• Korean Journal of Food Science and Technology
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• v.35 no.1
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• pp.155-158
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• 2003

Time-dependent flow properties of mustard pastes were measured at various total solid contents $(TS,\;18{\sim}30%)$ and shear rates $(15{\sim}25\;s^{-1})$ using a Haake concentric cylinderical viscometer. Experimental data of the stress decay with time of shearing were fitted to three mathematical models proposed by Weltman, Figoni and Shoemaker, and Hahn. Time-dependent flow behaviour of mustard paste increased with increase in TS, but was found to vary in the range of shear rate investigated. Time-dependent model of Weltman was found to be most applicable $(average\;R^2=0.96)$ for mustard paste. Shear stresses for structure breakdown increased with increase in TS, while the structure breakdown rate decreased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.6
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• pp.573-576
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• 2009

We present a passive flow-rate regulator, capable to compensate inlet pressure variation and to maintain a constant flow-rate for precise liquid control. Deflection of the parallel membrane valves in the passive flowrate regulator adjusts fluidic resistance according to inlet fluid pressure without any external energy. Compared to previous passive flow-rate regulators, the present device achieves precision flow regulation functions at the lower threshold compensation pressure of 20kPa with the simpler structure. In the experimental study, the fabricated device achieves the constant flow-rate of $6.09{\pm}0.32{\mu}l/s$ over the inlet pressure range of $20{\sim}50$ kPa. The present flow-rate regulator having simple structure and lower compensation pressure level demonstrates potentials for use in integrated micropump systems.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.717-724
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• 2003

A newly isolated Citrobacter sp. Y19 catalyzes the CO-dependent $H_2$ production (biological water-gas shift reaction) by the actions of CO dehydrogenase (CODH) and hydrogenase. Y 19 requires $O_2$ for fast growth, but its $H_2$ production activity is significantly inhibited by $O_2$. In the present study, the effect of $O_2$ on the activities of CODH ard hydrogenase was investigated quantitatively in both whole cells and broken cells, based on CO-dependent or methyl viologen (MV)-dependent $H_2$ production in addition to CO-dependent MV reduction. In crude cell extracts, CODH activity was mostly found in the soluble fraction. Inactivation of CODH and hydrogenase activities by $O_2$ followed the first-order decay kinetics, and the dependence of the rate constants on $O_2$ partial pressure could be expressed by the Michaelis-Menten equation. In whole cells, the maximum deactivation rate constants ($k_{d,max}$ of hydrogenase and CODH were quite similar: $0.07{\pm}0.03 min^{-1}\;and\;0.10{\pm}0.04 min^{-1}$, respectively. However, the first-order rate constant ($k_{d,max}/K_s$) of CODH ($0.25\;min^{-1}\;atm^{-1}$) at low $O_2$ partial pressures was about 3-fold higher than that of the hydrogenase, since the half-saturation constant ($K_s$) of CODH was about half of that of hydrogenase. In broken cells, both enzymes became significantly more sensitive to $O_2$ compared to the unbroken cells, while $k_{d,max}/K_s$ increased 37-fold for hydrogenase and 6.7-fold for CODH. When whole cells were incubated under anaerobic conditions after being exposed to air for 1 h, hydrogenase activity was recovered more than 90% in 2 h suggesting that the deactivation of hydrogenase by $O_2$ was reversible. On the contrary, CODH activity was not recovered once deactivated by $O_2$ and the only way to recover the activity was to synthesize new CODH. This study indicates that $O_2$ sensitivity of $H_2$ production activity of Citrobacter sp. Y19 is an important drawback as in other $H_2-producing$ bactria.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.295-302
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• 2016

Underwater acoustic communication channel is often defined as a multipath fading channel since the multipath arrivals from various paths interfere with each other and cause frequency dependent constructive or destructive interference in received signals. Therefore signal-to-noise ratio (SNR) of received signal fluctuates as a function of frequency. In addition, sea surface fluctuation induces frequency dependent time variant signal fading due to coherent component variation of surface bounce path. The frequency shift keying (FSK) system is known to be less sensitive and more robust under these interference and fading, and M-ary frequency shift keying (MFSK) system is adopted to increase a data rate. In this study, a bit error rate (BER) of 4 channels 4FSK system are examined in shallow sea multipath channel. Experimental results show that RS code reduces efficiently the BER of 4FSK system since frequency dependent time-varying fading is characterized to give burst errors. The BER of a different data rate or different source-to-receiver range depends on not only the channel coherent bandwidth but also frequency dependent multipath fading.

