• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.35.2-35.2
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• 2015

We present the results of simultaneous observations of the H2O and SiO masers emitted from the circumstellar envelopes (CSEs) of the late-type stars. These observations have been carried out at the four frequency bands (K, Q, W and D bands) using KVN to apply the source frequency phase referencing (SFPR) analysis to the maser lines. We obtain the relative positions between the H2O and the SiO maser spots by using the SFPR method, which are very important to study the physical links between the inner and the outer parts of the CSEs of the late-type stars. The relative positions between the SiO maser spots of the different transitions are also obtained very accurately, which are very crucial to investigate the pumping mechanism of the SiO maser lines. From our results, the capability of the simultaneous multi-band observation of KVN is proved to be powerful to study the complicated physical environments of the CSEs and the stellar evolution of the late-type stars.

• Journal of Power System Engineering
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• v.21 no.3
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• pp.74-84
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• 2017

This paper presents the development of the underwater cleaning robot platform for a higher efficiency in manufacturing industry. Human operators directly go into the cistern and clean sludge after drainage of the water so far. It is sometimes dangerous because of the harmful chemical materials from the product making process. In addition, it takes long time for water drainage and supplying it back. However, the robot cleaning operation does not need to drain water so that it could be applied to the sludge cleaning work at any time without the plant pause. Moreover, it can prevent the safety accidents because human operators are not necessary to enter directly the sludge cisterns. This paper shows the performance of cleaning work that can be applied in the industrial field through the design and development of underwater cleaning robot platform. And these results demonstrate that the developed underwater cleaning robot has great possibilities to clean other industrial water cisterns.

• Journal of Yeungnam Medical Science
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• v.6 no.2
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• pp.217-222
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• 1989

In this study, high frequency oscillatory ventilator was designed and constructed. Using designed by phase-lock loop system, in order to accurately and easily treat both the outlet volume and rpm. A system has been designed and is being evaluated using CD4046A PLL IC. We use this PLL IC for the purpose of motor controls. The device consists of PLL system, pumping mechanism, piston, cylinder, and special crank shaft are required. This system characteristics were as follows : 1) Frequency : 20-1800rpm. 2) Outlet air volume : 1-50cc.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.3
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• pp.142-145
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• 2013

The upconversion (UC) luminescence of $Li^+/Er^{3+}/Yb^{3+}$ co-doped $CaWO_4$ phosphors and effects of $Yb^{3+}$ concentration are investigated in detail. Single crystallized $CaWO_4$ : $Li^+/Er^{3+}/Yb^{3+}$ phosphor can be obtained, co-doped up to 35.0/5.0/30.0 mol% ($Li^+/Er^{3+}/Yb^{3+}$) by solid-state reaction. Under 980 nm excitation, $CaWO_4$ : $Li^+/Er^{3+}/Yb^{3+}$ phosphor exhibited strong green UC emissions visible to the naked eye at 530 and 550 nm induced by the intra 4f transitions of $Er^{3+}$ ($^4H_{11/2}$, $^4S_{3/2}{\rightarrow}^4I_{15/2}$). The optimum doping concentrations of $Yb^{3+}$ that would result in the highest UC luminescence were determined, and a possible UC mechanism that depends on the pumping power is discussed in detail.

• Corrosion Science and Technology
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• v.16 no.5
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• pp.265-272
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• 2017

Inhibition of pitting corrosion of the copper sprinkler tubes by removing dissolved oxygen in water with sodium sulfite was studied on the wet sprinkler systems operated in 258 household sites. First, air in the sprinkler tubing was removed by vacuum pumping. The tube was then filled with sodium sulfite dissolved in water. Sodium sulfite was very effective in maintaining a very low dissolved oxygen concentration in water in the sprinkler tube for the observation period of six months. Water leakage from the copper sprinkler tube was reduced significantly by using sodium sulfite. Both pitting corrosion process and pitting corrosion inhibition mechanism were investigated by examining microscopical and structural aspects of corrosion pits formed in failed copper sprinkler tube. Pitting corrosion was caused by pressurized air as well as sediments such as sand particles in copper tubes through oxygen concentration cells. It was confirmed microscopically that growth of corrosion pits was stopped by reducing dissolved oxygen concentration to a very level by using sodium sulfite.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1889-1896
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• 2003

In the microfluidic applications, viscous-driven pumping mechanism is a promising one since the viscous effect increases significantly as the size of device decreases, relative to the inertial effect. However, there exist a few drawbacks we have to improve such as low efficiency and small volume flow rate. In the present study, an optimum design synthesis is proposed to enhance the performance characteristics of the micropump with single rotating cylinder. First, the unstructured grid CFD method is described and validated by comparing its results to the previous results. Next, an automated optimum design synthesis tool is constructed by combining the aforementioned CFD analysis model with the mathematical optimization model. This technique is used to improve the performance characteristics of newly designed viscous-driven pump. The presented results show that the fluid dynamic optimization tool is robust and may be applied to other microfluidic device design applications.

