluids and fluid mixtures. In this model, a “nonpolar” and a “polar” acentric factors characterize size/shape and polarity/association effects, respectively. The new model contains a polarity or an association parameter (αP or αHB), which can be estimated from fluid’s reduced dipole moment through a specific generalized correlation. The temperature function of association contribution was found to depend on fluid’s reduced dipole moment. This generalized model predicts well the second virial coefficients for a diversity of polar fluids and strongly hydrogen-bonded substances. The new model with a set of recommended kij’s can reasonably estimate the second virial cross-coefficients.
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  • Knudsen Diffusion in the Sequentially Linked Spherical Pore
    Soong-Hyuck Suh, Nam-Ho Heo, David Nicholson
    1998 Volume 31 Issue 4 Pages 644-648
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.644
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    Molecular dynamics (MD) simulations have been carried out to investigate the Knudsen diffusion properties for the non-adsorbed, collisionless molecules confined within the one-dimensional model pore system, namely, the sequentially linked spherical pore. Simulation results were used to evaluate various theoretical calculations appeared in the literature including the random walk approximation, the radiating disc method, and the molecular path tracing method. The simple equation based on the molecular path tracing method, in comparison with MD simulation results, has proven to be successful to qualitatively and quantitatively predict the diffusion coefficient in the Knudsen regime over the entire ranges of the pore cross-sectional variations in such a model system.
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  • Measurement and Prediction of Mutual Diffusion Coefficients for Acrylic Adhesive-Methyl Propyl Ketone System
    Shigetoshi Kobuchi, Makoto Kumada, Kenji Fujimura, Hideaki Komatsubara ...
    1998 Volume 31 Issue 4 Pages 663-666
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.663
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    Mutual diffusion coefficients for an acrylic adhesive-methyl propyl ketone system were measured at 313.15 K, 323.15 K and 333.15 K by using a sorption and desorption method, and are predicted by the free volume theory of Duda et al. which was modified by Iwai et al. The six model parameters out of eight required to predict the mutual diffusion coefficients are estimated by adopting a previous method from the physical properties of methyl propyl ketone. The predicted values are in fairly good agreement with the experimental results.
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  • Correlation of Infinite Dilution Activity Coefficients of 1- and 2-Alkanols in Tetradecane and Hexadecane Using Modified ASOG
    Kenji Fukuchi, Toru Watanabe, Setsuko Yonezawa, Yasuhiko Arai
    1998 Volume 31 Issue 4 Pages 667-669
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.667
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    ASOG (Analytical Solution of Groups), which is widely applied to predict the liquid-phase activity coefficients of solutions, is extended to be capable to distinguish isomers. The Flory-Huggins (FH) part is examined by using the infinite dilution activity coefficient data of n-alkane binary mixtures and an empirical equation is proposed to modify the number of carbons contained in the n-alkanes. The concept of effective carbon number is adopted to apply the empirical equation to components other than n-alkanes. To evaluate the number of group, in the group interaction part, the contact probability is introduced, in which a steric hindrance factor is incorporated. The present model can give a good correlation for the infinite dilution activity coefficients of 1- and 2-alkanols in tetradecane and hexadecane.
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Transport Phenomena, Fluid Mechanics and Mixing
  • Influence of Tank Bottom Shear Stress on Complete Fluidization of Spherical Solid Particles in a Square Surface Agitation Tank
    Hitoshi Takase, Hajime Unno, Takashi Akehata
    1998 Volume 31 Issue 4 Pages 657-662
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.657
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    The influence of tank bottom shear stress on complete fluidization of spherical solid particles in a square surface agitation tank is investigated. The shear stress on the tank bottom is measured by the electrochemical method, which utilizes the reduction of dissolved oxygen on point electrodes embedded in the tank bottom.
    The shear stress has a different value for each point electrode. It is found that complete fluidization of particles is attained when the shear stress all over the tank bottom exceeds the minimum shear stress required for the fluidization of particles, which is dependent on the properties of the particle and surrounding liquid in the tank. The empirical equation, which shows the relationship between the minimum shear stress required for the fluidization of particle and the properties of particle and liquid in the tank, is obtained. By use of this equation, the relationship between the minimum impeller speed required for complete fluidization and experimental conditions is further discussed.
