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Analysis of Voltage Noises for the Reliability Improvement of the KSTAR CS Quench Detection
Baek, Geonwoo,Kim, Jinsub,Kang, Hyoungku,Ko, Tae Kuk,Chu, Yong Institute of Electrical and Electronics Engineers 2018 IEEE transactions on applied superconductivity Vol.28 No.4
<P>In the Korea Superconducting Tokamak Advanced Research (KSTAR), quench detection system using central difference averaging (CDA) and mutual inductance compensation (MIK) for central solenoid (CS) magnet has been studied. Similar to the cowound voltage taps, it is expected that this method can provide the good capability of rejecting inductive voltage noise. Accordingly, CDA and MIK method could be considered as a promising way. For this method to be an effective way, the inductive voltages should be accurately estimated, and then the measured CDA voltages are compared with the estimated ones. In previous studies, CS and poloidal field (PF) coils were modeled as the ideal solenoids to calculate mutual inductances between them. However, the nonlinearity of inductances due to Incoloy-908 jackets of PF1–PF5 coils that are ferromagnetic materials still needs to be compensated for more accurate estimation of inductive voltages. In this paper, the inductive voltages were estimated by considering the ferromagnetic effect of Incoloy-908 jackets to compensate the error voltages. Based on this study, the effect of Incoloy-908 on accuracy and reliability of CDA and MIK quench detection scheme was analyzed and discussed.</P>
Field gradient calculation of HTS double-pancake coils considering the slanted turns and the splice
Baek, Geonwoo,Kim, Jinsub,Lee, Woo Seung,Song, Seunghyun,Lee, Onyou,Kang, Hyoungku,Ko, Tae Kuk The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.1
To obtain Nuclear Magnetic Resonance (NMR) measurement of membrane protein, an NMR magnet is required to generate high intensity, homogeneity, and stability of field. A High-Temperature Superconducting (HTS) magnet is a promising alternative to a conventional Low-Temperature Superconducting (LTS) NMR magnet for high field, current density, and stability margin. Conventionally, an HTS coil has been wound by several winding techniques such as Single-Pancake (SP), Double-Pancake (DP), and layer-wound. The DP winding technique has been frequently used for a large magnet because long HTS wire is generally difficult to manufacture, and maintenance of magnet is convenient. However, magnetic field generated by the slanted turns and the splice leads to field inhomogeneity in Diameter of Spherical Volume (DSV). The field inhomogeneity degrades performance of NMR spectrometer and thus effect of the slanted turns and the splice should be analyzed. In this paper, field gradient of HTS double-pancake coils considering the slanted turns and the splice was calculated using Biot-Savart law and numerical integration. The calculation results showed that magnetic field produced by the slanted turns and the splice caused significant inhomogeneity of field.
차로 구분이 가능한 정밀전자지도의 성능 요구사항에 관한 연구
강우용(Wooyong Kang),이은성(Eunsung Lee),이건우(Geonwoo Lee),박재익(Jae-Ik Park),최광식(Kwangsik Choi),허문범(Moonbeom Heo) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.1
To enable the efficient operation of ITS, it is necessary to collect location data for vehicles on the road. In the case of futuristic transportation systems like ubiquitous transportation and smart highway, a method of data collection that is advanced enough to incorporate road lane recognition is required. To meet this requirement, technology based on radio frequency identification (RFID) has been researched. However, RFID may fail to yield accurate location information during high-speed driving because of the time required for communication between the tag and the reader. Moreover, installing tags across all roads necessarily incurs an enormous cost. One cost-saving alternative currently being researched is to utilize GNSS (global navigation satellite system) carrierbased location information where available. For lane recognition using GNSS, a precise digital map for determining vehicle position by lane is needed in addition to the carrier-based GNSS location data. A “precise digital map” is a map containing the location information of each road lane to enable lane recognition. At present, precise digital maps are being created for lane recognition experiments by measuring the lanes in the test area. However, such work is being carried out through comparison with vehicle driving information, without definitions being established for detailed performance specifications. Therefore, this study analyzes the performance requirements of a precise digital map capable of lane recognition based on the accuracy of GNSS location information and the accuracy of the precise digital map. To analyze the performance of the precise digital map, simulations are carried out. The results show that to have high performance of this system, we need under 0.5m accuracy of the precise digital map.