• Ocean Systems Engineering
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• v.7 no.2
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• pp.157-177
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• 2017

This research is based on the concept of safety airbag to design a self-rescue system for the autonomous underwater vehicle (AUV) using micro inertial sensing module. To reduce the possibility of losing the underwater vehicle and the difficulty of searching and rescuing, when the AUV self-rescue system (ASRS) detects that the AUV is crashing or encountering a serious collision, it can pump carbon dioxide into the airbag immediately to make the vehicle surface. ASRS consists of 10-DOF sensing module, sensing attitude algorithm and air-pumping mechanism. The attitude sensing modules are a nine-axis micro-inertial sensor and a barometer. The sensing attitude algorithm is designed to estimate failure attitude of AUV properly using sensor calibration and extended Kalman filter (SCEKF), feature extraction and backpropagation network (BPN) classify. SCEKF is proposed to be used subsequently to calibrate and fuse the data from the micro-inertial sensors. Feature extraction and BPN training algorithms for classification are used to determine the activity malfunction of AUV. When the accident of AUV occurred, the ASRS will immediately be initiated; the airbag is soon filled, and the AUV will surface due to the buoyancy. In the future, ASRS will be developed successfully to solve the problems such as the high losing rate and the high difficulty of the rescuing mission of AUV.

• Natural Product Sciences
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• v.21 no.2
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• pp.128-133
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• 2015

Lindera obtusiloba has been widely used as a traditional medicine for the treatment of lots of diseases, including abdominal pain, bruise, and hepatocirrhosis. Here in this study, we elucidated the lifespan-extending effect of methanolic extract of Lindera obtusiloba (MLO) using Caenorhabditis elegans model system. We found that MLO has potent lifespan extension activities under normal culture condition. Then, we determined the protective effects of MLO on the stress conditions such as osmotic, thermal and oxidative stress. To reveal possible mechanism of MLO-mediated lifespan, we further investigated the effect of MLO on the antioxidant enzyme activities and intracellular ROS levels. Our results demonstrated that superoxide dismutase and catalase activities were significantly up-regulated by MLO treatment, resulted in reduced intracellular ROS levels. In this work, we also tested whether MLO-mediated longevity activity was associated with aging-related factors such as food intake and growth. Our data revealed that both of pharyngeal pumping rate and body length were significantly shifted by MLO treatment, indicating these factors were involved in MLO's lifespan-extension effects. Although MLO induces reduction in food intake, the body movement of MLO-fed aged worms was not decreased, compared to untreated control worms, indicating MLO might extend lifespan without affecting healthspan.

• Journal of Microbiology and Biotechnology
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• v.29 no.8
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• pp.1288-1298
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• 2019

Bacterial ATP synthases drive ATP synthesis by a rotary mechanism, and play a vital role in physiology and cell metabolism. Corynebacterium glutamicum is well known as an industrial workhorse for amino acid production, and its ATP synthase operon contains eight structural genes and two adjacent genes, cg1360 and cg1361. So far, the physiological functions of Cg1360 (GenBank CAF19908) and Cg1361 (GenBank CAF19909) remain unclear. Here, we showed that Cg1360 was a hydrophobic protein with four transmembrane helices (TMHs), while no TMH was found in Cg1361. Deletion of cg1360, but not cg1361, led to significantly reduced cell growth using glucose and acetic acid as carbon sources, reduced F1 portions in the membrane, reduced ATP-driven proton-pumping activity and ATPase activity, suggesting that Cg1360 plays an important role in ATP synthase function. The intracellular ATP concentration in the ${\Delta}cg1360$ mutant was decreased to 72% of the wild type, while the NADH and NADPH levels in the ${\Delta}cg1360$ mutant were increased by 29% and 26%, respectively. However, the ${\Delta}cg1361$ mutant exhibited comparable intracellular ATP, NADH and NADPH levels with the wild-type strain. Moreover, the effect of cg1360 deletion on L-valine production was examined in the L-valine-producing V-10 strain. The final production of L-valine in the $V-10-{\Delta}cg1360$ mutant reached $9.2{\pm}0.3g/l$ in shake flasks, which was 14% higher than that of the V-10 strain. Thus, Cg1360 can be used as an effective engineering target by altering energy metabolism for the enhancement of amino acid production in C. glutamicum.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.519-519
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• 2023

Estuarine dams are a recent and global phenomenon. While estuarine dams can provide the benefit of improved freshwater resources, they can also alter estuarine processes. Due to the wide range of estuarine types and estuarine dam configurations, the effect of estuarine dams on estuaries is not well understood in general. To develop a systematic understanding of the effect of estuarine dam location and freshwater discharge interval on a range of estuarine types (strongly stratified, partially mixed, periodically stratified, and well-mixed), this study used a coupled hydrodynamic-sediment dynamic numerical model (COAWST) and compared flow, sediment transport, and morphological conditions in the pre- and post-dam estuaries. For each estuarine type, scenarios with dam locations at 20, 55 and 90 km from the mouth and discharge intervals of a discharge every 0.5, 3, and 7 days were investigated. The results were analyzed in terms of change in tide, river discharge, estuarine classification, and sediment flux mechanism. The estuarine dam location primarily affected the tide-dominated estuaries, and the resonance length was an important length scale affecting the tidal currents and Stokes return flow. When the location was less than the resonance length, the tidal currents and Stokes return flow were most reduced due to the loss of tidal prism, the dead-end channel, and the shift from mixed to standing tides. The discharge interval primarily affected the river-dominated estuaries, and the tidal cycle period was an important time scale. When the interval was greater than the tidal cycle period, notable seaward discharge pulses and freshwater fronts occurred. Dams located near the mouth with large discharge interval differed the most from their pre-dam condition based on the estuarine classification. Greater discharge intervals, associated with large discharge magnitudes, resulted in scour and seaward sediment flux in the river-dominated estuaries, and the dam located near the resonance length resulted in the greatest landward tidal pumping sediment flux and deposition in the tide-dominated estuaries.