• The Korean Journal of Physiology
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• v.27 no.1
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• pp.57-66
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• 1993

Effects of a voltage dependent calcium channel antagonist, nifedipine, on the responses of blood pressure, and secretion of atrial natriuretic peptide (ANP) and aldosterone to angiotensin II (Ang II) were compared in male Wistar and spontaneously hypertensive rats (SHR). A low, control or high sodium diet (2, 10 or 25 mmol Na/100 g diet) was fed for 6 weeks from the age of 6 weeks. On the morning of the experiment catheters were inserted under ether anesthesia in the femoral artery for pressure recording and blood sampling, and in the femoral vein for drug infusion. Ang II was infused at a rate of 250 ng/kg/min for 20 min. Nifedipine mixed with Ang II was infused at a rate of $16{\mu}g/kg/min$ for 20 min. Arterial blood samples were collected before and after infusion of Ang II with or without nifedipine. The control plasma level of aldosterone was inversely related to the amount of salt intake, whereas the plasma ANP level was not different between the salt groups. SHR showed a higher basal plasma ANP but a lower aldosterone concentration than Wistar rats. Infusion of Ang II produced a significant increase in blood pressure and plasma levels of aldosterone and ANP: The % increase was not significantly different either between the salt groups or between SHR and Wistar rats. SHR showed a greater pressor response to Ang II but a remarkably smaller decrease in heart rate after Ang II infusion than Wistar rats, With increasing sodium intake, the effect of Ang II on aldosterone secretion was decreased, whereas that on ANP secretion or blood pressure was not changed. Nifedipine decreased the responses of blood pressure and heart rate to Ang II in all groups. Nifedipine caused almost a complete inhibition of Ang II induced ANP secretion, but only a partial inhibition of Ang II induced aldosterone secretion or vasoconstriction. These results indicate that calcium dependent processes were involved in Ang II induced vasoconstriction, and secretions of aldosterone and ANP. However, the calcium dependent process far ANP secretion was considerably different from that for aldosterone secretion or vasoconstriction evoked by ang II. The ang II induced increase in ANP secretion appeared to be caused primarily by activating voltage-dependent calcium channels, whereas Ang II induced aldosterone secretion and vasoconstriction was not.

• Journal of Korean Society for Quality Management
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• v.32 no.3
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• pp.109-125
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• 2004

This paper deals with an optimal process control problem in production of hull structural steel plate with high defective rate. The main quality characteristic(dependent variable) is the internal quality(defect) of plates and is dependent on process parameters(independent variables). The dependent variable(quality characteristics) has three categorical ordinal data and there are 35 independent variables(29 continuous variables and 6 categorical variables). In this paper, we determine the main factors and to develop the mathematical model between internal quality predicted probabilities and the main factors. Secondly, we find out the optimal process condition of main factors through analysis of variance(ANOVA) using simulation. We consider three models to obtain the main factors and the optimal process condition: linear, quadratic, error models.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.361-367
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• 1999

It was observed that the time-dependent sheath which was formed around the planar target biased by negatively voltage pulse with a finite rise time in the plasma source ion implantation. F\Results show that the time-dependent sheath consisted of two parts: the ion matrix sheath development during the pulse rise time and the dynamic sheath motion after attaining the full pulse. The ion matrix sheath development which is in proportion to square root of the pulse time and the pulse rise rate over the plasma density but independent of the ion mass. The dynamic sheath propagates with approximately the ion sound speed.

• Journal of the Korea Computer Industry Society
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• v.2 no.2
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• pp.195-202
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• 2001

In this paper, we show a study on how to model a phoneme of which acoustic feature is changed according to both left-hand and right-hand phonemes. For this purpose, we make a comparative study on two kinds of algorithms; a unit reduction algorithm and decision tree modeling. The unit reduction algorithm uses only statistical information while the decision tree modeling uses statistical information and Korean acoustical information simultaneously. Especially, we focus on how to model context-dependent phonemes based on decision tree modeling. Finally, we show the recognition rate when context-dependent phonemes are obtained by the decision tree modeling.

• Computers and Concrete
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• v.19 no.3
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• pp.305-313
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• 2017

A robust finite element based reinforced concrete bridge deck corrosion initiation model is applied for time-dependent probabilistic sensitivity analysis. The model is focused on uncertainties in the governing parameters that include variation of high performance concrete (HPC) diffusion coefficients, concrete cover depth, surface chloride concentration, holidays in reinforcements, coatings and critical chloride threshold level in several steel reinforcements. The corrosion initiation risk is expressed in the form of probability over intended life span of the bridge deck. Conducted study shows the time-dependent sensitivity analysis to evaluate the significance of governing parameters on chloride ingress rate, various steel reinforcement protection and the corrosion initiation likelihood. Results from this probabilistic analysis provide better insight into the effect of input parameters variation on the estimate of the corrosion initiation risk for the design of concrete structures in harsh chloride environments.

• Archives of Pharmacal Research
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• v.18 no.5
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• pp.314-319
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• 1995

Antacid granules were prepared by agglomeration and powder method in high speed agitation type granulator. The copmositions of the test antacids were sodium bicarbonate nad magnesium carbonate nad a coating material was powder of polyvinylacetal diethyl-aminocacetate (AEA) and an additive material was talc powder. The dissolution characteristics of base from the antacid granules were investigated to evaluate neutralization capacity of hydrochloric profile of base and neutralization behavior, the following results were obtained : The prepared granules showed a pH-dependent dissolution pattern of a base. The dissolution profile of a base was varied with addition of talc powder as well as coating amount of AEA. The relationship between the ratio of dissolution retarded time for 20% and 10% AEA. The relationship between the ratio of dissolution retarded time for 20% AEA coated granules $\theta_{20}/\theta_{10}$ and the diameter reduction of the granules was explained by the rate process of neutralization of hydrochloric acid.