• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.452-455
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• 2008

A new passive control technique of cavity-induced pressure oscillations has been investigated numerically for a supersonic two-dimensional flow over open rectangular cavities at Mach number 1.83 just upstream of a cavity, in which a sub-cavity system is installed on the backward-facing step of the main cavity. A third-order TVD (Total Variation Diminishing) finite difference scheme with MUSCL is used to discretize the spatial derivatives in the unsteady compressible Navier-Stokes equations. The results obtained show that the present sub-cavity system is very effective in reducing cavity-induced pressure oscillations. The results also showed that the resultant amount of attenuation of cavity-induced pressure oscillations was dependent on the length and thickness of the flat plate, and also on the depth of the sub-cavity used as an oscillation suppressor.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.810-815
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• 2003

Flow-induced noise propagated from flow over a sphere is numerically investigated for laminar flow at Re = 300 and 425, and for turbulent flow at Re = 3700 and $10^4$, where the Reynolds number is based on the freestream velocity and the sphere diameter. The numerical method used for obtaining the flow over a sphere is based on an immersed boundary method in a cylindrical coordinate system. The Curle’s solutions of the Lighthill’s acoustic analogy with and without the far-field and compact-source approximation are used in order to investigate the noise field from flow over a sphere. Since the drag and lift forces change irregularly in time at Re = 425, 3700 and $10^{4}$, the noise propagates in a complicated manner. At Re = 300, 425 and $10^{4}$, the noise from dipole sources is much larger than that from quadrupole sources. On the other hand, at Re = 3700, the quadrupole source becomes dominant. The temporal variation of the flow-induced noise around a sphere is obtained at some observation points, which shows that the peak frequency corresponds to the Strouhal number associated with the wake instability.

• Journal of Microbiology
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• v.34 no.3
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• pp.253-269
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• 1996

Infection of fish cells with IHNV resulted in gradual increase in cytosolic free Ca$\^$2+/ concentration ([Ca$\^$2+/)] in CHSE, gradual decrease in [Ca$\^$2+/] in FHM, and no significant change in RTG cells. The degree of [Ca$\^$2+/] increase or decrease was dependent on the amount of infectious virus, and these [Ca$\^$2+/] variations were maximal at 16 hours after virus infection (p. i.) in both cell lines. When the fish cells were infected with inactivated IHNV, evident variation in [Ca$\^$2+/] was not observed. Thus, infectivity of IHNV appears to correlate with changes in [Ca$\^$2+/] in virus-infected cells. These IHNV-induced [Ca$\^$2+/] changes were partially blocked by cycloheximide, but not affected by cordycepin. It seems to be that virus-induced Ca$\^$2+/ variations were more related with protein synthesis than RNA synthesis. Various Ca$\^$2+/ related drugs were used in search for the mechanisms of the [Ca$\^$2+/], changes following IHNV infection of CHSE cells. Decreasing extracellular Ca$\^$2+/ concentration or blocking Ca$\^$2+/ influx from extracellular media inhibited the IHNV-induced increase in [Ca$\^$2+/], in CHSE cells. Similar results were obtained with intracellular Ca$\^$2+/ sources are important in IHNV-induced [Ca$\^$2+/] increase in CHSE cells.

• Smart Structures and Systems
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• v.9 no.2
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• pp.189-206
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• 2012

This paper focuses on the actuation system combined with a piezoelectric transducer and an electric circuit, which leads to a new insight; the electric actuation system is equivalent to mechanical variable-stiffness actuation systems. By controlling the switch in the circuit, the electric status of the piezoelectric transducer is changed, and consequently a variable-stiffness mechanism is achieved on the electric actuator. This proposed actuator features a shift in the equilibrium point of force, while conventional electrically-induced variable-stiffness actuators feature the variation of the stiffness value. We intensively focus on the equilibrium shift in the actuation system, which has been neglected. The stiffness of the variable-stiffness actuator is periodically modulated by controlling the switch, to suppress the vibration of the system in an open-loop way. It is proved that this electric actuator is equivalent to its mechanical counterpart, and that the electrical version has some practical advantages over the mechanical one. Furthermore, another kind of electrically-induced variable-stiffness actuator, using an energy-recycling mechanism is also discussed from the viewpoint of open-loop vibration control. Extensive numerical simulations provide comprehensive assessment on both electrically-induced variable-stiffness actuators employed for open-loop vibration control.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.114-122
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• 2024

Irradiation-induced defects and the precipitates in the wrapper material of the Indian Fast Breeder Test Reactor (FBTR), SS 316 are analyzed using the synchrotron source-based Angle Dispersive X-Ray Diffraction (ADXRD) technique with X-rays of energy 17.185 keV (wavelength ~0.72146 Å). The differences and similarities in the high displacement damage samples as a function of dpa (displacement per atom) and dpa rate in the range of 2.9 × 10^-7- 9 × 10^-7 dpa/s are studied. Ferrite and M₂₃C₆ are commonly observed in the present set of high displacement damage 40-74 dpa SS 316 samples irradiated at temperatures in the range of 400-483 ℃. Also, the dislocation density has increased as a function of the irradiation dose. The X-ray diffraction peak profile parameters quantified such as peak shift and asymmetry show that the irradiation-induced defects are sensitive to the dpa rate-irradiation temperature combinations. The increase in yield strength as a function of displacement damage is also correlated to the dislocation density.

