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김장열,윤종철,이춘식 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.1
We designed an in-flight radioactive isotope (RI) beam separator with large acceptance and twostage separation, which is a major feature for next-generation separators today. The large acceptance value made possible efficient production of RI beams while the two-stage separator allowed us to cope with the poor purity of RI beams. The first stage was used for the production and the separation of RI beams, and the second stage was used to identify RI beam species. For the designed separator, we estimated the yield and the purity of several nuclei produced in projectile fragmentation by using the code LISE++ for three different configurations - momentum analysis, momentum analysis plus an energy degrader, and addition of a radio frequency (RF) kicker. We adopted a RF kicker to increase the purity of proton-rich nuclei in the RI beams. Purifications were introduced as figures of merit for the comparison of the purity enhancements for different separation methods. When the RF kicker was combined with the energy degrader, the purifications for selected proton-rich RI beams such as <sup>35</sup>Ca, <sup>56</sup>Ni, <sup>100</sup>Sn, and <sup>129</sup>Sm turned out to be 10 ∼ 2,000 times those for the case when only the momentum analysis was used. In particular, the purifications for <sup>100</sup>Sn and <sup>129</sup>Sm were 2,000 and 200, respectively, for a momentum acceptance of 1%. However, in the case of neutron-rich RI beams such as <sup>58</sup>Ca, <sup>78</sup>Ni, <sup>132</sup>Sn, and <sup>162</sup>Sm, the purifications were insensitive to the RF kicker, but increased with decreasing the momentum acceptance.
Asymmetric Effects of US Housing Price Inflation on Optimal Monetary Policy
김장열,김민영,임기영 국제지역학회 2009 국제지역연구 Vol.13 No.2
This paper studies optimal discretionary monetary policy in the presence of uncertainty in the housing sector. In particular, we allow two possible regimes regarding the evolution of housing price inflation and the effects of housing price inflation on the aggregate demand. Estimation results with the US data confirm the presence of two distinctive regimes, one 'normal' and the other more akin to the housing price 'bubble' state. The optimal policy is 'asymmetric' in that the optimal responses in the 'normal' regime require the central bank to lean against the wind to inflationary pressure from CPI and housing inflation, while the central bank is recommended to accommodate it in the other regime. This paper studies optimal discretionary monetary policy in the presence of uncertainty in the housing sector. In particular, we allow two possible regimes regarding the evolution of housing price inflation and the effects of housing price inflation on the aggregate demand. Estimation results with the US data confirm the presence of two distinctive regimes, one 'normal' and the other more akin to the housing price 'bubble' state. The optimal policy is 'asymmetric' in that the optimal responses in the 'normal' regime require the central bank to lean against the wind to inflationary pressure from CPI and housing inflation, while the central bank is recommended to accommodate it in the other regime.
Numerical and experimental assessments of focused microwave thermotherapy system at 925 MHz
김장열,이광재,김보라,전순익,손성호 한국전자통신연구원 2019 ETRI Journal Vol.41 No.6
This work investigated three‐dimensional (3D) focused microwave thermotherapy (FMT) at 925 MHz for a human tissue mimicking phantom using the time reversal (TR) principle for musculoskeletal disorders. We verified the proposed TR algorithm by evaluating the possibility of 3D beam focusing through simulations and experiments. The simulation, along with the electromagnetic and thermal analyses of the human tissue mimicking phantom model, was conducted by employing the Sim4Life commercial tool. Experimental validation was conducted on the developed FMT system using a fabricated human tissue mimicking phantom. A truncated threshold method was proposed to reduce the unwanted hot spots in a normal tissue region, wherein a beam was appropriately focused on a target position. The validation results of the simulation and experiments obtained by utilizing the proposed TR algorithm were shown to be acceptable. Effective beam focusing at the desired position of the phantom could be achieved.
STAGGERED NOMINAL CONTRACTS: TAYLOR vs. CALVO
김장열,임기영 한국경제학회 2007 The Korean Economic Review Vol.23 No.1
This paper compares the Taylor type and the Calvo type staggering schemes in terms of their implications on the behavior of aggregate price and output following a monetary expansion. In the sticky nominal price case, it is shown that Calvo type staggering implies positive autocorrelations (i.e., monotone dampening) in price and output, while Taylor type staggering implies negative autocorrelations (i.e., oscillatory dampening). In the sticky nominal wage case, however, it is found that both types of staggering generate monotonically dampening responses of price and output. In other words, the qualitative implications of wage stickiness are robust to the choice of staggering schemes.