• Journal of Magnetics
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• 제15권4호
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• pp.190-193
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• 2010

The design of joints in a transformer core significantly affects the transformer's efficiency. Air gaps cause variations in the flux distribution at the joints of the laminations, which depend on the geometry. Two similar samples consisting of electrical steel strips and amorphous ribbons were made. The spatial flux distributions were determined using an array of search coils for each sample. 2D models of these samples were created and examined by finite element analysis. The magnetic flux distribution for each lamination in the samples was computed. The results show that the flux density in amorphous ribbons above and below the air gap starts to approach saturation at lower flux density levels than for electrical steel. The flux density measured using the search coil under the air gap is increased in amorphous ribbons and decreased in the electrical steel with increasing frequency.

• 한국군사과학기술학회지
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• 제16권4호
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• pp.566-574
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• 2013

In this paper, direct power control system for three-phase PFC AC/DC converter without the source voltage sensors is proposed. The sinusoidal input current and unity effective power factor are realised based on the estimated flux in the observer. Both active and reactive power calculated using estimated flux. The estimation of flux is performed based on the reduced-order virtual flux observer using the actual currents and the command control voltage. Moreover, source voltage sensors are replaced by a estimated flux. DC output voltage has been compensated by DC output ripple voltage estimation algorithm. The active and reactive powers estimation are performed based on the estimated flux and Phase angle. The proposed algorithm is verified through simulation and experiment.

• Journal of Magnetics
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• 제18권1호
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• pp.57-64
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• 2013

Flux linkage of phase windings is a key parameter in determining the behavior of a switched reluctance motor (SRM) [1-8]. Therefore, the accurate prediction of flux linkage at aligned and unaligned rotor positions makes a significant contribution to the design of an SRM and its analytical approach is not straightforward due to nonlinear saturation in flux. Although several different approaches using a finite element analysis (FEA) or a curve-fitting tool have been employed to compute phase flux linkage [2-5], they are not suitable for a simple design procedure because the FEA necessitates a large amount of time in both modeling and solving with complexity for every motor design, and the curve-fitting requires the data of flux linkage from either an experimental test or an FEA simulation. In this paper, phase flux linkage at aligned and unaligned rotor positions is estimated by means of a reluctance network, and the proposed approach is analytically verified in terms of accuracy compared to FEA.

• 천문학회보
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• 제43권2호
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• pp.45.2-45.2
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• 2018

Twisted magnetic flux tubes (also called magnetic flux ropes) are believed to play a crucial role in solar eruptive phenomena. The evolution of a single flux rope with or without the influence of an overlying field of a simple geometry has been extensively studied and its physics is rather well understood. Observations show that interacting flux tubes are often involved in solar eruptions. It was Lau and Finn (1996) who intensively studied the interaction between two flux ropes, whose footpoints are anchored in two parallel planes. In this too simplified setting, the curvature of the flux rope axial fields is totally ignored. In our study, the footpoints of flux ropes are placed in a single plane containing a polarity inversion line as in the real solar active region. Our simulation study is performed for four cases: (1) co-axial field and co-axial current (co-helicity), (2) counter-axial field and co-axial current (counter-helicity), (3) co-axial field and counter-axial current (counter-helicity), and (4) counter-axial field and counter-axial current (co-helicity). Except case 3, each case is found to be related with certain eruptive features.

• 대한기계학회논문집B
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• 제27권2호
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• pp.163-172
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• 2003

Boiling heat transfer coefficients and pressure drops for R-22 and R-407C were measured in horizontal micro-channels. The test section is stainless steel tube, inner tube diameters are 1.8mm and 2.8mm, and the respective lengths are 1500mm and 3000mm. The range of mass flux is 300-600kg/$m^2$s and heat flux is 5-15kW/$m^2$. In this results, pressure drop increased linearly for both R-22 and R-407C with increased mass flux, but the increase of heat flux did not affect the pressure. In addition, the pressure drop was fairly increased in the high quality region rather than low quality region. In the range of low quality, the mass flux had a small affect on the heat transfer coefficients, however, in high quality region, the heat transfer coefficients increased even more with increasing mass flux. Under the low quality region and low mass flux, the heat transfer coefficients increased with increasing heat flux densities. The effects of inner tube diameter were clearly observed. Namely, the measured pressure drop inside inner tube diameter 1.8 mm is higher than 2.8 mm with increasing the mass flux and heat flux. Also, the measured local heat transfer coefficient inside inner tube diameter 1.8 mm is higher than 2.8 mm in the range of high qualities. The experimental data for R-407C compared with proposed correlation using pure refrigerant. The experimental data for R-407C was more decreased than the proposed correlation for pure refrigerant up to 50% or more.

• 한국화재소방학회논문지
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• 제14권2호
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• pp.33-38
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• 2000

전자산업의 공정에서 PCB기판납땜은 괼수적이며 이에 사용하는 Flux내 용제인 IPA(Iso--propyl alcohol)와 메탄올은 인화성과 폭발성이 강한 물질로 화재위험성이 대단히 높다. 또한 메탄올은 유독성물질로 지정되어 있으며, 환경법상 VOC(Volatile Organic Compound : 휘발성유기화합물)규제물질로 지정되어 있어 대체물질 개발이 절실히 요구된다. 이에 기존 Flux특성을 가지고 있으면서 화재위험성은 없고, 휘발성유기화합물 규제물질에는 해당되지 않는 디클로로프로판(Dichloropropane, DCP)를 주성분으로 하여 Flux 특성에 맞는 안정제 및 첨가제를 적정 조성비로 조합하여 용제를 개발하였다. 그 결과 200ppm의 작업환경허용농도를 470 ppm으로 완화시킬 수 있었으며 납땜불량율은 0.083%에서 0%로, 퍼짐성은 85%에서 87%로, 전연저항은 1.0$\times$$10^{12}$$\Omega$에서 6.9$\times$$10^{12}$/$\Omega$으로 기존 Flux보다 우수하였다. 그러므로 Flux의 안정성은 물론 환경안전측면과 품질, 생산성도 향상이 가능함을 확인하였고, 품질 특성시험 및 제품 신뢰성 시험 결과 만족할 만한 곁과를 얻었다.

