• Asian-Australasian Journal of Animal Sciences
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• v.13 no.7
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• pp.922-928
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• 2000

The effects of animal species and supplements on rumen fluid characteristics, plasma urea-N (PUN) concentration, plasma urea-N pool size, urea-N degradation in the gut and urea-N net flux (urea-N synthesis rate) were studied in goats and sheep, with some minor differences detected. The animals were fed either chopped rice straw ad libitum+200 g soybean meal (SBM), or chopped rice straw ad libitum+190 g soybean meal+300 g sago meal (SBM+SM) for 14 days. The supplements were isonitrogenous (80 g crude protein/animal/d). [$^{14}C$]-urea was used as the marker for urea metabolism studies. Two animals from each species were fed either supplement in a cross-over design in two periods. The results showed that rumen pH was significantly (p<0.001) lower in animals fed SBM+SM than those fed SBM supplement. The ammonia concentrations of rumen fluid were significantly (p<0.01) higher in sheep (382.9 mg N/L) than goats (363.1 mg N/L) when fed SBM supplement but lower (282.5 mg N/L) than that of goats (311.0 mg N/L) when fed SBM+SM supplement. Total VFA concentrations were significantly (p<0.05) higher in animals fed SBM+SM supplement than those fed SBM supplement. Goats had significantly (p<0.01) higher molar proportions of acetate (79.1, 77.7%, respectively) than sheep (75.8, 74.0%, respectively) in both supplements. The molar proportion of acetate was significantly (p<0.05) higher, while that of butyrate lower in animals fed SBM supplement than those fed SBM+SM supplement. In animals fed SBM supplement, the molar proportion of propionate was significantly (p<0.01) higher in sheep (18.0%) than in goats (15.6%), but in animals fed SBM+SM, the molar proportion of butyrate was significantly (p<0.01) higher (9.6%) in sheep than in goats (7.2%). Plasma urea-N concentration, plasma urea-N pool size, urea-N degradation in the gut, urea-N net flux and the fraction of urea-C from the blood entering the rumen were not significantly different between goats and sheep fed either supplement. However, PUN concentration was significantly (p<0.05) lower in animals fed SBM+SM supplement (average of 13.8 mg N/100 ml) than in those fed SBM supplement (average of 16.5 mg N/100 ml). The urea net flux was significantly (p<0.05) higher in goats (average of 14.5 g N/d) than sheep (average of 12.9 g N/d), and animals fed SBM supplement showed higher (average of 14.9 g N/d) urea net flux than animals fed SBM+SM supplement (average of 12.9 g N/d). A significant (p<0.05) positive correlation was observed between urea-N net flux and urea-N degradation; urea-N net flux and pool size; urea-N net flux and urea excretion in the urine; and PUN and rumen ammonia in goats. While in sheep, significant (p<0.05) positive correlation was observed between urea-N net flux and urea excretion in the urine; and PUN and rumen ammonia.

• Journal of Pharmaceutical Investigation
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• v.38 no.1
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• pp.31-38
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• 2008

The objective of this work is to study transdermal delivery of levodopa using iontophoresis and evaluate various factors which affect the transdermal transport. Levodopa is unstable in aqueous solution, and, in order to establish a stable condition for levodopa for the duration of experiment, we investigated the stability of levodopa in aqueous solutions of different pHs with/without the addition of dextrose or the application of current. Using stable aqueous solution, we have studied the effect of pH, polarity and penetration enhancer (ethanol) on transdermal flux and compared the results. We also investigated the iontophoretic flux from hydroxypropyl cellulose (HPC) hydrogel. In vitro flux study was performed at $33^{\circ}C$, using side-by-side diffusion cell. Full thickness hairless mouse skin and rat skin were used for this work. Current densities applied were 0.4 or $0.6mA/cm^2$ and current was off after 6 hour application. Stability study showed that levodopa solution with a pH 2.5 or 4.5 maintained the initial concentration of levodopa for 24 hours with the addition of 5% dextrose. However, at pH 9.5, levodopa was unstable and 30 to 40% of levodopa degraded within 24 hours, even with the addition of 5% dextrose. Hydrogel swollen with dextrose added levodopa solution maintained about 97% of the initial concentration of levodopa for 13 days, when stored in $4^{\circ}C$. The application of current did not affect the stability of levodopa in hydrogel. Flux study from levodopa solution with pH 2.5 showed that cathodal delivery of levodopa was higher than passive or anodal delivery. When the pH of the donor solution was 4.5, anodal delivery of levodopa was higher than passive or cathodal delivery. These results seem to indicate that electroosmosis plays more dominant role than electrorepulsion in the flux of levodopa at pH 2.5, and the reverse situation applies for pH 4.5. The passive flux was unexpectedly high for the ionized levodopa. Similar to the results from aqueous solution, cumulative amount of levodopa transported trom HPC hydrogel by cathodal delivery was significantly higher than passive or anodal delivery. The treatment of 70% ethanol cotton ball by scrubbing increased passive, anodal and cathodal flux, with the largest increase for anodal flux. These results indicate that iontophoretic delivery of zwitterion such as levodopa is much complicated than that can be expected from small ionic molecules with single charge. The results also indicate that the balance between electroosmosis and electrorepulsion plays a very important role in the transport through skin.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.608-613
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• 2017

