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Search Results: 1 - 10 of 45526 matches for " Jin-Hyuk Kim "
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Power Stabilization System with Counter-Rotating Type Pump-Turbine Unit for Renewable Energy  [PDF]
Toru Miyaji, Risa Kasahara, Toshiaki Kanemoto, Jin-Hyuk Kim, Young-Seok Choi, Toshihiko Umekage
Journal of Power and Energy Engineering (JPEE) , 2014, DOI: 10.4236/jpee.2014.24007
Abstract: Traditional type pumped storage system contributes to adjust the electric power unbalance between day and night, in general. The pump-turbine unit is prepared for the power stabilization system, in this serial research, to provide the constant power with good quality for the grid system, even at the suddenly fluctuating/turbulent output from renewable energies. In the unit, the angular momentum changes through the front impeller/runner must be the same as that through the rear impeller/runner, that is, the axial flow at the outlet should be the same to the axial flow at the inlet. Such flow conditions are advantageous to work at not only the pumping mode but also the turbine mode. This work discusses experimentally the performance of the unit, and verifies that this type unit is very effective to both operating modes.
Isolation and identification of alkaloids and anthocyanins from flower and bulb of Lycoris radiata using HPLC and LC-ESI-MS  [PDF]
Jin-Hyuk Chun, In Hyuk Jang, Mariadhas Valan Arasu, Naif Abdullah Al-Dhabi, Veeramuthu Duraipandiyan, Dong-Hoon Lee, Sanghyun Lee, Sun-Ju Kim
Journal of Agricultural Chemistry and Environment (JACEN) , 2013, DOI: 10.4236/jacen.2013.21004
Abstract: Three anthocyanins (cyanidin 3-diglucoside, cyanidin 3-sambubioside and cyanidin 3-glucoside) together with eleven known alkaloids (lycoricidine, hipppeastrine,O-Demethyllycoramin, lycoricidinol, galanthine, lycorine, lycorenine, lycoramine, galanthamine, homolycorine and pretazettine) were identified in the flower and bulb of Lycoris radiata using high-performance liquid chromatography coupled with UV detection and electrospray ionization mass spectrometry. Anthocyanins play a major role in protecting plant’s DNA from the UV spectrum of sunlight and also in attracting insects for the purpose of pollination. Thus, knowledge on the contents and types of anthocyanins of L. radiata will help to evaluate the adaptive evolution of flowers and provide useful information for the ornamental breeding.
High Temperature Endurable Fiber Optic Accelerometer
Yeon-Gwan Lee,Jin-Hyuk Kim,Chun-Gon Kim
Shock and Vibration , 2014, DOI: 10.1155/2014/571017
Abstract: This paper presents a low frequency fiber optic accelerometer for application in high temperature environments of civil engineering structures. The reflection-based extrinsic fiber optic accelerometer developed in this study consists of a transmissive grating panel, reflective mirror, and two optical fiber collimators as the transceiver whose function can be maintained up to 130°C. The dynamic characteristics of the sensor probe were investigated and the correlation between the natural frequency of the sensor probe and temperature variation was described and discussed. Furthermore, high temperature simulation equipment was designed for the verification test setup of the developed accelerometer for high temperature. This study was limited to consideration of 130°C applied temperature to the proposed fiber optic accelerometer due to an operational temperature limitation of commercial optical fiber collimator. The sinusoidal low frequency accelerations measured from the developed fiber optic accelerometer at 130°C demonstrated good agreement with that of an MEMS accelerometer measured at room temperature. The developed fiber optic accelerometer can be used in frequency ranges below 5.1?Hz up to 130°C with a margin of error that is less than 10% and a high sensitivity of 0.18?(m/s2)/rad. 1. Introduction Over the past three decades, many types of fiber optic accelerometers (FOAs) have been developed because optical fibers (OFs) allow structural health monitoring within highly electromagnetic environments [1].Furthermore, optical fiber with fused silica is useful in a wide temperature range up to about 1000°C [2] although it depends on the optical fiber material such as fused silica and sapphire (Al2O3, single crystal alumina) [3, 4]. While most intensity-based fiber optic sensor systems are relatively low cost, fiber Bragg grating (FBG) sensor systems are rather higher cost wavelength shift interrogation equipment for high speed sampling frequency rates. Alternatively, intensity modulation techniques have been conducted on grating-based extrinsic type fiber optic sensors (FOSs) [5–7] because the grating-based sensors [8, 9] possess significant advantages [10]: simple mechanical structure and good reliability, among others. Therefore, research on grating-based fiber optic sensors has been conducted based on the shutter effect [9, 11] or the Moiré phenomenon techniques [7], which require four optical fiber lines and two grating panels. However, these transmission type FOSs [6, 7, 9, 11], including the Moiré fringe-based FOA, depending on the transmitted light
Measurement of Microvibration by Using Dual-Cavity Fiber Fabry-Perot Interferometer for Structural Health Monitoring
Dae-Hyun Kim,Jin-Hyuk Lee,Byung-Jun Ahn
Shock and Vibration , 2014, DOI: 10.1155/2014/702404
