• Title/Summary/Keyword: Transient State

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A Study on the Development of 2-Dimensional Numerical Wave Tank by the High-Order Spectral Method (고차 스펙트럴법에 의한 2차원 수치 파수조 개발에 관한 연구)

  • Y.J. Kim;J.H. Hwang
    • Journal of the Society of Naval Architects of Korea
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    • v.29 no.3
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    • pp.131-139
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    • 1992
  • By introducing a body potential, the high-oder spectal method of Dommermuth and Yue(1987) is extended to treat the nonlinear interactions between the free surface and the submerged cylinder. A 2-dimensional numerical wave tank is developed based on this numerical scheme, and applied to the wave resistance problem and the wave maker problem. In the simulations, it is shown that the transient waves due to the impulsive start of the body motion make a practical obstacle to the acquisition of useful data from the numerical experiments. Gradual starting procedures are devised, and successful result of the quasi-steady state or the uniform regular wave group was obtained. Within the author's present knowledge, the present numerical scheme is one of the most efficient numerical schemes which can treat the nonlinear interactions between the free surface and the body motion in time-domain.

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The modulation of TRPV4 channel activity through its Ser 824 residue phosphorylation by SGK1

  • Lee, Run-Jeoung;Shin, Sung-Hwa;Chun, Jae-Sun;Hyun, Sung-Hee;Kim, Yang-Mi;Kang, Sang-Sun
    • Animal cells and systems
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    • v.14 no.2
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    • pp.99-114
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    • 2010
  • With the consensus sequence information of the serum glucocorticoid-induced protein kinase-1 (SGK1) phosphorylation site {R-X-R-X-X-(S/T)$\Phi$; where $\Phi$ is any hydrophobic amino acid}, we noticed that the transient receptor potential vanilloid 4 (TRPV4) cation channel, a member of the TRP vanilloid subfamily, harbors the putative SGK1 phosphorylation site (on its Ser 824). We have demonstrated that TRPV4 is an SGK1 authentic substrate protein, with the phosphorylation on the Ser 824 of TRPV4 by SGK1. Further, using TRPV4 mutants (S824A and S824D), we noted that the modification of the Ser 824 activates its $Ca^{2+}$ entry, and sensitizes the TRPV4 channel to 4-$\alpha$-phorbol 12,13-didecanoate (4-${\alpha}PDD$) or heat, simultaneously enhancing its active state. Additionally, we determined that the modification of the Ser 824 controls both its plasma membrane localization and its protein interactions with calmodulin. Thus, we have proposed herein that phosphorylation on the Ser 824 of TRPV4 is one of the control points for the regulation of its functions.

A Pilot Study on the Muscle Activities in Step Input Test as an Indicator of the Vehicle Characteristics

  • Kong, Yong-Ku;Jung, Myung-Chul;Lee, In-Seok;Hyun, Young-Jin;Kim, Chang-Su;Seo, Min-Tae
    • Journal of the Ergonomics Society of Korea
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    • v.32 no.3
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    • pp.217-227
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    • 2013
  • Objective: The purpose of this study was to analyze 'response time', 'peak response time' and 'overshoot value' for each muscle by applying the EMG signal to the vehicle response in ISO 7401 and to quantify the response of the driver according to vehicle characteristics by comparing vehicle characteristics and muscle responses of the driver. Background: The Open-loop test defined in international standards ISO 7401 is the only method for evaluating the performance of the vehicle. However, this test was focused only on mechanical responses, not driver's ones. Method: One skilled male driver(22 yrs. experience) was participated in this experiment to measure muscle activities of the driver in transient state. Then the seven muscle signals were applied to calculate 'response time', 'peak response time', and 'overshoot value'. Results: In the analyses of the EMG data, the effects of vehicle type and muscle were statistically significant on the 'response time' and 'peak response time'. Also, the effects of vehicle type, muscle, and lateral acceleration level were statistically significant on the 'overshoot value' in this study. According to the analyses of the vehicle motion data, vehicle motion variable(LatAcc, Roll, YawVel) was statistically significant on the 'response time' and vehicle type, vehicle motion variable, and lateral acceleration level were statistically significant on the 'peak response time', respectively. Conclusion: In the analyses of the 'response time' and 'overshoot value', the data of muscle activities(EMGs) was better index that could evaluate the vehicle characteristic and performance than the data of vehicle motion. In case of peak response time, both EMG and vehicle motion data were good index. Application: The EMGs data from a driver might be applicable as index for evaluation of various vehicle performances based on this study.