We proposed a pyrometallurgical process to achieve gold alloy with an Au content of more than 80wt% from low grade (<35wt%) gold alloys. We performed the heat treatment at a temperature of $1200^{\circ}C$ for 5 hrs using Au35wt%-Ag5wt%-Cu60wt% gold alloys mixed with 1/2 weighed PbO and CaO flux by varying the ratio of PbO/(PbO+CaO) from 0 to 1. We investigated the change in content of the samples with energy dispersive X-ray spectroscopy (EDS) and time of flight secondary ion mass spectrometry (ToF-SIMS). The EDS results showed that the Au content increased from 35.0wt% in the PbO-only sample to 86.7wt% (in the PbO/(PbO+CaO) 1:1 sample), while the other samples achieved more that 84wt%. In addition, the 2/3 flux ratio sample showed the lowest Ag loss into the flux. In the ToF-SIMS results, the PbO only and CaO only fluxes had Au+ peak intensities of 349 and 37, respectively. Although the CaO-only flux might be more favorable considering the loss of Au into the flux, we concluded that the amount of Au lost into the flux could be ignored. Our results imply that that the pyrometallurgical process using a mixed flux is an effective hydrometallurgical process.

• Journal of Microbiology and Biotechnology
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• v.10 no.4
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• pp.441-448
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• 2000

The production and cation flux-mediated activation of the P-type ATPase in Helicobacter pylori was investigated. Using the polymerase chain reaction (PCR), the proton pump genotype of H. pylori was found to be positive for both F-type and P-type ATPases. Yet, their production in terms of enzyme specific activity varied substantially depending on H. pylori strains, ranging over 3-fold. Its main constituent appeared to be the P-type ATPase pool, in contrast to other common bacterial compositions. Interestingly, the F-type ATPase was observed only when intact H. pyloricells were exposed to pH 4.5 or above (37$^{\circ}C$ for 1 h). In contrast, significant amounts of the P-type ATPase still remained after 1 h of cell treatment even at pH below 4.5. By enriching the acidic medium with RPMI(pH 3.0), the P-type ATPase was stabilized, accompained by inactivation of the F-type ATPase. Using H. pylori membrane vesicles, it was found that ammionia-mediated cation flux increased the rate of ATP hydrolysis by the P-type ATPase. Accordingly, these data strongly suggest that the P-type ATPase is involved or functions as an effective regulator for the cation flux across the H. pylori membrane, thereby reducing the risk of excess proton influx.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.708-713
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• 1994

A new flux observer based vector control system of an induction motor is constructed by using an observer in which the commanded stator currents are used to estimate the rotor flux. In this system, the flux observer is formulated by using a model of induction motor in a stationary coordinate system. By considering an observer of induction motor in a fixed co-ordinate system located on its secondary flux, a slip frequency controlled type of vector control system is also proposed. From these control schemes, the relation between the conventional slip frequency controlled type system and the observer based one is clarified. The steady-state error of the developed torque which is caused by the parameter change of induction motor is analyzed and discussed for the selection of observer gains. The poles of the observer error dynamics and those of the observer based vector control system are calculated analytically by neglecting the machine parameter change. In order to analyze the robust stability, a linear model of the observer based vector control system is proposed taking into account the machine parameter change. By using this model, the trajectories of the poles and zeros of the torque transfer function are computed and discussed. To test validity of the theoretical analysis, experiments are conducted by using a digital signal processor (TMS320C30) and a current controlled voltage source PWM inverter.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.7
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• pp.399-405
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• 2002