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Catalysis, Kinetics and Reactor Design
Separations
  • Direct Contact Heat Transfer in Melt Crystallization
    Kwang-Joo Kim, Alfons Mersmann
    1998 Volume 31 Issue 4 Pages 527-535
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.527
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    The heat transfer of melt crystallization with direct contact coolants such as gas, liquid and vaporized liquid was explored. Melt crystallization with direct contact coolants was carried out by crystallizing n-dodecanol from n-decanol - n-dodecanol mixture. The direct cooled crystallizers were capable of being operated either batch-wise or continuously. The superficial velocity of coolant: 3 × 10–6–2 × 10–4 m/s for the vaporized liquid, 1 × 10–5–1 × 10–4 m/s for the liquid and 5 × 10–2–2 × 10–1 m/s for the gas, and the hold-up of coolant: 0.02–0.9 for the liquid and 0.01–0.25 for the gas were varied. The volumetric heat transfer coefficient obtained by direct contact cooling in the melt crystallizer was varied in the range of 0.1 to 100 kW/m3K. It was roughly proportional to the 1.5 to 1.8 power of the linear velocity of coolant. The semiempirical relations for correlating the volumetric heat transfer coefficient in the direct cooled melt crystallization were presented.
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  • A Mathematical Model of Internal Fouling in Protein Microfiltration
    Kazuho Nakamura, Kanji Matsumoto
    1998 Volume 31 Issue 4 Pages 536-544
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.536
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    A mathematical model for internal fouling in protein microfiltration is developed to correlate flux decline and protein transmission with protein adsorption on pore surface during filtration. The model was constructed based on the mass balance of protein in a small section of membrane assuming that multilayer adsorption occurs in the pore, which consists of primary adsorption of proteins on the clean surface and the secondary one on the adsorbed protein. The flux decline is evaluated by a pore narrowing model which considers protein adsorption. The previously reported experimental curves of flux decline and protein transmission rate are fairly well simulated by this model using six fitting parameters, which are adsorption capacity, adsorption coefficient, and thickness of adsorption layer, in both the primary adsorption and the secondary adsorption.
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  • Adsorption Properties of Metal Ions onto Sodium Polyacrylate Gel
    Shoichi Morohashi, Masashi Takaoka, Tetsuya Yamamoto, Kazuhiro Hoshino
    1998 Volume 31 Issue 4 Pages 551-557
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.551
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    Adsorption properties of divalent and trivalent metal ions onto sodium polyacrylate gel are investigated over a range of pH of buffer solutions. It is considered that carboxyl groups in the gel combine with the metal ions according to their charge number stoichiometrically, and the adsorption mechanism is theoretically analyzed on the basis of dissociation equilibrium for monocarboxyl acid. Furthermore, it is found that the adsorption effectiveness factor, being intrinsic to metal ion species, fulfills an important role in order to elucidate the adsorption equilibrium. Consequently, the model equations, which allow quantitative consideration of the adsorption mechanism in these systems, can be derived as a function of the hydrogen ion concentration, which can readily be measured in the outer aqueous solution. The gel adsorption equilibrium of divalent and trivalent metal ions can be explained fairly well by the model.
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  • Constant Pressure Filtration of Suspension in Viscoelastic Fluid
    Kuo-Jen Hwang, Chi-Yu Huang, Wei-Ming Lu
    1998 Volume 31 Issue 4 Pages 558-564
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.558
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    The mechanism of constant pressure filtration of particle suspension in a viscoelastic fluid is studied. Effects of operating conditions on the performance of filtration are discussed. At the beginning of a filtration, the elastic behavior of fluid plays an important role on the performance of filtration, which results in a more compact cake and increases filtration resistance. After a period of time, the elastic effect diminishes gradually, and the flow behavior of fluid transforms to power law due to the decrease of filtration rate. A numerical program based upon the continuity equation of cake compression and the filtration equation is designed for simulating the variations of local cake properties during a course of constant pressure filtration. The average cake porosity decreases with time at the beginning of filtration and then increases and approaches to a given value when the flow behavior transforms to power law. The calculated results of average cake porosity agree very well with the experimental data when the filter chamber is filled with cake.