Abstract: Extensive researches have recently been performed to study structural integrity using structural vibration data measured by in-structure sensors. A fiber optic sensor is one of candidates for the in-structure sensors because it is low in cost, light in weight, small in size, resistant to EM interference, long in service life, and so forth. Especially, an interferometric fiber optic sensor is very useful to measure vibrations with high resolution and accuracy. In this paper, a dual-cavity fiber Fabry-Perot interferometer was proposed with a phase-compensating algorithm for measuring micro-vibration. The interferometer has structurally two arbitrary cavities; therefore the initial phase difference between two sinusoidal signals induced from the interferometer was also arbitrary. In order to do signal processing including an arc-tangent method, a random value of the initial phase difference is automatically adjusted to the exact 90 degrees in the phase-compensating algorithm part. For the verification of the performance of the interferometer, a simple vibration-test was performed to measure micro-vibration caused by piezoelectric transducer (PZT). As an experimental result, the interferometer attached on the PZT successfully measured the 50?Hz-vibration of which the absolute displacement oscillated between ?424?nm and +424?nm. 1. Introduction Advanced sensor and structural monitoring technology can play an important role in prioritizing repair and rehabilitation process, improving the cost effectiveness of inspection and maintenance, and ultimately enhancing the longevity and safety of large-scale mechanical systems. Extensive researches have recently been performed to study structural integrity using structural vibration data measured by in-structure sensors [1, 2]. One of the major obstacles preventing sensor-based monitoring is however the unavailability of reliable, easy-to-install, and cost-effective sensors. In particular, civil engineering structures place unique demands on sensors. Besides accuracy, sensors and their cables are expected to be reliable, low in cost, light in weight, small in size, resistant to EM interference, and long in service life. They are required to withstand harsh environments, be moisture-, explosion-, and lightning-proof, and corrosion-resistant. Furthermore, civil structures are usually very large, demanding easy cabling of the sensors. It is very difficult, if not impossible, for the currently available electric-type sensors to satisfy these demanding requirements. Emerging fiber optic sensor technologies have shown
Identification and Determination of Phenolic Compounds in Rapeseed Meals (Brassica napus L.)  [PDF]
Si-Chang Yang, Mariadhas Valan Arasu, Jin-Hyuk Chun, Young-Seok Jang, Yong-Hwa Lee, In Ho Kim, Ki-Taek Lee, Soon-Taek Hong, Sun-Ju Kim
Journal of Agricultural Chemistry and Environment (JACEN) , 2015, DOI: 10.4236/jacen.2015.41002
Abstract: This study aimed in the identification and quantification of phenolic compounds in different four varieties of rapeseeds (Brassica napus L.) using LC-MS and HPLC. LC-MS analysis guided to identify 12 phenolic compounds including sinapine, sinapine(4-O-8')guaiacyl, feruloyl choline(4-O-8') guaiacyl, kaempferol-3-O-sinapoyl-sophoroside-7-O-glucoside, kaempferol-3-O-β-sophoroside, cyclic spermidine-alkaloid, feruloyl choline(5-8')guaiacyl, kaempferol-sinapoyl-trihexoside,1,2-di- O-sinapoyl-gentiobiose, 1,2-di-O-sinapoyl-glucose, feruloyl choline(4-O-8')guaiacyl-di-sinapoyl, and sinapine(4-O-8')guaiacyl-di-sinapoyl, respectively. Total phenolic compounds in rapeseed meals were ranged from 38.50 (2012 “Sunmang”) to 63.95 mg/g dry weight (DW) (2014 Jeju local cultivar). Main phenolic compositions were cyclic spermidine-alkaloid, kaempferol, feruloyl choline, and sinapine. Sinapine was predominant compound among all the samples ranged from 29.74 to 52.24 mg/g DW (mean 79% of total phenolic contents). This study provided the information for the variation of phenolic compounds between the varieties of rapeseeds and the cultivation periods. Furthermore, this information can be developed for bio-energy industry as a reducer of the cost of the bio-energy products.
Effects of Interfacial Charge Depletion in Organic Thin-Film Transistors with Polymeric Dielectrics on Electrical Stability
Jaehoon Park,Jin-Hyuk Bae,Won-Ho Kim,Min-Hoi Kim,Chang-Min Keum,Sin-Doo Lee,Jong Sun Choi
Materials , 2010, DOI: 10.3390/ma3063614
Abstract: We investigated the electrical stabilities of two types of pentacene-based organic thin-film transistors (OTFTs) with two different polymeric dielectrics: polystyrene (PS) and poly(4-vinyl phenol) (PVP), in terms of the interfacial charge depletion. Under a short-term bias stress condition, the OTFT with the PVP layer showed a substantial increase in the drain current and a positive shift of the threshold voltage, while the PS layer case exhibited no change. Furthermore, a significant increase in the off-state current was observed in the OTFT with the PVP layer which has a hydroxyl group. In the presence of the interfacial hydroxyl group in PVP, the holes are not fully depleted during repetitive operation of the OTFT with the PVP layer and a large positive gate voltage in the off-state regime is needed to effectively refresh the electrical characteristics. It is suggested that the depletion-limited holes at the interface, i.e., interfacial charge depletion, between the PVP layer and the pentacene layer play a critical role on the electrical stability during operation of the OTFT.
