• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.321-328
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• 2009

Shock absorption performances of various rubbers were investigated by using drop impact test. Several types of rubber such as NR, NBR, EPDM, SR and PUR with three respective levels of shore hardness were used for the test. As in the cases, the absorbed impact energies in rubbers were measured under seven different loads against impact energy between 5-80J. The impact absorption efficiencies of the rubbers then were evaluated by means of both single impact energy condition and summation of all impact energy applied condition. As shown in the results, PUR and EPDM have better shock absorption performances than other rubbers. Further analysis was extended to determine a shear modulus of SR through the finite element implementation with Blatz-Ko model. As can be seen, relatively higher level of absorption energy results in a decreasing shear modulus.

• Journal of the Korean Society of Safety
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• v.21 no.2 s.74
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• pp.107-113
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• 2006

Earthquake motion is one of the most significant influence factors on the slope stability. In this paper, an effective stress analysis with the elasto-plastic model was carried out to investigate the behavior of the slope stability subjected to the successive two strong earthquake motions, fore and main shock. The major influence of fore shock to the slope stability was considered as the existence of the residual excess pore water pressure. The paper presents the influence of the existence of the fore shock to slope stability using the numerical analyses. In conclusion, the excess pore pressure by the fore shock was not dissipated during the 7hrs of consolidation. By this residual excess pore water pressure, the factor of safety at the sliding face showed the minimum values, and the deformations of slope was large when compared with the case that considered the main shock only. Furthermore, the minimum of the factor of safety came out after the end of the earthquake motion.

• Journal of the Korean Society of Safety
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• v.16 no.3
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• pp.53-60
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• 2001

This paper presents a graphical method for hazard assessment of electric shock by safety criteria. For the human body to be safety actual body current should not exceed safety criteria, i.e. allowable body current. The assessment method presented in this paper is based m the safety criteria of the IEEE Standard 80 as well as the IEC 479-1. The hazard can be assessed in terms of alterable touch voltages instead of alterable body current. Thus, the hazard assessment of given electric shock condition is referred to a procedure by which the actual touch voltages are compared with the allowable (safe) touch voltages. Since the IEC 479-1 safety criteria are nonlinear, the graphical method is presented for the hazard assessment. Body current and body voltage are calculated with the allowable touch voltage. A comparison of the safety criteria of two widely accepted standards, i.e. the IEEE Std 80 End the IEC 479-1 is proposed. Also Thevenin equivalent resistance is obtained from electric shock model expressed by two-port earth-grid-foot system. On the basis of calculated results, the allowable touch voltage, the body current and the body voltage we can conduct the hazard or safety assessment and estimate the severity of electric shock.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.114.1-114.1
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• 2012

To measure the magnetic field strength in the solar corona, we examined 10 fast (>1000 km/s) limb coronal mass ejections (CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3-15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49-3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47-1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6-105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfven speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.146-154
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• 2009

Dynamic response of a hull mounted sonar(HMS) to shocks transmitted through hull structures is analyzed and then the structural reliability of the sonars is evaluated. Finite element model of the hull mounted sonar is established and the transient responses to the shock is calculated using MSC.NASTRAN. According to BV043, the maximum allowable accelerations at the foundation of the sonar are converted from the shock spectra allowable for HMS. They are applied vertically and horizontally, respectively, using the large mass method. The structural reliability is evaluated by comparing the von-Mises stresses with the material yield stress. The drum for sensors shows a high reliability owing to mounts by which the shock waves from the base structure are well protected. However, the mounts between the base structure and the drum to mount sensors show a high stress intensity. The base structure also reveals a high stress intensity at the connection points to the hull.

• Asia-Pacific Journal of Business
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• v.13 no.3
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• pp.343-359
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• 2022

We analyze the regional ripple effects of both the sale prices and cheonsei prices using the global VAR(GVAR) model. The interest rate shock causes the regional sale prices to fall. Moreover, the greatest responses to the shock are those of Gangnam-gu, etc. because of there were many transactions for investment purpose. When interest rate rose, the cheonsei price in Gangnam-gu reacted greatly. Conversely, if interest rates fall, the cheonsei demand to live in Gangnam-gu increases. Furthermore, the response of sale price to the interest rate shock are greater than those of the cheonsei prices. Whereas, a positive shock on the sale price in Gangnam-gu increases the sale price there. It also raises the sale prices of the surrounding area in a similar pattern. The shock on the sale price in Gangnam-gu also increases the cheonsei price in Gangnam-gu. In addition, an increase in the sale price in Gangnam-gu leads to increases of cheonsei prices in other regions. Therefore, the recent rise of the base rate can negatively affect the sale prices, and thus a decrease in the sale price spreads to the surrounding areas. Accordingly, it is time for policy alternatives to make a soft landing in sale prices.

