• Title/Summary/Keyword: Optimal Phase

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Optimal Echo phase of FLASH sequence for Brain Enhancement scan of mouse at 9.4T MRI system (9.4T MRI FLASH Sequence에서 마우스의 뇌 조영증강 검사를 위한 적정 Echo phase)

  • Jeong, Hyunkeun;Kim, Mingi;Nam, Kichang;Jung, Hyundo;Ahn, Chigwon;Kim, Hochul
    • Journal of the Institute of Electronics and Information Engineers
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    • v.54 no.7
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    • pp.115-124
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    • 2017
  • The objective of study was to investigate the optimal echo phase for mouse brain enhancement scan using fast low angle shot (FLASH) sequence of 9.4T magnetic resonance imaging (MRI). For quantification based on this method, an MR phantom experiment and clinical research were done. The phantom experiment was conducted by fabricating three phantoms with different molar concentration of gadolinium to create changes in echo phase of 9.4T FLASH sequence used in mouse brain scans. In the phantom experiment, SSI was 25~27 [arbitrary units, a.u.] in each of 33 phases from $6{\pi}$ to $28{\pi}$, while RSP was 30~100 mmol. MPSI was 47~52 [a.u], while MPP, where MPSI is seen, was 0.8~9 mmol. EPMS was 80.8~108.0%, while ASIMP was formed between 21.1 and 31.8 [a.u]. In the clinical research, Finally, the occurrence rate of artifact that expressed -1 nd +1. The present study was able to quantify the degree of enhancement at FLASH sequence of 9.4T MRI, as well as identify the optimal echo phase during mouse brain enhancement scan.

Scott Transformer Modeling using PSIM on the AC Substation in the Elect ric Railroad (전기철도의 교류 급전변전소에서 PSIM을 이용한 스코트변압기 모델링)

  • Kim, Sung-Dae;Choi, Kyu-Hyoung
    • Proceedings of the KSR Conference
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    • 2010.06a
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    • pp.1892-1897
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    • 2010
  • In three-phase power, when the power is supplied to the single phase load, there is the unbalance of load in the three-phase power. So the scott transformer is used in the power system to supply a single phase load in three-phase power without the unbalance of loads. Especially, the scott transformer is used in the AC substation of electric railroad. Two single phase transformers are combined by T-wiring in the scott transformer. So, two single phase voltage is provided by differing $90^{\circ}$ phase in three-phase power. The selection of related equipment and correction of protective relay are not easy from characteristic of the scott transformer when shunt and ground faults occur. PSIM(Power Electronics Simulator) is optimal simulation software in field of the power electronics and provide the simple and convenient user interface. In this paper, electric model of the scott transformer is suggested and the current of the scott transformer in shunt and ground faults is analyzed. Also, the scott transformer model is demonstrated by using PSIM.

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Separation of Functionalized Heterocyclic Compounds by High Performance Liquid Chromatography(I) (고성능 액체 크로마토그래피에 의한 기능성 헤테로고리화합물의 분리(I))

  • Lee, Kwang-PilI;Cho, Yun Jin;Lee, Young Cheol
    • Analytical Science and Technology
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    • v.10 no.6
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    • pp.408-417
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    • 1997
  • Normal phase or reversed phase liquid chromatographic separation of some structural isomers of functionalized heterocyclic compounds has been carried out by using several different columns and various mobile phases. The optimal experimental conditions for separation of structural isomers were found on a ternary solvent system including alcohol as a modifier. This polar modifier is preferentially adsorbed onto strong adsorption site, leaving a more uniform population of weaker site that then serve to retain the sample. This 'deactivation' of the adsorbent leads to a number of improvements in subsequent separations. The optimal mobile phase system of separation were found on normal phase on structural isomers. Retention mechanism of normal phase system was also studied depending on adsorption strength between solute and stationary phase of column. However, retention factors of reversed phase system were found on hydrophobic interaction with solvophobic effect.

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Evaluation of surface roughness using phase-measuring interferometer for a few ten ${\AA}$ and sub ${\AA}$-rough substrates (위상측정 간섭계를 이용한 수십 ${\AA}$급 및 sub ${\AA}$급 반사경 기판 조도 평가)

  • 조민식;정태호;오문수
    • Korean Journal of Optics and Photonics
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    • v.10 no.4
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    • pp.283-288
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    • 1999
  • We investigated the characteristics of surface roughness evaluation using phase-measuring interferometer for a few ten $\AA$ and sub $\AA$-rough substrates. The influence of phase averaging and intensity averaging on the roughness measurement by phase measuring interferometer was investigated and the optimal number of phase and intensity averaging for the least measurement error was searched. For a few ten $\AA$-rough sample, roughness value did not depend so much on the data averaging. Whereas, measurement error for sub $\AA$-rough sample was significantly improved as the number of phase and intensity averaging increased. At the phase averaging of 30 and the intensity averaging of 20, roughness value that measurement error was minimized was obtained, and it was in good agreement with that by optical heterodyne interferometer. Roughness measurement at the optimal data averaging showed also good repeatability error less than 0.01$\AA$.