Kim, Suyong,Dangol, Manita,Kang, Geonwoo,Lahiji, Shayan F.,Yang, Huisuk,Jang, Mingyu,Ma, Yonghao,Li, Chengguo,Lee, Sang Gon,Kim, Chang Hyun,Choi, Young Wook,Kim, So Jeong,Ryu, Ja Hyun,Baek, Ji Hwoon,K American Chemical Society 2017 Molecular Pharmaceutics Vol.14 No.6
<P>Dissolving microneedle (DMN), a transdermal drug delivery system in which drugs are encapsulated in a biodegradable polymeric microstructure, is designed to dissolve after skin penetration and release the encapsulated drugs into the body. However, because of limited loading capacity of drugs within microsized structures, only a small dosage can be delivered, which is often insufficient for patients. We propose a novel DMN application that combines topical and DMN application simultaneously to improve skin permeation efficiency. Drugs in pretreated topical formulation and encapsulated drugs in DMN patch are delivered into the skin through microchannels created by DMN application, thus greatly increasing the delivered dose. We used 4-n-butylresorcinol to treat human hyper pigmentation and found that sequential application of serum formulation and DMNs was successful. In skin distribution experiments using Alexa Fluor 488 and 568 dyes as model drugs, we confirmed that the pretreated serum formulation was delivered into the skin through microchannels created by the DMNs. In vitro skin permeation and retention experiments confirmed that this novel combined application delivered more 4-n-butylresorcinol into the skin than traditional DMN-only and serum-only applications. Moreover, this combined application showed a higher efficacy in reducing patients' melanin index and hyperpigmented regions compared with the serum-only application. As combined application of DMNs on serum-treated skin can overcome both dose limitations and safety concerns, this novel approach can advance developments in transdermal drug delivery.</P>
김유성,Hye Su Min,Jiwoo Shin,남지혜,Geonwoo Kang,Jeeho Sim,양휘석,정형일 한국생체재료학회 2022 생체재료학회지 Vol.26 No.4
Background: Dissolving microneedle (DMN) is a transdermal drug delivery system that creates pore in the skin and directly deliver drug through the pore channel. DMN is considered as one of the promising system alternatives to injection because it is minimally invasive and free from needle-related issues. However, traditional DMN patch system has limitations of incomplete insertion and need of complex external devices. Here, we designed film-trigger applicator (FTA) system that successfully delivered DMN inside the skin layers using fracture energy of carboxymethyl cellulose (CMC) film via micropillars. We highlighted advantages of FTA system in DMN delivery compared with DMN patch, including that the film itself can act as DMN applicator. Methods: FTA system consists of DMNs fabricated on the CMC film, DMN array holder having holes aligned to DMN array, and micropillars prepared using general purpose polystyrene. We analyzed punching force on the film by micropillars until the film puncture point at different CMC film concentrations and micropillar diameters. We also compared drug delivery efficiency using rhodamine B fluorescence diffusion and skin penetration using optical coherence tomography (OCT) of FTA with those of conventional DMN patch. In vivo experiments were conducted to evaluate DMN delivery efficiency using C57BL/6 mice and insulin as a model drug. Results: FTA system showed enhanced delivery efficiency compared with that of the existing DMN patch system. We concluded CMC film as a successful DMN applicator as it showed enhanced DMN penetration in OCT and rhodamine B diffusion studies. Further, we applied FTA on shaved mouse dorsal skin and observed successful skin penetration. The FTA group showed higher level of plasma insulin in vivo than that of the DMN patch group. Conclusions: FTA system consisting of simple polymer film and micropillars showed enhanced DMN delivery than that of the existing DMN patch system. Because FTA works with simple finger force without sticky patch and external devices, FTA is a novel and promising platform to overcome the limitations of conventional microneedle patch delivery system; we suggest FTA as a next generation applicator for microneedle application in the future.