• Publications of The Korean Astronomical Society
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• v.12 no.1
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• pp.111-143
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• 1997

We have developed a spherical FCT code in order to simulate the interaction of supernova remnants with stellar wind bubbles. We assume that the density profile of the supernova ejecta follows the Chevalier mode1(1982) where the outer portion has a power-law density distribution($\rho{\propto}\gamma^{-n}$) and the SN ejecta has a kinetic energy of $10^{51}$ ergs. The structure of wind bubble has been calculated with the stellar mass loss rate $\dot{M}=5\times10^{-6}M_{\odot}/yr$ and the wind velocity $\upsilon=2\times10^3$ km/s We have simulated seven models with different initial conditions In the first two models we computed the evolution of SNRs with n=7 and n=14 in the uniform medium The numerical results agree with the Chevalier's similarity solution at early times. When all of the power-law portion of the ejecta is swept up by the reverse shock, the evolution slowly converges to the Sedov-Taylor stage. There is not much difference between the two cases with different n's The other five models simulate SNRs produced inside wind bubbles. In model III, we consider the SN ejecta of 1.4 $M_{\odot}$ and the radius of bubble ~2.76 pc so that ratio of the mass $\alpha(=M_{W.S}/M_{ej}$ is 2. We follow the complex hydrodynamic flows produced by the interaction of SN shocks with stellar shocks and with the contact discontinuities, In the model III, the time scale for the SN shock to cross the wind shell $\tau_{cross}$ is similar to the time scale for the reverse shock to sweep the power-law density profile $\tau_{bend}$. Hence the SN shock crosses the wind shell. At late times SN shock produces another shell in the ambient medium so that we have a SNR with double shell structure. From the numerical results of the remaining models, we have found that when $\tau_{cross}/\tau_{bend}\leq2$, or equivalently when $\alpha\leq50$, the SNRs produced inside wind bubbles have double shell structure. Otherwise, either the SN shock does not cross the wind shell or even if it crosses at one time, the reverse shock reflected at the center accelerates the wind shell to merge into the SN shock Our results confirm the conclusion of Tenorio-Tagle et a1(1990).

• KDI Journal of Economic Policy
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• v.32 no.3
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• pp.1-32
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• 2010

The global financial crisis has exerted enormous impacts on the attainment of inflation target in Korea. The annual average CPI inflation was 3.3% during the targeting period of 2007-2009 and the target was $3.0{\pm}0.5%$. Thus Korea has succeeded in keeping annual average CPI inflation just below the upper limit of the 2007-2009 target under the global crisis. This paper intends to evaluate the performance of the inflation targeting system in Korea. First, it estimates the conventional call rate reaction equation under the global crisis and finds that the policy interest rates never reacted to expected inflation, output gap, and won/dollar exchange rate, as expected by theory. Second, it identifies the shock of global financial crisis into core and non-core, applying the structural VAR model. The core shock was defined to have no (medium- to) long-run impact on real output. The core shock was identified to have the character of the demand shock, since it has the positive impact on the inflation and output in the short run. The structural core inflation due to core shock was an attractor of headline inflation, not vice versa. Therefore, the structural core inflation that reflects the demand-side shock would be the better intermediate target for the final headline inflation target than the official core inflation that excludes the volatile inflation of agricultural and oil-related products. During the inflation targeting period of 2007-2009, the structural core inflation was more volatile than the official core inflation, because the global crisis has very large negative impacts on the domestic demand as well as the prices of agricultural and oil-related products. This paper shows that the negative core shock during the fourth quarter of 2008 was larger than that in the financial crisis in 1998. But the core shock turned into positive very quickly in 2009, as the Korean economy recovered very quickly from crisis. The volatile changes in structural core inflation suggests that the Bank of Korea barely managed to attain the 2007-2009 inflation target, owing to the very large negative impacts of the global financial crisis on the domestic demand. It also suggests that the rapid rise in core inflation with the rapid recovery of the Korean economy will lead to rapid rise in headline inflation.

• International Area Studies Review
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• v.20 no.1
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• pp.3-22
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• 2016

In this study, I examine mutual shock spillover effects among interest rate differences, won-dollar foreign exchange change rates, and stock market returns in Korea during the daily sample period from the beginning of 1995 to the October 16, 2015, using the multivariate GARCH (generalized autoregressive conditional heteroscedasticity) BEKK (Baba-Engle-Kraft-Kroner) model framework. Major findings are as follows. Throughout the 6 model estimation results of variance equations determining return spillovers covered from symmetric and asymmetric models of total sample period and two crisis sub-sample periods composed of Korean FX Crisis Times and Global Financial Crisis Times, shock spillovers are shown to exist mainly from stock market return shocks. Stock market shocks including down-shocks from the asymmetric models are shown to transfer to those other two markets most successfully. Therefore it is most important to maintain stable financial markets that a policy design for stock market stabilization such as mitigating stock market volatility.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.279-290
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• 1998

The height and speed of the shock wave are critical data in flood-control operations or in the design of channel walls and bridges along rivers with high flow velocities. Therefore, a numerical model is needed for simulating flow discontinuity over a wide range of conditions. In this study, a governing equation. As a Riemann solver Roe(1981)'s one is used. The model employs the modified MUSCL for handling the unstructured grids in this research. this model that adopts the explicit tradditional twl dimmensional dam break problems, two hydraulic dam break model is simulations, and a steady state simulation in a curved channel. Conclusions of this research are as follows : 1) the finite volume method can be combined with the Godonov-type method that is useful for modeling shocks. Hence, the finite volume method is suitable for modeling shocks. 2) The finite volume model combined with the modified MUSCL is successful in modeling shock. Therefore, modified MUSCL is proved to be valid.