The Effect of Pressure on the $S_F2$ Cleavage Reaction of Tetramethyltin with Iodine (Tetramethyltin과 Iodine의 $S_F2$ 분해반응에 대한 압력의 영향)

  • Oh Cheun Kwun;Jin Burm Kyong;Young Hoon Lee
    • Journal of the Korean Chemical Society
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    • v.37 no.3
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    • pp.287-293
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    • 1993
  • Ultraviolet spectrophotometric investigation has been carried out on the system of charge-transfer(CT) complex with iodine and tetramethyltin in n-hexane and acetone. From these results, the transient CT absorption spectrum can be observed and the subsequent disappearance of CT absorption spectrum is accompained by the cleavage of tetramethyltin with iodine (iododestannylation). Therefore, the rate constants for the iododestannylation were determined at 10, 25 and 35$^{\circ}C$ up to 1600 bar and the rates of reaction were increased with increasing temperature and pressure. From these rate constants, the values of the activation parameters (${\Delta}V^{\neq}$, ${\Delta}{\beta}^{\neq}$, ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$) were obtained and discussed in terms of solvent structure variation of transition state and mechanism from these values. It could postulated that the reaction is followed with S$_F$2 mechanism and weakened S$_F$2 mechanism nature by increasing pressure.

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Base-Catalyzed Rearrangement of Some 1,3-Oxathiolane Sulfoxides: Mechanistic Viewpoint of the Sigmatropic and Elimination Reactions

  • Hahn, Hoh-Gyu;Nam, Kee-Dal;Cheon, Seung-Hoon
    • Bulletin of the Korean Chemical Society
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    • v.25 no.9
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    • pp.1379-1384
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    • 2004
  • Rearrangements of 1,3-oxathiolane sulfoxides 8 and 9 in the presence of base are described from a mechanistic viewpoint of sigmatropic and elimination reactions. In the presence of triethylamine the (Z)-sulfoxide 8 gave the corresponding thiolsulfinate 10 by way of dimerization of the sulfenic acid intermediate 2 at room temperature while the (E)-sulfoxide 9 was recovered even after refluxing in ethyl acetate by the reversal of the [2,3]-sigmatropic rearrangement of the sulfenic acid 4. Triethylamine promoted the developing charge separation in the transition state of the sigmatropic rearrangement of the (Z)-sulfoxide 8 to facilitate the ring opening to the sulfenic acid 2. The reason for more facile ring opening of the (Z)-sulfoxide 8 in comparison with the corresponding (E)-sulfoxide 9 is attributable to the differences in the reactivity of the hydrogen adjacent to the carbonyl group. Triethylamine was not strong base to deprotonate the carbonyl-activated methylene hydrogen of the (E)-sulfoxide 9 but enough to catalyze the sigmatropic process of the sulfoxides. The sulfenic acid 2 dimerized to the thiolsulfinate 10 while the sulfenic acid 4 proceeded the sigmatropic ring closure. In the presence of strong base such as potassium hydroxide, the elimination reaction was predominant over the sigmatropic rearrangement. In this reaction condition, both sulfoxides 8a and 9a gave a mixture of the disulfide 12, the isomeric disulfide 14, and the sulfinic acid 13. Under the strong alkaline condition an elimination of activated hydrogen from the carbon adjacent to the carbonyl group to furnish the sulfenic acid 2a and the isomeric sulfenic acid 18. The formation of the transient intermediate in the reaction was proven by isolation of the isomeric disulfide 14. The reactive entity was regarded as the sulfenic acid rather than sulfenate anion under these reaction conditions.

The Effect of Pressure on the Electrophilic Substitution Reaction of Tetramethyltin with Iodine (Tetramethyltin과 Iodine의 친전자 치환반응에 대한 압력의 영향)

  • Kwun Oh Cheun;Lee Young Hoon
    • Journal of the Korean Chemical Society
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    • v.37 no.6
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    • pp.555-561
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    • 1993
  • Ultraviolet spectrophotometric investigation has been carried out on the system of iododestannylation iodine and tetramethyltin in methanol. The transient CT absorption spectrum can be observed and the subsequent disappearance of CT absorption spectrum was accompained by the cleavage of tetramethyltin with iodine. From there, the rate constants for the iododestannylation were determined at 10, 25 and 35$^{\circ}C$ up to 1600 bar and the reaction rates were increased with increasing temperature and pressure. From these rate constants, the values of the activation parameters (${\Delta}V^\neq,\;{\Delta}{\beta}^{\neq},\;{\Delta}H^{\neq},\;{\Delta}S^{\neq}\;and\;{\Delta}G^{\neq}$) were obtained. The activation volumes and activation compressibility coefficients were both negativity. The activation enthalpies were positive and activation entropies had large negative values. From these values discussed in terms of solvent structure variation of transition state and mechanism. From these results, it was found that the reaction is followed with $S_E2$ mechaenism and weakened $S_E2$ mechanism nature by increasing pressure.