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  • Dehydrogenation of Pure Cyclohexane in the Membrane Reactor and Prediction of Conversion by Pseudo Equilibrium Model
    Takao Kokugan, Azis Trianto, Hiromichi Takeda
    1998 Volume 31 Issue 4 Pages 596-603
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.596
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    Three kinds of membrane reactor, porous Vycor glass, ceramic Sol-gel, and Palladium-silver membrane reactors, are used to study the dehydrogenation of pure cyclohexane. The reactors are intended to be applied as chemical heat pumps, therefore they were fed with pure cyclohexane. The experimental results show that the higher conversions exceeding the equilibrium one, αeq = 6.4%, were achieved up to 27% and 11% for Pd-Ag (PT-2), and porous Vycor glass membranes respectively. A pseudo equilibrium (PE) model was proposed to predict the conversion achieved in the reactor. In the Damkohler number (Da) range employed of 1.05–4.48, the model is in good agreement with the experimental results. The prediction becomes less accurate with increasing pressure difference.
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  • Selective Recovery of Proteins by Control of Their Surface Properties Utilizing PEG-Bound Affinity Ligands
    Ryoichi Kuboi, Tetsuhiro Hasegawa, Katsuhito Yamahara, Isao Komasawa, ...
    1998 Volume 31 Issue 4 Pages 618-625
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.618
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    Selective recovery of proteins by control of their surface properties is investigated by using a ligand modified aqueous two-phase system (ATPS) and polyethylene glycol (PEG) precipitation. The ligands used were nonionic surfactant (Triton and PEG-palmitate) and PEG-bound dye (Cibacron Blue and Procion Yellow). Both the partition coefficient in ATPS and the solubility in a PEG solution of Bovine Serum Albumin (BSA) increase significantly with the addition of these ligands, because the surface net hydrophobicity of BSA is increased by the binding of these hydrophobic ligands. On the other hand, these ligands have no effect on the partition behavior and solubility of Carbonic Anhydrase (CAB) and Ovalbumin (OvA), which have no binding sites to the ligands. Control of the surface properties of protein by these specific bindings of ligands can be utilized to improve the separation efficiency in ATPS and PEG precipitation. A separation process using ligand modified ATPS and PEG precipitation is developed.
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  • Measurement of Temperature Dependence of Cyclodextrin Binding Constant Using Ultrafiltration
    Takao Kokugan, Arif Yudiarto, Tadashi Takashima, Erwana Dewi
    1998 Volume 31 Issue 4 Pages 640-643
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.640
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    The temperature dependence of the binding constant KB for cyclodextrin (CD) and nitrophenol (NP) system is investigated using a previously proposed method. The method is based on the selective inclusion property of cyclodextrin (CD) and the selective permeability of the ultrafiltration membrane (UF/m). KB decreases with increasing temperature. Meanwhile, the activation energy of binding (ΔET) is calculated from the Arrhenius plot and it is a negative value. The absolute values of ΔET become large in the order of o-, m-, and p-NPs. These values approximately agree with those of other investigators who employed other methods. Furthermore, the forcible binding energy ΔEF is calculated from the pressure (Pd), where the rise ratio of rejection (η) begins deviating from the constant value which is measured at lower pressure. ΔEF agrees with ΔET. The ratio of ΔET to ΔEF is nearly constant at 7, and independent of pH and the reaction system.
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  • Pervaporation Characteristics of Water and 2-Propanol in Sulfonated Polyethersulfone Membranes
    Toyozo Hamada, Takaaki Hoshikawa, Setsuji Tone
    1998 Volume 31 Issue 4 Pages 652-656
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.652
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    Pervaporation behaviors of water–2-propanol mixtures are examined using a polyethersulfone (PES) membrane and four kinds of sulfonated polyethersulfone (SPES) membranes with various contents of sulfonate groups. The fluxes of water and 2-propanol increase with increasing mole fraction of sulfonate group, s, in the membrane.