• Journal of Pharmaceutical Investigation
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• 제29권2호
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• pp.111-115
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• 1999

We have studied the transdermal flux of prostaglandin $E_1$ $(PGE_1)$ from a hydrogel patch through hairless mouse skin, to test the possibility of developing a transdermal delivery system. Karaya gum patch containing $PGE_1$ was prepared by casting method. $PGE_1$ was stable in the patch for 10 weeks. The effect of current application, enhancer (propylene glycol monolaurate : PGML), adhesive and patch thickness on the flux was studied using side-by-side diffusion cell. Passive flux of $PGE_1$ was negligible. Cathodal delivery increased the flux about 20 fold. As the concentrations of PGML increased, flux increased. When 5% PGML was used as the enhancer, maximum flux by cathodal iontophoresis was $55\;{\mu}g/cm^2\;hr$. It increased about 2 folds to $100\;{\mu}g/cm^2\;hr$, when the amount of PGML used was 9%. Large increase in flux and the decrease in time to reach maximum flux were observed when the skin was pretreated with neat PGML (maximum flux obtained was about $200\;{\mu}g/cm^2\;hr$). Use of adhesive decreased the flux significantly. To the contrary of our expectation, increase in current density decreased the flux. These flux data together with the stability data indicate that, though the onset of sufficient delivery occur after 1-2 hours of application, therapeutic amount of $PGE_1$ can be delivered through skin using iontophoresis and penetration enhancer.

• International Journal of Control, Automation, and Systems
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• 제4권4호
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• pp.414-427
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• 2006

This paper presents an adaptive feedback linearization control scheme for induction motors with simultaneous variation of rotor and stator resistances. Two typical modeling techniques, rotor flux model and stator flux model, have been developed and successfully applied to the controller design and adaptive observer design, respectively. By using stator fluxes as states, over-parametrization in adaptive control can be prevented and control strategy can be developed without the need of nonlinear transformation. It also decrease the relative degree for the flux modulus by one, thereby, yielding, a simple control algorithm. However, when this method is used for flux observer, it cannot guarantee the convergence of flux. Similarly, the rotor flux model may be appropriate for observers, but it is not so for adaptive controllers. In addition, if these two existing methods are merged into overall adaptive control system, it brings about structural complexies. In this paper, we did not use these two modeling methods, and opted for the airgap flux model which takes on only the positive aspects of the existing rotor flux model and stator flux model and prevents structural complexity from occuring. Through theoretical analysis by using Lyapunov's direct method, simulations, and actual experiments, it is shown that stator and rotor resistances converge to their actual values, flux is well estimated, and torque and flux are controlled independently with the measurements of rotor speed, stator currents, and stator voltages. These results were achieved under the persistent excitation condition, which is shown to hold in the simulation.

• 한국습지학회지
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• 제16권3호
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• pp.347-353
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• 2014

여과분리형 생물반응조 운전에서 발생하는 flux 감소 원인을 분석하였고, 상등수 수질과 침강성 변화가 flux에 미치는 영향을 평가하였다. 또한 여과막 모듈과 역세정 장치 일체형 시스템의 특성을 평가하였다. 반응조는 17L 유효 용적의 아크릴 반응조에 $100{\mu}m$ 공경의 여과막 모듈을 통해 배출되는 여과시스템으로, 여과시간이 경과함에 따라 상등수의 수질 특히 탁도와 TOC의 수질이 악화됨에 따라 flux가 점진적으로 감소하였다. MLSS 농도가 18000mg/L 이상에서는 여과저항이 급격히 증가하였다. 상등수의 수질과 flux와의 관계를 규명하기 위해서는 MLSS 농도가 10000mg/L 이상에서는 곤란함에 따라 5000mg/L이 적절한 것으로 판단된다. 활성슬러지 플록을 파괴시켜 SVI를 250으로 조정하여 여과를 시작한 경우, 상등수의 탁도가 증가하여, 침강성이 악화됨에 따라 flux도 점차 감소하였다. 여과막 모듈과 폭기세정 장치를 일체화한 시스템에서 공기 공급은 30~60초 정도로 설정함이 적정한 것으로 나타났다.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2173-2182
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• 2020

Control valves are widely used to regulate fluid flux in nuclear power plants, and there are more than 1500 control valves in the primary circuit of one nuclear power plant. With their help, the flux can be regulated to a specific level of water or steam to guarantee the energy efficiency and safety of the nuclear power plant. The flux characteristics of the control valve mainly depend on the valve core shape. In order to analyze the effects of valve core shapes on flux characteristics of control valves, this paper focuses on the valve core shapes. To begin with, numerical models of different valve core shapes are established, and results are compared with the ideal flux characteristics curve for the purpose of validation. Meanwhile, the flow fields corresponding to different valve core shapes are investigated. Moreover, relationships between the valve core opening and the outlet flux under different valve core shapes are carried out. The flux characteristics curve and equation are proposed to predict the outlet flux under different valve core openings. This work can benefit the further research of the flux control and the optimization of the valve core for control valves in nuclear power plants.