Operability diagram of drop formation and its response to temperature variation in a piezoelectric inkjet nozzle

The present study has focused on the operability diagram of drop formation and its response to temperature variation in an inkjet nozzle driven by a piezoelectric actuator. As an operating fluid, ethylene glycol was used, and square wave pulses were applied to the nozzle in the present experiments. The operability diagram was constructed in driving voltage and pulse width space by changing the operating temperature from 30 °C to 50 °C. Four distinct types of drop response have been uncovered and are summarized in the operability diagram. The four types of response include single primary drop formation, drop formation with satellites, nozzle wetting without drop formation, and emission of a random spray. From the operability diagram, W-shaped regime of single primary drop was found, which was enlarged as temperature increased. Furthermore, the time scale of the W-shaped regime is closely related to the optimal pulse width and meniscus oscillation period of the present inkjet nozzle. In addition, it was found that by increasing the driving voltage and temperature, the size of single primary drop is increased due to the reduction in viscosity and contact angle of the operating liquid.     

Multiphysics neuron model for cellular volume dynamics

Even though cellular volume dynamics has been linked to cell apoptosis and intrinsic optical signals, there is no quantitative model for describing neuronal volume dynamics on the millisecond time scale. This study introduces a multiphysics neuron model, where the cell volume is a time-varying variable and multiple physical principles are combined to build governing equations. Using this model, we analyzed neuronal volume responses during excitation, which elucidated the variety of optical signals observed experimentally across the literature. Several physiological conditions were examined to investigate their effect on the pattern of volume response. In addition, we analyzed volume responses on a longer time scale with repetitive stimulation to study the characteristics of slow cell swelling. This multiscale analysis of the multiphysics model will provide not only a novel quantitative elucidation of physiologically important issues related with cellular volume dynamics but also a chance for further studies, such as the interesting possibility of inferring the balance of ion flux from plateau volume changes.     

Simulation study of biobutanol production in a polymer-loaded two-phase partitioning bioreactor (PL-TPPB): Simulation and strategy for biobutanol production

A simulation study was performed for a two-phase partitioning bioreactor (TPPB) with polymer beads, Dowex Optipore L-493, as a second phase. When the initial glucose concentration is less than 30 g/L, a single-phase bioreactor is preferred, because it consumed all the glucose with 40% of biobutanol yield. Any glucose over the concentration remained in the single-phase bioreactor because cells were completely inhibited by products, mainly biobutanol, and thus glucose availability became less than 100%. The TPPB with 10% polymer beads completely consumed up to 120 g/L glucose and more polymer beads were required for the higher glucose concentration. Instead of increasing the proportion of polymer beads, 2 vvm of nitrogen gas was introduced continuously into the TPPB for the stripping of products, reducing product inhibitions. By applying gas stripping to the TPPB containing 10% polymer beads, 150 g/L of glucose was completely consumed and 99.7% acetone, 46.8% butanol and 82.5% ethanol was stripped out of the TPPB. Finally, on the basis of these estimations, a novel strategy based on the initial glucose concentration was suggested for high biobutanol production.     

Lipase from Penicillium camembertii KCCM 11268: Optimization of solid state fermentation and application to biodiesel production

Lipase was produced by Penicillium camembertii KCCM 11268 under solid state fermentation (SSF), and the production process was optimized by using statistical experimental designs. The initial moisture content, cultivation time, inoculum size and concentration of basal medium were considered as the factors of optimum conditions for SSF. P. Camembertii KCCM 11268 was cultivated in SSF using wheat bran as the substrate for lipase production. Under the optimized condition, lipase activity was reached around 7.8 U/ml after eight days fermentation. To partially purify the lipase, ammonium sulfate (80% saturation) was added to the crude lipase solution and concentrated using a diafiltration (VIVAFLOW 50). The concentrated lipase solution from P. Camembertii KCCM 11268 (PCL) was immobilized on silica gel by cross-linking method. Also, PCL was mixed with a commercial lipase solution from Candida rugosa (CRL), and this mixture was co-immobilized on silica gel. The immobilized and co-immobilized lipase activities were 1150.1 and 7924.8 U/g matrix, respectively. Palm oil and methanol were used as substrates and 1mmol of methanol was added every 1.5 h and 2 times during biodiesel production. The reaction was carried out at temperatures of 30, 40, 50, 60 and 70 °C. The maximum biodiesel conversion by co-immobilized lipase was 99% after 5 h at 50 °C.     

