• BMB Reports
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• 제40권4호
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• pp.554-561
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• 2007

Shen and colleagues (Lin et al., 2004) have recently shown that overexpression of the Drosophila DNA methyltransferase 2 isoform C, dDnmt2c, extended life span of fruit flies, probably due to increased expression of small heat shock proteins such as Hsp22 or Hsp26. Here, I demonstrate with immunoprecipitations that overexpressed dDnmt2c interacts with endogenous Hsp70 protein in vivo in S2 cells. However, its C-terminal half, dDnmt2c(178-345) forms approximately 10-fold more Hsp70-containing protein complexe than wild-type dDnmt2c. Overexpressed dDnmt2c(178-345) but not the full length dDnmt2c is able to increase endogenous mRNA levels of the small heat shock proteins, Hsp26 and Hsp22. I provide evidence that dDnmt2c(178-345) increases Hsp26 promoter activity via two heat shock elements, HSE6 and HSE7. Simultaneously overexpressed Hsp40 or a dominant negative form of heat shock factor abrogates the dDnmt2c(178-345)-dependent increase in Hsp26 transcription. The data support a model in which the activation of heat shock factor normally found as an inactive monomer bound to chaperones is linked to the overexpressed C-terminus of dDnmt2c. Despite the differences observed in flies and S2 cells, these findings provide a possible explanation for the extended lifespan in dDnmt2c-overexpressing flies with increased levels of small heat shock proteins.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 춘계 학술대회논문집
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• pp.39-44
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• 2000

Two-dimensional Navier-Stokes codes are used to simulate the shock tunnel in Konkuk university. In order to design experiments in impulse facilities properly and to interpret data from such facilities, it is necessary to understand how the flow approaches steady state. This is done by determining the transient flow field and flow establishment time around a given model. This will be accomplished by developing appropriate CFD codes which solve the Navier-Stokes equations, and simulating the starting process and resulting unsteady viscous flow phenomena. The starting process in a shock tunnel consists of multiple shock interactions and contact discontinuities, which are difficult to solve with the classical shock capturing schemes. A recently developed high resolution scheme is adapted for resolving the unsteady phenomena of those multiple shock interactions and contact surfaces during the starting process. The bifurcation phenomenon due to the interactions of the reflected shock from the end of the shock tube with the boundary layer generated by the incident shock becomes of particular interest. By comparing with the experiment results, the accuracy of the numerical analysis is validated and it is demonstrated that the properties which can hardly be obtained through the experiment can be estimated.

• The Journal of the Acoustical Society of Korea
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• 제15권4E호
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• pp.72-77
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• 1996

A relatively simple theoretical model for predicting the shock thickness is applied to the weak shock propagation through sea water, where the boric acid and the magnesium sulfate are the major relaxation processes. The relaxation effects increases the shock thickness by the factor of 103 compared with the thickness based on the classical absorption only. In seawater with the ambient pressure of 125 atm and 15℃ temperature, the effects of the boric acid are dominant when the peak pressure is less than 0.3 atm and 3 atm. For the shocks of peak pressure greater than 5 atm, the effects of the classical absorption theory is enough to describe the shock thickness. The effects of the ambient pressure and temperature on the shock thickness are also evaluated.

• 천문학회보
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• 제42권1호
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• pp.36.4-37
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• 2017

Although most of observed properties of giant radio relics detected in the outskirts of galaxy clusters could be explained by relativistic electrons accelerated at merger-driven shocks, a few significant puzzles remain. In some relics the shock Mach number inferred from X-ray observations is smaller than that estimated from radio spectral index. Such a discrepancy could be understood, if either the shock Mach number is nder-estimated in X-ray observation due to projection effects, or if pre-existing electrons with a flat spectrum are re-accelerated by a weak shock, retaining the flat spectral form. In this study, we explore these two scenarios by comparing the results of shock acceleration simulations with observed features of the so-called Toothbrush relic in the merging cluster 1RXS J060303.3. We find that both models could reproduce reasonably well the observed radio flux and spectral index profiles and the integrated radio spectrum. Either way, the broad transverse relic profile requires additional post shock electron acceleration by downstream turbulence.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.29-34
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• 1999