Output Current Ripple Reduction Algorithms for Home Energy Storage Systems
Jin-Hyuk Park,Hae-Gwang Jeong,Kyo-Beum Lee
Energies , 2013, DOI: 10.3390/en6105552
Abstract: This paper proposes an output current ripple reduction algorithm using a proportional-integral (PI) controller for an energy storage system (ESS). In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of the DC-link voltage. The output current of a DC/DC converter has a ripple component because of the ripple of the DC-link voltage. The second-order harmonic adversely affects the battery lifetime. The proposed algorithm has an advantage of reducing the second-order harmonic of the output current in the variable frequency system. The proposed algorithm is verified from the PSIM simulation and experiment with the 3 kW ESS model.
Specific Radius Change of Quantum Dot inside the Lipid Bilayer by Charge Effect of Lipid Head-Group  [PDF]
Soon Ki Sung, Hyuk Kyu Pak, Jong Hyeok Kwak, Sang Weon Lee, Young Ha Kim, Beong Ik Hur, Seong Jin Jin, Gyeong Rip Kim
Open Journal of Biophysics (OJBIPHY) , 2018, DOI: 10.4236/ojbiphy.2018.83012
Abstract: We studied the quantum dot-liposome complex (QLC), which is the giant unilamellar vesicle with quantum dots (QDs) incorporated in its lipid bilayer. A spin coating method in conjunction with the electroformation technique yielded vesicles with highly homogeneous unilamellar structure. We observed QD size dependence of the QLC formation: QLCs form with blue, green and yellow-emission QD (core radius ~1.05 nm, 1.25 nm and 1.65 nm) but not with red-emission QD (core radius ~2.5 nm). In order to explain this size dependence, we made a simple model explaining the QD size effect on QLC formation in terms of the molecular packing parameter and the lipid conformational change. This model predicts that QDs below a certain critical size (radius ≈ 1.8 nm) can stably reside in a lipid bilayer of 4 - 5 nm in thickness for Egg-PC lipids. This is consistent with our previous experimental results. In the case of red-emission QD, QD-aggregations are only observed on the fluorescent microscopy instead of QLC. We expected that the reduction of packing parameter (P) would lead to the change of specific QD radius. This prediction could be verified by our experimental observation of the shift of the specific QD size by mixing DOPG.
Atypical florid vascular proliferation in appendix: a diagnostic dilemma
Mi Jin Gu, Joon Hyuk Choi, So Hyun Kim
Diagnostic Pathology , 2013, DOI: 10.1186/1746-1596-8-12
Abstract: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1386921325843104 webciteVascular proliferative lesions occurring in the gastrointestinal tract include tumors and tumor-like lesions of the vessels. With the exception of angiodysplasia, vascular abnormalities of the gastrointestinal tract are uncommon [1]. Seven cases of florid vascular proliferations occurring in the intestinal tract have been reported in English literature [1-3]. All reported cases were associated with intussusception or mucosal prolapse and showed microscopic features that overlap with those of angiosarcoma. Florid vascular proliferations are thought to be a secondary response to repeated mucosal trauma and ischemia and differential diagnosis from angiosarcoma is necessary [1]. We herein report on a challenging case showing unusual microscopic findings of the appendix.A 41-year old male presented with melena. He had no other symptoms, such as migratory pain, right lower quadrant abdominal tenderness with guarding, or leukocytosis. Colonoscopy showed non-specific findings, except for adhesioned blood clots in the appendiceal orifice. He underwent laparoscopic appendectomy. No characteristic features were observed on the external surface. Cut sections showed a tiny polypoid mucosa with easy contact bleeding and the appendiceal lumen was filled with blood. Microscopically, inflammatory cells infiltration, diverticulum, parasite, and fecalith were not observed. An exophytic polypoid mass with extensive surface ulceration was observed. The superficial portion of the polyp showed pyogenic granuloma-like features and the deeper portion was composed of vaguely lobulated proliferation of closely packed small capillary-sized vessels and showed infiltrative growth and extension into muscularis propria (Figure 1). Endothelial cells had round to ovoid nuclei and showed minimal nuclear atypia without multi-layering. Mitotic figures were observed infrequently
Jamming transition in a highly dense granular system under vertical vibration
Kipom Kim,Jong Kyun Moon,Jong Jin Park,Hyung Kook Kim,Hyuk Kyu Pak
Physics , 2005, DOI: 10.1103/PhysRevE.72.011302
Abstract: The dynamics of the jamming transition in a three-dimensional granular system under vertical vibration is studied using diffusing-wave spectroscopy. When the maximum acceleration of the external vibration is large, the granular system behaves like a fluid, with the dynamic correlation function G(t) relaxing rapidly. As the acceleration of vibration approaches the gravitational acceleration g, the relaxation of G(t) slows down dramatically, and eventually stops. Thus the system undergoes a phase transition and behaves like a solid. Near the transition point, we find that the structural relaxation shows a stretched exponential behavior. This behavior is analogous to the behavior of supercooled liquids close to the glass transition.
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