• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.4
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• pp.47-55
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• 2009

The purpose of this study is to verify the transfer function of input acceleration and output control force by linearizing a velocity-dependent damping term of Liquid Column Vibration Absorber (LCVA). Analytical and experimental research is conducted to identify natural frequency, damping ratio and participated mass ratio of LCVA with various section ratios of vertical and horizontal areas. Findings obtained experimentally by the shaking table test are compared with analytical findings using optimization technique with constraints. The results indicate that the level of liquid and section ratio of LCVA affect the characteristics of damping ratio and mass ratio. Damping and mass ratio increase as the section of vertical column of LCVA decreases, due to turbulence in the elbow of LCVA.

• Clean Technology
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• v.18 no.4
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• pp.331-340
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• 2012

Synthetic methods of colloids have been significantly developed in industry due to their significant demand for preparation of functional particles. Recently, dynamic/static microfluidic system has emerged as a promising route to the synthesis of the particles, providing precise control of physical and chemical properties such as size, shape, porosity, surface roughness, and surface functionality. These formed particles can be potentially used in various applications including medical diagnostics, photonic device, and biological industry. In addition, these particles provide a novel route to create new materials via their directed self-assembly, and it enable to study and predict the natural phenomenon by mimicking of the nature. Therefore, we describe recent progress for functional colloid particles and its applications.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.380-384
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• 2004

A fuel spiking test was performed to measure the surge margin of the compressor in a gas turbine engine. During the test, fuel spiking signal was superimposed on the engine controller demand and the mixed signals were used to control a fuel line servo-valve. For the superimposition, a subsystem composed of a fuel controller and a function generator was used. During the fuel spiking test, the original scheduled fuel signals and the modified signals were compared to guarantee the consistency excluding the spiking signals. The spiking signals were carefully selected to maintain the engine speed constant. The fuel spiking effects were checked by three dynamic pressure sensors. Sensors were placed before the servo-valve, after the servo-valve, and after the compressor location, respectively. The modulations of the spiking signal duration and fuel flow rate were examined to make the- operating point approach the surge region. The real engine test was performed at the Altitude Engine Test Facility (AETF) in Korea Aerospace Research Institute (KARI). In the real engine test, fuel spiking signals with 25~50 ㎳ of spiking signal time and 17~46 % of base fuel flow rate condition were used. The dithering signal was 5~6 ㎃ at 490 Hz. The test results showed good agreement between the fuel spiking signals and the fuel line pressure signals. Also, the compressor discharge pressure signals showed fuel spiking effects and the changes of the operating point on the compressor characteristic map could be traced.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.2
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• pp.19-28
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• 2010

Generally, combustion instability is generated by the mutual coupling between the heat release and the acoustic pressure in the combustor. On the occasion, the acoustic pressure generates the oscillation of the mass flow rate of propellant injected from injector, and this oscillation again affects combustion in the combustor. So, the dynamic characteristics of the injector have been studied to control combustion instability using injector itself in Russia from 1970's. In order to study injector dynamics, a mechanical pulsator for forced pressure pulsation is produced and the method to quantify the mass flow rate of the propellant that is oscillating at the exit of the injector is developed. With the pulsator and the method, pulsating values of the mass flow rate, pressure, liquid film thickness, and axial velocity generated at the exit of the simplex swirl injector are measured in real time. And phase-amplitude characteristics of each parameter are analyzed using these pulsating values acquired at the exit of the simplex swirl injector.

• Smart Structures and Systems
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• v.18 no.2
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• pp.355-374
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• 2016

This paper presents and compares a one-dimensional (1D) bending theory for piezoelectric thin beam-type structures with resistive-inductive electrodes to ANSYS$^{(R)}$ three-dimensional (3D) finite element (FE) analysis. In particular, the lateral deflections and vibrations of slender piezoelectric beams are considered. The peculiarity of the piezoelectric beam model is the modeling of electrodes in such a manner that is does not fulfill the equipotential area condition. The case of ideal, perfectly conductive electrodes is a special case of our 1D model. Two-coupled partial differential equations are obtained for the lateral deflection and for the voltage distribution along the electrodes: the first one is an extended Bernoulli-Euler beam equation (second-order in time, forth order in space) and the second one the so-called Telegrapher's equation (second-order in time and space). Analytical results of our theory are validated by 3D electromechanically coupled FE simulations with ANSYS$^{(R)}$. A clamped-hinged beam is considered with various types of electrodes for the piezoelectric layers, which can be either resistive and/or inductive. A natural frequency analysis as well as quasi-static and dynamic simulations are performed. A good agreement between the extended beam theory and the FE results is found. Finally, the practical relevance of this type of electrodes is shown. It is found that the damping capability of properly tuned resistive or resistive-inductive electrodes exceeds the damping performance of beams, where the electrodes are simply linked to an optimized impedance.