Lee, Jeyull,Kim, Junseong,Baek, Geonwoo,Choi, Yojong,Choi, Yoon Hyuck,Zhang, Zhan,Chung, Yoon Do,Kang, Hyoungku,Lee, Haigun,Lee, Sangjin,Ko, Tae Kuk IEEE 2018 IEEE transactions on applied superconductivity Vol.28 No.3
<P>High-temperature superconductors (HTSs) have a much larger thermal margin than low-temperature superconductors, owing to their high critical temperatures. This characteristic allows HTS magnets to tolerate extremely high heat loads that may arise from radiation. Therefore, research on the development of HTS quadrupole magnets is progressing widely. Quadrupole magnets are commonly used for focusing the transported beams of particles in accelerators. In order to focus the beam, the quadrupole magnet uses an iron yoke with a hyperbolic contour. However, the iron yoke induces nonlinear magnetic characteristics because of saturation. Therefore, an air-core HTS quadrupole magnet is proposed to improve the magnetic characteristics. In this paper, we design air-core and iron-core HTS quadrupole magnet models using a harmonic matching method. The field gradient and effective length of both magnets are 12.1 T/m and 550 mm, respectively. In order to verify the performances of the proposed air-core quadrupole magnet, the magnetic field gradient, field uniformity, and effective length are analyzed for operating currents ranging from 50 to 400 A.</P>
Huh, Inyoung,Kim, Suyong,Yang, Huisuk,Jang, Mingyu,Kang, Geonwoo,Jung, Hyungil Elsevier 2018 European journal of pharmaceutical sciences Vol.114 No.-
<P><B>Abstract</B></P> <P>Dissolving microneedle (DMN) is an attractive, minimally invasive transdermal drug delivery technology. The drugs encapsulated in the DMNs are exposed to a series of thermal, chemical, and physical stresses during the fabrication process, decreasing their therapeutic activity. Current DMN fabrication methods, such as micro-molding, drawing lithography, droplet-born air blowing, and centrifugal lithography, undergo different manufacturing processes involving differing stress conditions. Among the methods, we compared the effects of two droplet-based methods, droplet-born air blowing and centrifugal lithography, on the activity of encapsulated drugs using epidermal growth factor and ascorbic acid as model drugs. Although the appearance and physical properties of DMNs fabricated by the two methods were similar, the immunoreactivity of encapsulated epidermal growth factor in centrifugal lithography and droplet-born air blowing was 92.08±2.86% and 80.67±8.00%, respectively, at baseline, and decreased to 75.32±19.40% and 41.75±16.17%, respectively, 24h after drug-loading. The free-radical scavenging activity of ascorbic acid was maintained at 88.24±0.78% in DMNs fabricated by centrifugal lithography, but decreased over time to 67.02±1.11% in DMNs fabricated by droplet-born air blowing. These findings indicate that the manufacturing conditions of centrifugal lithography exert less stress on the drug-loaded DMNs, minimizing activity loss over time, and therefore that centrifugal lithography is suitable for fabricating DMNs loaded with fragile biological drugs.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Han, Seunghak,Nam, Seokho,Lee, Jeyull,Song, Seunghyun,Jeon, Haeryong,Baek, Geonwoo,Kang, Hyoungku,Ko, Tae Kuk The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.3
Current lead is a device that connects the power supply and superconducting magnets. High temperature superconductor (HTS) has lower thermal conductivity and higher current density than normal metal. For these reasons, the heat load can be reduced by replacing the normal metal of the current lead with the HTS. Conventional HTS current lead has same cross-sectional area in the axial direction. However, this is over-designed at the cold-end (4.2 K) in terms of current. The heat load can be reduced by reducing this part because the heat load is proportional to the cross-sectional area. Therefore, in this paper, heat load was calculated from the heat diffusion equation of HTS current leads with uniform and non-uniform cross-sectional areas. The cross-sectional area of the warm-end (65K) is designed considering burnout time when cooling system failure occurs. In cold-end, Joule heat and heat load due to current conduction occurs at the same time, so the cross-sectional area where the sum of the two heat is minimum is obtained. As a result of simulation, current leads for KSTAR TF coils with uniform and non-uniform cross-sectional areas were designed, and it was confirmed that the non-uniform cross-sectional areas could further reduce the heat load.