OPTIMAL FED-BATCH OPERATION FOR RECOMBINANT CELLS WITH SEGREGATIONAL PLASMID INSTABILITY

Complete analyses of optimal solutions of fed-batch fermentation are provided for recombinant product maximization for free and fixed final times and constant and variable yield coefficients when the specific product formation rate π is in the form of the Leudeking-Piret equation. In all cases, feedback forms of singular feed rates are obtained, although one or two parameters must be introduced for variable yields. The precise conditions for existence of singular feed rate are obtained and characterized in terms of the ratio of the specific growth rate of the plasmid-bearing cell (PBC) to that of the plasmid-free cell (PFC), μ⁺/μ^?, and the specific growth rate of PBC, μ⁺. Thus, the inspection of the specific rates leads immediately if a singular feed rate is a part of the optimal feed rate strategy. When π is linear with respect to μ and the yield coefficient is constant, the optimal singular feed rate forces the substrate concentration to start near the value at which μ⁺ is maximum and moves in time in the direction of maximizing μ⁺/μ^?.     

Sulfur/graphitic hollow carbon sphere nano-composite as a cathode material for high-power lithium-sulfur battery

The intrinsic low conductivity of sulfur which leads to a low performance at a high current rate is one of the most limiting factors for the commercialization of lithium-sulfur battery. Here, we present an easy and convenient method to synthesize a mono-dispersed hollow carbon sphere with a thin graphitic wall which can be utilized as a support with a good electrical conductivity for the preparation of sulfur/carbon nano-composite cathode. The hollow carbon sphere was prepared from the pyrolysis of the homogenous mixture of the mono-dispersed spherical silica and Fe-phthalocyanine powder in elevated temperature. The composite cathode was manufactured by infiltrating sulfur melt into the inner side of the graphitic wall. The electrochemical cycling shows a capacity of 425 mAh g⁻¹ at 3 C current rate which is more than five times larger than that for the sulfur/carbon black nano-composite prepared by simple ball milling.     

Ferroelectric Photocurrent Effect in Polycrystalline Lead‐Free (K0.5Na0.5)(Mn0.005Nb0.995)O3 Thin Film

We deposited (K_0.5Na_0.5)(Mn_0.005Nb_0.995)O₃ (KNMN) thin films on Pt(111)/TiO₂/SiO₂/Si(100) substrates with a top electrode of indium tin oxide and investigated photocurrent properties in the wavelength range of 300?400 nm. Before the photocurrent measurement, the KNMN film was poled by applying a DC voltage. The photocurrents strongly depend on the wavelength of the incident photon energy. The photocurrents of the first measurement with poling in the up (?5 V) and down (+5 V) states were 21 and 3.2 nA/cm², respectively, at 344 nm. The difference in the photocurrents in both poling directions was explained by a space charge due to an asymmetric Schottky barrier height, which was caused by an internal electric field and polarization in the KNMN thin film.     

Effect of FeO Concentration on the Crystallization of High‐Temperature CaO–Al2O3–MgO–FeO Melts

Continuous cooling transformation (CCT) and time–temperature transformation (TTT) diagrams were plotted for CaO–Al₂O₃–MgO–FeO melts, and the morphology of the primary crystals formed was determined with a confocal laser scanning microscope (CLSM). When the CaO/Al₂O₃ ratio is 1.0, the crystallization temperature and incubation time increase with increasing MgO content. The TTT curve at 7.5 mass% MgO has a “C” shape, which facilitates the formation of amorphous phases. However, increasing the FeO content accelerated the crystallization time and lowered the crystallization temperature. The solidified melt with an FeO content of less than 10 mass% was a combination of the C₃MA₂ and C₅A₃ phases; higher FeO content led to the formation of a secondary phase of Ca₂FeAlO₅ and CA following the precipitation of the C₃MA₂ primary phase. In addition, kinetic evaluation of the crystal growth with confocal micrographs indicated that the calculated crystal volume agreed well with the Johnson–Mehl–Avrami sigmoidal curve fit.     

Experimental study of honeycomb regenerator system for oxy-fuel combustion

An experimental study of a honeycomb regenerator for oxy-fuel combustion has been performed. A laboratory-scale test rig is set up and various experimental parameters such as cell density and length of the honeycomb regenerator, switching time, and bypass effect are investigated. The typical temperature trend of the heating and regenerating process is obtained for the oxy-fuel combustion. The regenerative characteristics for various combinations of these parameters are shown. It is found that part of the exhaust gas should be bypassed to use waste heat more efficiently and to optimize the efficiency of the honeycomb regenerator system for oxy-fuel combustion.