    Based on the solution-diffusion theory by considering water solubilities in the membranes, the fluxes of water and 2-propanol through these membranes were analyzed. There is no significant difference in the values of diffusion coefficients without swelling and the swelling parameters for water and 2-propanol among these membranes. It is found that the separation factors for various SPES membranes can be estimated from the parameter values for PES membrane by expressing the mole concentration in the membrane using the s value.
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Particle Technology and Fluidization
  • Characteristics and Production Mechanism of Sulfuric Acid and Nitric-Hydrofluoric Acid Pickling Sludge Produced in Manufacture of Stainless Steel
    Masahiko Ito, Rinso Tachibana, Katsuji Fukushima, Yoshikazu Seino, Aki ...
    1998 Volume 31 Issue 4 Pages 589-595
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.589
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    Stainless steel pickling sludge consists largely of surface scale from stainless steel strips, being composed mainly of Cr oxides. Moreover, the present work shows that the Cr concentration of the sludge is approximately twice that of ordinary stainless steels. The particle size of sulfuric acid sludge is 0.325 μm, while that of nitric-hydrofluoric acid sludge is 9.2 μm. Nitric-hydrofluoric acid sludge tends to coagulate in a relatively short time, while sulfuric acid sludge essentially does not tend to coagulate. The main components of sulfuric acid sludge and nitric-hydrofluoric acid sludge are FeCr2O4 and Cr2O3. In the mechanism of sludge precipitation in the pickling process, acid penetrates cracks in the scale and dissolves part of the scale and the substrate. The undissolved scale then loses the ability to bond with other scale and the substrate and settles out in the pickling tanks.
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  • Solids Circulation Rate in Screen-Bottomed Spouted Bed with Draft-Tube
    Hirotsugu Hattori, Takashi Nagai, Yasutaka Ohshima, Mana Yoshida, Atsu ...
    1998 Volume 31 Issue 4 Pages 633-635
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.633
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    The solids circulation rate was measured in a spouted bed without a gas inlet nozzle or orifice, in which the gas was introduced from the screen bottom at uniform velocity over the cross section of the vessel, and compared with that in the nozzle or orifice inlet type spouted bed. The rate in the screen-bottomed spouted bed is significantly greater than that in the nozzle or orifice inlet type. It is found that gas flows from the annulus into the spout through the clearance between the lower end of the draft-tube and the gas inlet screen, and that such a gas flow pattern facilitates the solids circulation in the screen-bottomed spouted bed.
    It is a useful for a process in which a high rate of solids circulation is required.
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Process Systems Engineering
  • Self-Tuning Control of Batch Polymerization Reactor
    Sabahat Erdogan, Gülay Özkan, Mustafa Alpbaz
    1998 Volume 31 Issue 4 Pages 499-505
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.499
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    The optimal temperature control of a batch jacketed free radical polymerization reactor with self-tuning PID and conventional PID control methods are considered. The controller is implemented on a digital computer to track precalculated optimal temperature trajectories obtained for different initiator initiation concentration in a batch styrene polymerization reactor. The performance of the self-tuning controller is compared against that of a PID controller. Self-tuning controller provides good, robust control in despite of the nonlinear dynamics of the polymerization reactor system.
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  • Structured PENN Controller for MIMO Process
    Takehiro Ohba, Masaru Ishida
    1998 Volume 31 Issue 4 Pages 545-550
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.545
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    This paper presents a neural net controller for a multi-input, multi-output (MIMO) process. The controller is based on the PENN (Policy- and Experience-driven Neural Network) method. The PENN uses two types of knowledge for learning: local experiences obtained from the control results; and global policies based on rule-based control strategy. The structured PENN that is proposed for a MIMO process in this study has a structure in which small controllers for SISO processes are assembled. By use of such a structured assembly, both learning and control for a MIMO process can be accomplished. To prevent the effect of noises observed in the controlled variables, a noise reduction mechanism modifying the error function in the learning algorithm is proposed. The simulation results for a crystal growth process indicate that the proposed controller has the ability to learn the interactions between control variables and to get satisfactory control results.