• Journal of Radiation Protection and Research
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• v.28 no.2
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• pp.117-125
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• 2003

It was reported that radiopharamaceuticals induced radiation adaptive response (RAR) in patients undergoing nuclear medicine imaging studies. Individual variations of RAR were not studied well. The purpose of this study was to evaluate individual variation of RAR in patients undergoing nuclear medicine imaging studies. Peripheral lymphocytes were collected from 23 patients undergoing $^{99m}Tc-diethylenetriamine$ pentaacetic acid $(^{99m}Tc-DTPA)$ renal scintigraphy, 18 patients undergoing $^{99m}Tc-methylene$ diphosphonate $(^{99m}Tc-MDP)$ bone scintigraphy and 21 patients undergoing $^{99m}Tc-tetrofosmin\;(^{99m}Tc-TF)$ scintigraphy were collected before and 4 hours after injection of radiopharmaceuticals. The lymphocytes were exposed to challenge dose of 2 Gy gamma rays using a cell irradiator. Numbers of ring-form (R) and dicentric (D) chromosomes were counted under the light microscope. and used to calculate the frequency of chromosomal aberration [Ydr=(D+R)/total number of counted lymphocytes]. Adaptation index (k) was defined 3s ratio of Ydr in conditioned lymphocytes over Ydr in unconditioned lymphocytes. Coefficients of variance of k in $^{99m}Tc-DTPA,\;^{99m}Tc-MDP\;and\;^{99m}Tc-TF$ were 35%, 34% and 21%, respectively k was not dependent upon age, sex, and underlying diseases. There was a wide variation of RAR induced by radiopharmaceuticals among patients undergoing nuclear medicine procedures. It remains to be determined for causes of such variation.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.57-63
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• 2016

Thermally induced phase separation (TIPS) and nonsolvent induced phase separation (NIPS) were simultaneously induced for the preparation of flat PVDF membranes. N-methyl-2-pyrrolidone (NMP) was used as a solvent and dibutyl-phthlate (DBP) was used as a diluent for PVDF. When PVDF was melt blended with NMP and DBP, crystallization temperature was lowered for TIPS and unstable region was expanded for NIPS. Ratio of solvent to diluent changed the phase separation mechanism to obtain the various membrane structures. Contact mode of dope solution with nonsolvent determined the dominant phase separation behavior. Since heat transfer rate was greater than mass transfer rate, surface structure was formed by NIPS and inner structure was by TIPS. Quenching temperature of dope solution also affected the phase separation mechanism and phase separation rate to result in the variation of structure.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.555-561
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• 2005

This experimental study was executed to obtain basic data for actual engine operation using radical induced ignition method (RI) which can achieve emission reduction and high efficiency due to the rapid bulk combustion. In this study, a direct injection diesel engine was converted into SI type engine with a sparkplug. The modified SI type engine can be divided into two classes. One is the SI engine with a sparkplug only at the cylinder head, and the other is the SI engine with the sparkplug which is enveloped in a sub-chamber. Also, a basic experimental was conducted in order to investigate combustion mechanism of radical induced injection before the experiment execution for actual engine using the modified SI engine. The bulk combustion phenomenon of radical induced ignition method was analyzed from the basic experiment by using a constant volume chamber. Volume value of sub-chamber used in this experiment is approximately $0.2\%$ of one of the main combustion chamber. In this paper, combustion characteristics using radical induced injection method was compared with that of using spark ignition method according to change in the engine speed and equivalence ratio. As a result, in the case of the radical induced injection engine, the combustion duration and cycle variation were respectively reduced ranged from $\Phi$(equivalence ratio)=0.8 (lean mixture ratio) to $\Phi$=1.0 (stoichiometric ratio).

• Journal of Astronomy and Space Sciences
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• v.30 no.3
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• pp.179-185
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• 2013

Photometric observation is one of the most effective techniques for determining the physical characteristics of unknown space objects and space debris. In this research, we examine the change in brightness of the Communication, Ocean, Meteorological Satellite-1 (COMS-1) Geostationary Orbit Satellite (GEO), and compare it to our estimate model. First, we calculate the maximum brightness time using our calculation method and then derive the light curve shape using our rendering model. The maximum brightness is then calculated using the induced equation from Pogson's formula. For a comparison with our estimation, we carried out photometric observation using an optical telescope. The variation in brightness and the shape of the light curve are similar to the calculations achieved using our model, but the maximum brightness shows a slightly different value from our calculation result depending on the input parameters. This paper examines the photometric phenomenon of the variation in brightness of a GEO satellite, and the implementation of our approach to understanding the characteristics of space objects.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.116-119
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• 2015

Field-effect transistor (FET)-based ion or biosensors have been intensively studied so far. Among many measurement methods, the variation of the drain current can be induced when ions or biomolecules are interacted with sensing membranes located on the gate insulator of FET. One of typical FET-type sensors is an ion-sensitive field-effect transistor (ISFET) utilized in this study. In ISFET, the voltage is usually applied to the reference electrode instead of the gate voltage. Firstly, the voltage applied to the reference electrode versus the drain current was observed, and the steepest slope in this graph was found. Using this point, the optimized condition was established for the larger variation of the drain current in the saturated region in response to the variation of the input in the dynamic range.