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Thermal Analysis of Prelaunch Transients in Cryogenic Oxidizer Tank of Liquid Propulsion Rocket (발사대기 중인 액체추진 로켓의 극저온 산화제 탱크 내 비정상 열해석)

  • Kim, Kyoung-Hoon;Ko, Hyung-Jong;Kim, Kyoung-Jin;Cho, Kie-Joo;Oh, Seung-Hyub
    • Journal of the Korean Society of Propulsion Engineers
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    • v.12 no.4
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    • pp.33-41
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    • 2008
  • The prelaunch thermal transients in the cryogenic oxidizer tank of liquid propulsion rocket subjected to uniform heat flux from outside are numerically analyzed through thermodynamic equations and heat and mass transfer relations. The prelaunch stage is assumed to be composed of five idealized sub-stages including pressurization process by helium gas injection. The Peng-Robinson equation of state is utilized in the lumped analysis of ullage gas. The liquid region is divided into a number of horizontal layers of uniform properties to account for the thermal stratification. The computational result for the typical case shows that the temperature rise of liquid oxidizer is less than 1K and the adsorbed helium into the liquid is approximately 10g.

DNBR Sensitivities to Variations in PWR Operating Parameters (가압경수로의 운전변수 변화에 대한 DNBR의 민감도)

  • Hyun Koon Kim;Ki In Han
    • Nuclear Engineering and Technology
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    • v.15 no.4
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    • pp.236-247
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    • 1983
  • Analyzed are the the DNBR(Departure from Nucleate Boiling Ratio) sensitivities to variations in various PWR operating parameters utilizing the Korea Nuclear Unit 1(KNU-1) design and operating data. Studied parameters in the analysis are core power level, system pressure, core inlet flow rate, core inlet temperature, enthalpy rise hot channel factor, and axial power peaking factor and axial offset. The calculations are performed using the steady state and transient thermal-hydraulics computer program, COBRA-IV-K, which is the revised version of COBRA-IV-i that has been adapted, partially modified and verified at KAERI. A reference case is established based on the design and operating condition of the KNU-1 reactor core, and this provides a basis for the subsequent sensitivity analysis. From the calculation results it is concluded that the most sensitive parameter in the DNBR thermal design is the coolant core inlet temperature while the axial power peaking factor is the least sensitive.

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Precise Temperature Control of Oil Coolers with Hot-gas Bypass Manner for Machine Tools Based on PI and Feedforward Control (PI와 피드포워드 제어를 이용한 공작기계용 오일쿨러의 핫가스 바이패스 방식 정밀 온도 제어)

  • Jeong, Seok-Kwon;Byun, Jong-Yeong;Kim, Sang-Ho;Yoon, Jung-In
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.2
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    • pp.111-119
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    • 2011
  • Recently, the performances of speed and accuracy are enhanced in machine tools. The high speed of the machine tools usually causes harmful thermal displacements on the objects. To reduce the thermal displacements, machine tools generally adopt oil coolers with precise temperature control function. This study aims at precise control of oil outlet temperature in the oil coolers with hot-gas bypass manner based on PI control logic. The control system was designed for obtaining steady state error within ${\pm}0.1^{\circ}C$ and maximum overshoot with 0.8% even though abrupt disturbances are added to the system. We showed that the PI gains could be easily decided by numerical simulations using practical transfer function which got experiments. Also, transient characteristics could be improved significantly by reflecting the inlet temperature of an evaporator to the output of a controller feedforwardly considering periodic abrupt disturbances. Through some experiments, excellent control performances were established by the suggested control.

Fabrication of New Co-Silicided Si Field Emitter Array with Long Term Stability (Co-실리사이드를 이용한 새로운 고내구성 실리콘 전계방출소자의 제작)

  • Chang, Gee-Keun;Kim, Min-Young;Jeong, Jin-Cheol
    • Korean Journal of Materials Research
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    • v.10 no.4
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    • pp.301-304
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    • 2000
  • A new triode type Co-silicided Si FEA(field emitter array) was realized by Co-silicidation of Co coated Si FEA and its field emission properties were investigated. The field emission properties of the fabricated device through the unit pixel with $45{\times}45$ tip array in the area of $250{\mu\textrm{m}}{\times}250{\mu\textrm{m}}$ under high vacuum condition of $10^{-8}Torr$ were as follows : the turn-on voltage was about 35V and the anode current was about $1.2\mu\textrm{A}(0.6㎁/tip)$ at the bias of $V_A=500V\;and\; V_G=55V$. The fabricated device showed the stable electrical characteristics without degradation of field emission current for the long term operation except for the initial transient state. The low turn-on voltage and the high current stability of the Co-silicided Si FEA were due to the thermal and chemical stability and the low work function of silicide layer formed at the surface of Si tip.

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