A two-dimensional Navier-Stokes code based on AUSMPW+ scheme has been developed to simulate the hypersonic flowfield of hypersonic shock-shock interaction. AUSMPW+ scheme is a new hybrid flux splitting scheme, which is improved by introducing pressure-based weight functions to eliminate the typical drawbacks of AUSM-type schemes, such as non-monotone pressure solutions. To study the real gas effects, three different gas models are taken into account in this paper: perfect gas, equilibrium flow and nonequilibrium flow. It has been investigated how each gas model influences on the peak surface loading, such as wall pressure and wall heat transfer, and unsteady flowfield structure in the region of shock-shock interaction. With the results, the value of peak pressure is not sensitive to the real gas effects nor to the wall catalyticity. However, the value of peak heat transfer rates is affected by the real gas effects and the wall catalyticity. The structure of the flowfield also changes drastically in the presence of real gas effects.

• 한국정밀공학회지
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• 제20권6호
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• pp.167-177
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• 2003

In this study, a mathematical nonlinear dynamic model is introduced to predict the damping force of automotive shock absorber. And 11 design parameters were proposed for the sensitivity analysis of damping force. Design parameters consist of 5 piston valve design parameters, 5 body valve design parameters and 1 initial pressure of reservoir chamber air. All of these design parameters are main design parameters of shock absorber in the procedure of shock absorber design. The simulation results of this paper offer qualitative information of damping force variation according to variation of design parameters. Therefore, simulation results of this paper can be usefully use in the design procedure of shock absorber

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.425-435
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• 2017

In this work, an overview of flow diagnosis in a shock tunnel is made by means of using established techniques that are easy to setup, economical to arrange, and simple to measure. One flow condition was considered having Mach number of 6 at the nozzle-exit, regarded as freestream. Measured aerothermodynamic data such as shock wave speed, wall static and total pressures, surface heat flux, and shock stand-off distance ahead of test model showed good agreement with calculation. This study shows an overall procedure of flow diagnosis in a shock tunnel in a single manuscript. Outcomes are thought to be useful in the field of education and also in a preliminary stage of high-speed vehicle design and tests, that need to be performed within a short time with decent accuracy.

• KDI Journal of Economic Policy
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• 제44권4호
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• pp.79-108
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• 2022

This study examines the impact of sentiment shock, which is defined as a stochastic innovation to the Housing Market Confidence Index (HMCI) that is orthogonal to past housing price changes, on aggregate housing price changes and housing price volatility. This paper documents empirical evidence that sentiment shock has a statistically significant relationship with Korea's aggregate housing price changes. Specifically, the key findings show that an increase in sentiment shock predicts a rise in the aggregate housing price and a drop in its volatility at the national level. For the Seoul Metropolitan Region (SMR), this study also suggests that sentiment shock is positively associated with one-month-ahead aggregate housing price changes, whereas an increase in sentiment volatility tends to increase housing price volatility as well. In addition, the out-of-sample forecasting exercises conducted here reveal that the prediction model endowed with sentiment shock and sentiment volatility outperforms other competing prediction models.

• Steel and Composite Structures
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• 제27권3호
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• pp.255-271
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• 2018

This paper deals with the transient dynamic analysis and elastic wave propagation in a functionally graded graphene platelets (FGGPLs)-reinforced composite thick hollow cylinder, which is subjected to shock loading. A micromechanical model based on the Halpin-Tsai model and rule of mixture is modified for nonlinear functionally graded distributions of graphene platelets (GPLs) in polymer matrix of composites. The governing equations are derived for an axisymmetric FGGPLs-reinforced composite cylinder with a finite length and then solved using a hybrid meshless method based on the generalized finite difference (GFD) and Newmark finite difference methods. A numerical time discretization is performed for the dynamic problem using the Newmark method. The dynamic behaviors of the displacements and stresses are obtained and discussed in detail using the modified micromechanical model and meshless GFD method. The effects of the reinforcement of the composite cylinder by GPLs on the elastic wave propagations in both displacement and stress fields are obtained for various parameters. It is concluded that the proposed micromechanical model and also the meshless GFD method have a high capability to simulate the composite structures under shock loadings, which are reinforced by FGGPLs. It is shown that the modified micromechanical model and solution technique based on the meshless GFD method are accurate. Also, the time histories of the field variables are shown for various parameters.

• 한국임상수의학회:학술대회논문집
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• 한국임상수의학회 2008년도 춘계학술대회
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• pp.132-132
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• 2008