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  • Identification of Wiener Model Using Relay Feedback Test
    Hsiao-Ping Huang, Ming-Wei Lee, Yeong-Tarng Tang
    1998 Volume 31 Issue 4 Pages 604-612
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.604
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    A method for identifying a wiener-type model for nonlinear processes is proposed. The linear subsystem of the model is represented by simple transfer functions of the form such as: FOPDT (i.e. First-Order-Plus-Dead-Time) or an SOPDT (i.e. Second-Order-Plus-Dead-Time). The static nonlinearity is represented by an invertible function defined on an operation domain. Data from a two-stage relay feedback experiment in one single run is required. Simple algorithms are formulated to identifying both structure and parameters of the model. Estimation of parameters in both linear and nonlinear parts is performed separately and in an one-by-one sequence.
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  • Auto-Tuning PID Controller Based on Generalized Minimum Variance Control for a PVC Reactor
    Norio Miura, Masao Imaeda, Kyoji Hashimoto, R. K. Wood, Hirofumi Hatto ...
    1998 Volume 31 Issue 4 Pages 626-632
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.626
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    The control of PVC reactors is usually accomplished by using a PID control algorithm, despite attempts at using different advanced control algorithms and strategies. This paper presents simulation results from the application of a PID on-line auto-tuning controller based on robust adaptive control theory. PVC reactor control performance achieved using the combined PID auto-tuning controller is compared with that obtained using a conventional fixed parameter PID algorithm. Stable control behavior is achieved, and the response settles quickly with the PID controller parameters adapted to achieve generalized minimum variance control. Also, a method for estimating the turning point in a polymerization process is proposed.
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Biochemical, Food and Medical
  • Relation between Thermal Stabilizing Effect of Sucrose on LDH and Sucrose-LDH Hydrogen Bond
    Tetsuo Suzuki, Koreyoshi Imamura, Hiroki Fujimoto, Morio Okazaki
    1998 Volume 31 Issue 4 Pages 565-570
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.565
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    The thermal stabilizing effect of sugar on freeze-dried protein is studied, in particular on the relationship between the thermal stabilizing effect and the degree of sugar-protein hydrogen bond formation. Sucrose and lactate dehydrogenase (LDH) are used as models for sugar and protein. Several freeze-dried samples of LDH involved in sucrose were prepared; they differed in the degree of crystallinity of sucrose. By X-ray diffractometry (XRD) and Fourier transform infrared (FT-IR) spectroscopy, it is found that when sucrose is amorphous in the samples, the degree of hydrogen bond formation is high and LDH is stabilized remarkably. In contrast, when sucrose is crystalline, the degree of hydrogen bond formation is low and LDH is inactivated. These results indicate that the stabilizing effect of sugar is closely related to the sugar-protein hydrogen bond. The influence of sucrose content on the thermal stabilizing effect is also investigated. It is found that there is an optimum sucrose content for the thermal stabilizing effect. This is because, by the presence of LDH, the amorphous structure of sucrose is stabilized and protected from crystallization that causes loss of sucrose-LDH hydrogen bonds. Thus, we can deduce that sugars and proteins work together to maintain protein activities.
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  • Evaluation of Photocatalytic Sterilization Rates of Escherichia coli Cells in Titanium Dioxide Slurry Irradiated with Various Light Sources
    Yasuhiko Horie, Masahito Taya, Setsuji Tone
    1998 Volume 31 Issue 4 Pages 577-584
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.577
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    Photocatalytic sterilization of Escherichia coli cells with TiO2 particles is examined using a rectangular bubble-column reactor irradiated with three kinds of artificial light sources. The three types of used lamps were a black light fluorescent (BL-F) lamp, a blue actinic fluorescent (BA-F) lamp and a daylight fluorescent (DL-F) lamp. Under the conditions of TiO2 concentration of 1 × 10–2 kg/m3 and initial cell concentration of 1 × 1011 cells/m3, average light intensities in the reactor were varied in the range of 0 to 22 W/m2, 0 to 14 W/m2 and 0 to 1.1 W/m2 with the BL-F, BA-F and DL-F lamps, respectively. The apparent sterilization rate constants of E. coli cells for these lamps are determined on the basis of a series-event model, and are compared with those obtained in experiments with a high pressure mercury lamp. Irrespective of the examined lamps, the rate constants can be correlated with the light quantities absorbed by TiO2 slurry, which are evaluated by taking into account both the dependency of absorbance of TiO2 slurry on light wavelengths and the spectral distributions of light rays from the respective lamps. From the results obtained in experiments using the artificial light sources, the sterilization rate constants of E. coli under the sunlight can be predicted. The experimental data are in good agreement with the predicted results in the reactor illuminated with sunlight at average light intensities of 14 and 23 W/m2.