This paper presents an implementation of digital high-performance Position sensorless motion control system of an induction motor drives with Direct Torque Control(DTC). The system consist of closed loop stator flux and torque observer, speed and torque estimators, two hysteresis controller, optimal switching look-up table, IGBT voltage source inverter, and TMS320C31 DSP board. The stator flux observer is based on the combined current and voltage model with stator flux feedback adaptive control of which inputs are current and voltage sensed on motor terminal for wide speed range. The speed observer is using the model reference adaptive system(MRAS) with rotor flux linkages for speed turning signal. The simulation and experimental results are provided to evacuate the consistency and the performance of the suggested position sensorless control algorithm. The developed position sensorless system are shown a good motion control response characteristic and high performance features using 2.2[kw] general purposed induction motor.

• Journal of The Korean Astronomical Society
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• v.47 no.6
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• pp.201-207
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• 2014

We report the development of solar flux receivers operating at 2.8 GHz to monitor solar radio activity. Radio waves from the sun are amplified, filtered, and then transmitted to a power meter sensor without frequency down-conversion. To measure solar flux, a calibration scheme is designed with a noise source, an ambient load, and a hot load at $100^{\circ}C$. The receiver is attached to a 1.8 m parabolic antenna in Icheon, owned by National Radio Research Agency, and observation is being conducted during day time on a daily basis. We compare the solar fluxes measured for last seven months with solar fluxes obtained by DRAO in Penticton, Canada, and by the Hiraiso solar observatory in Japan, and finally establish equations to convert observed flux to the so-called Penticton flux with an accuracy better than 3.2 sfu.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.9
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• pp.373-380
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• 2016

Spray cooling is a technology of increasing interest for electronic cooling and other high heat flux applications. In this study, heat transfer coefficients (HTCs) and critical heat fluxes (CHFs) are measured on a smooth square flat copper heater of $9.53{\times}9.53mm$ at $36^{\circ}C$ in a pool, a smooth flat surface and Thermoexcel-E surfaces are used to see the change in HTCs and CHFs according to the surface characteristics and FC-72 is used as the working fluid. FC-72 fluid has a significant influence on heat transfer characteristics of the spray over the cooling surface. HTCs are taken from $10kW/m^2$ to critical heat flux for all surfaces. Test results with Thermoexcel-E showed that CHFs of all enhanced surface is greatly improved. It can be said that surface form affects heat transfer coefficient and critical heat flux.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.1
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• pp.18-27
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• 2002

This paper presents an implementation of digital high-performance speed sensorless control system of an induction motor drives with Direct Torque Control(DTC). The system consists of closed loop stator flux and torque observer, speed and torque estimators, two hysteresis controllers, an optimal switching look-up table, IGBT voltage source inverter, and TMS320C31 DSP controller board. The stator flux observer is based on the combined current and voltage model with stator flux feedback adaptive control for wide speed range. The speed estimator is using the model reference adaptive system(MRAS) with rotor flux linkages for speed turning signal estimation. In order to prove the suggested speed sensorless control algorithm, and to obtain a high-dynamic robust adaptive performance, we have some simulations and actual experiments at low(20rpm) and high(1000rpm) speed areas. The developed speed sensorless system are shown a good speed control response characteristic, and high performance features using 2.2[kW] general purposed induction motor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.912-916
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• 2001

Fluxmeter is a measuring instrument the magnetic flux intensity by means of an integration of the voltage induced to a search coil to unit time. It also is required to a precise integrator since the voltage induced to a search coil has a differential value of the flux ${\Phi}$ to unit time. In this study, a bias current which is a main problem of the integrator in a drift troublesome depending on the temperature of a FET is investigated. We have confirmed that the temperature dependence of both the bias current of a integrator using the FET and the reversal saturated current of the minor carrier in a P-N junction of a semiconductor were the same. The property of a commercial integrator goes rapidly down with increasing temperature. The bias current of a FET is increased twice as much with 10$^{\circ}C$ increment. As a result, the low drift integrator could be developed by setting the lower temperature up with a pottier device.