• Journal of Ginseng Research
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• v.41 no.3
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• pp.361-369
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• 2017

Background: The chemical constituents of Panax ginseng are changed by processing methods such as steaming or sun drying. In the present study, the chemical change of Panax ginseng induced by steaming was monitored in situ. Methods: Samples were separated from the same ginseng root by incision during the steaming process, for in situ monitoring. Sampling was sequentially performed in three stages; FG (fresh ginseng) ${\rightarrow}$ SG (steamed ginseng) ${\rightarrow}$ RG (red ginseng) and 60 samples were prepared and freeze dried. The samples were then analyzed to determine 43 constituents among three stages of P. ginseng. Results: The results showed that six malonyl-ginsenoside (Rg1, Rb1, Rb3, Rc, Rd, Rb2) and 15 amino acids were decreased in concentration during the steaming process. In contrast, ginsenoside-Rh1, 20(S)-Rg2, 20(S, R)-Rg3 and Maillard reaction product such as AF (arginine-fructose), AFG (arginine-fructose-glucose), and maltol were newly generated or their concentrations were increased. Conclusion: This study elucidates the dynamic changes in the chemical components of P. ginseng when the steaming process was induced. These results are thought to be helpful for quality control and standardization of herbal drugs using P. ginseng and they also provide a scientific basis for pharmacological research of processed ginseng (Red ginseng).

• Journal of the Korean Solar Energy Society
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• v.37 no.3
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• pp.47-59
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• 2017

As the global warming threats to humanity, renewable energy is considered the key solution to overcome the climate change. In this circumstance, distributed PV systems are being expanded significantly its market share in the renewable energy industry. The performance of inverter is the most important component at PV system and numerous researches are focusing on it. In order to improve the inverter, PV simulator is an essential device to experiment under various load and conditions. This paper proposes the PV Power-Hardware-In-Loop simulator (PHILS) with real-time processing converted electrical and mathematical models to improve computation speed. Single-diode PV model is used in MATLAB/SIMULINK for the PV PHILS to boosting computation speed and dynamic model accuracy. In addition, control algorithms for sub-components such as DC amplifier, measurement device and several interface functions are implemented in the model. The proposed PV PHILS is validated by means of experiments with commercial PV module parameters.

• STI Policy Review
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• v.3 no.1
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• pp.46-62
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• 2012

This study investigates the effects of the two most important indicators of a nation's state of scientific infrastructure: R&D investment and the number of R&D researchers engaged in high-tech product export competitiveness for a panel of 11 countries/economies from East Asia from 1994 to 2010. A GMM panel estimation method was employed to account for the dynamic effect of trade and to control for un-observed country specific effects that may arise due to an inter-country differences and intra-country dynamics. Accordingly, the empirical results reveal that (once controlled for the influence of per capita income) physical capital and infrastructure, a 1% increase in a country's expenditure on the ratio of R&D to GDP may increase high-tech product export performance by approximately $397 million per year. Other factors constant, a 1% increase in the number of R&D researchers is expected to increase the ability to export high-tech products by approximately $67 million. The East Asian development experience demonstrates how latecomers can follow systematic industrialization and join the handful of economies that have come a long way toward closing the knowledge gap with the global technological leaders. However, this does not mean that the policy approaches and overall commitments pursued by each East Asian economy in relation to R&D investment and acquisition of an adequate pool of researchers, and their ultimate achievements in high-tech product export competitiveness were uniform. As a result, there is still a significant variation among countries/economies in terms of performance. This study recommended a number of potential tools and policy instruments that may assist policy makers to foster R&D as an engine to enhance the high-tech product export competitiveness.

• Journal of Korea Society of Industrial Information Systems
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• v.5 no.2
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• pp.22-31
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• 2000

The VB5.2 interface of B-lSDN, that is located between an access network and a service node, allows dynamic allocation and release of ATM resources. In this paper, we propose the B-ANCC protocol of the VB5.2 interface to minimize the overall connection setup delay by introducing the access network. The B-ANCC protocol enhances the B-BCC protocol and adopts a parallel interworking function with signaling protocols in the service node. To confirm the correctness of the proposed B-ANCC protocol, we validate it using the automated validation tool, SPIN. We analyze and simulate the sequential interworking model based on the B-BCC protocol and the parallel interworking model based on the B-ANCC protocol, in terms of a connection setup delay and a completion ratio. It is shown that our proposed parallel interworking model with B-ANCC reduces a setup delay and improves a completion ratio compared to the sequential interworking model with B-BCC.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.2
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• pp.109-114
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• 2005

Ion fluxes across the plasma membrane activated by 1 mM $Ce^{4+}$, cell apoptosis and taxol biosynthesis in suspension cultures of Taxus cusp/data were studied. The extracellular pH sharply decreased upon the addition of 1 mM $Ce^{4+}$, then increased gradually and exceeded the initial pH value over a time period of 12 h. The extracellular $Ca^{2+}$ concentration decreased within the first 3 h after the addition of $Ce^{4+}$, then gradually decreased to one third of initial value in control at about 72 h and remained unchanged afterwards. Experiments with an ion channel blocker and a $Ca^{2+}$-channel blocker indicated that the dynamic changes in extracellular pH and the $Ca^{2+}$ concentration resulted from the $Ce^{4+}$-induced activation of W uptake and $Ca^{2+}$ influx across the plasma membrane via ion channels. A pretreatment of the ion channel blocker initiated $Ce^{4+}$-treated cells to undergo necrosis, and the prior addition of the $Ca^{2+}$-channel blocker inhibited $Ce^{4+}$-induced taxol biosynthesis and apoptosis. It is thus inferred that W uptake is necessary for cells to survive a $Ce^{4+}$-caused acidic environment and is one of the mechanisms of $Ce^{4+}$-induced apoptosis. Furthermore, the $Ca^{2+}$ influx across the plasma membrane mediated both the $Ce^{4+}$-induced apoptosis and taxol biosynthesis.