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Safety Enhanced Signal Phase Sequence Design of a Rotary with Five Leg Intersection (5지 신호교차로에서의 안전을 고려한 신호현시 설계)

  • 박재완;김진태;장명순
    • Journal of Korean Society of Transportation
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    • v.20 no.7
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    • pp.23-29
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    • 2002
  • Five and more leg intersections have been still in operation in many urban areas. The number of conflicts in five leg intersection is more than four leg intersection. The signal timing design in the five leg intersection should be performed not only to reduce delay but also to increase safety. This paper suggests safety enhanced signal phase sequence design of a rotary with five leg intersection such as phase sequence minimizing the number of conflict points at the rotary with five leg intersections and the phase-length-design procedure by utilizing the Traffic Network Study Tool(TRANSYT). Field data was collected from Gonguptap five leg intersection in Ulsan and TRANSYT-7F was applied for signal timing design model. Optimal signal phase length and sequence of TRANSYT-7F is rearranged based on the Principal of "two moving traffic flows per phase". In conclusion, proposed signal phase design increased delay by 6.2% compared with the optimal signal phase of TRANSYT-7F. However, it could decrease the number of conflict in the five leg intersection by 61.5%.

Optimal Perilune Altitude of Lunar Landing Trajectory

  • Cho, Dong-Hyun;Jeong, Bo-Young;Lee, Dong-Hun;Bang, Hyo-Choong
    • International Journal of Aeronautical and Space Sciences
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    • v.10 no.1
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    • pp.67-74
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    • 2009
  • In general, the lunar landing stage can be divided into two distinct phases: de-orbit and descent, and the descent phase usually comprises two sub-phases: braking and approach. And many optimization problems of minimal energy are usually focused on descent phases. In these approaches, the energy of de-orbit burning is not considered. Therefore, a possible low perilune altitude can be chosen to save fuel for the descent phase. Perilune altitude is typically specified between 10 and 15km because of the mountainous lunar terrain and possible guidance errors. However, it requires more de-orbit burning energy for the lower perilune altitude. Therefore, in this paper, the perilune altitude of the intermediate orbit is also considered with optimal thrust programming for minimal energy. Furthermore, the perilune altitude and optimal thrust programming can be expressed by a function of the radius of a parking orbit by using continuation method and co-state estimator.

A Study on Optimal Sequential Reclosing to Improve Transient Stability in Transmission System (송전계통 과도 안정도 향상을 위한 최적 순차 재폐로에 관한 연구)

  • Gwon, Gi-Hyeon;Oh, Yun-Sik;Park, Ji-Kyung;Jo, Kyu-Jung;Sohn, Seung-Hyun;Kim, Chul-Hwan
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.10
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    • pp.1354-1360
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    • 2013
  • In transmission system, reclosing scheme is very useful method to improve continuity of power supply and reliability of system. Especially, high speed reclosing which is used generally in transmission systems has a benefit improving transient stability. However, the reclosing can jeopardize the stability under the condition having high difference of voltage phase angle between both ends. Thus, this paper proposes optimal sequential reclosing scheme to improve transient stability due to reclosing operation. The optimal sequential reclosing is that each phase is closed sequentially considering transient energy. In this paper, 345kV and 154kV transmission system is modeled using EMTP (ElectroMagnetic Transient Program) to verify the performance and effectiveness of optimal sequential reclosing on transient stability. Also, Integral Square Error(ISE) method is used to assess the transient stability.

40 Gbps RZ Transmission Using Dispersion Compensation of Single-Span in Optical Transmission Links with Multi-Span of Single Mode Fiber

  • Lee, Seong-Real
    • Journal of information and communication convergence engineering
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    • v.9 no.1
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    • pp.32-37
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    • 2011
  • In dispersion management (DM) and optical phase conjugation applied into optical transmission links with multi fiber spans for minimizing the impact of nonlinearity and group velocity (GVD), implementation possibility of DM using only one fiber span for pre- or postcompensation was assessed as a function of duty cycle of RZ pulse and residual dispersion per span (RDPS). It is confirmed that DM with optimal net residual dispersion (NRD) controlled by only one fiber span could be sufficiently applied into optical transmission links, though optimal NRD is more increased than that in transmission links with the general DM scheme of pre- and postcompensation. Thus, it is expected that optical transmission system is simply designed and implemented by applying the proposed DM scheme into real optical transmission links. Also, it is confirmed that the advantageous duty cycle of RZ is 0.5 and RDPS is setting to be small value for the effective transmitting wide signal wavelength range in optical links with optimal NRD controlled by only one fiber span.