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  • Development of Rotating-Mesh Basket Type Bioreactor for Carrot Embryo Production in Immobilized Callus System
    Ken-ichiro Suehara, Eiji Nagamori, Hiroyuki Honda, Nobuyuki Uozumi, Ta ...
    1998 Volume 31 Issue 4 Pages 613-617
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.613
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    Mass-production of regenerated plantlets using alginate bead encapsulating carrot callus was studied. When gel beads were cultivated in a flask containing regeneration medium, somatic embryos were released at high frequency from the gel beads and developed into plantlets. When a callus less than 320 μm in size was immobilized in the beads, a larger number of embryo was released from the beads. At 0.11 ml-pcv/ml-gel of inoculum size, the maximum number of embryo was obtained. In order to develop a suitable bioreactor for the immobilized callus system, three types of bioreactors, namely air-lift, horizontally shaking vessel and rotating mesh-basket types, were tested. In the case of the rotating mesh-basket type, a larger amount of released cells was obtained. Plantlet formation from the released cells reached a level of 115% compared with that of the flask culture. To achieve continuous recovery of released cells and perform long term culture, a cyclone type cell separator was designed and used in conjunction with a rotating mesh-basket type bioreactor. When 110 ml/min of medium flow was passed through the separator, 90% of suspended cells were collected after 40 min of operation time. Long term cultures at 50, 100, and 150 rpm of rotational speed were carried out. In the experiment at 100 rpm, almost constant values of released cell volume and number of embryos were obtained during 12 d. They were 3 ml-pcv/l-medium/d and 7000 plantlets/g-released cells, respectively.
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  • Continuous Cultures of Spirulina platensis under Photoautotrophic Conditions with Change in Light Intensity
    Satoshi Hirata, Masahito Taya, Setsuji Tone
    1998 Volume 31 Issue 4 Pages 636-639
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.636
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    In continuous cultures of Spirulina platensis under photoautotrophic conditions, the operation mode to maintain constant cell concentration is examined using culture apparatuses with light path lengths of 0.02 and 0.156 m. The values of dilution rates in the continuous cultures are determined by employing specific growth rates of the cells corresponding to light intensity distribution in liquid medium. When incident light intensity is fixed at 25, 50 or 400 W m–2, it is found that the cell concentration in the continuous culture is kept almost constant, and agrees fairly well with the prescribed value of the cell concentration in the range of 0.09 to 2.43 kg m–3. It is also demonstrated that the operation mode is valid to obtain stable cell concentrations in the continuous cultures associated with the change in incident light intensity ranging from 25 to 400 W m–2 during the cultures.
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  • Surface Dissolution-Bulk Erosion Model of Drug Release from Biodegradable Polymer Rods
    Kakuji Tojo, Hisae Aoyagi, Tomonori Kurita
    1998 Volume 31 Issue 4 Pages 648-651
    Published: 1998
    Released on J-STAGE: April 26, 2004
    DOIhttps://doi.org/10.1252/jcej.31.648
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    A combined model of surface dissolution of the drug and bulk erosion of the polymer is developed for describing the biphasic release profile of drugs from biodegradable polymer rod devices. The model parameters are determined from the conventional moment analysis of the time course of the release profile. The model describes well the typical biphasic phenomena of drug release, the initial bursting release due to dissolution of the surface drug molecules, and the late bursting caused by the bulk erosion of biodegradable polymers.
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Safety, Environment and Energy
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