• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.56.3-56.3
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• 2017

The Breakthrough Starshot initiative aims to launch gram-scale spacecraft to a speed of v~0.2c, capable of reaching Alpha Centauri and seeing the Earth-like exoplanet, Proxima b, from close distance, in about 20 years. However, a critical challenge for the initiative is the effects of interstellar matter and magnetic field to the relativistic spacecraft during the journey. In this talk, I will first present our evaluation for the damage to the spacecraft by interstellar gas and dust based on a detailed analysis of the interaction of a relativistic spacecraft with the ISM. Second, I will discuss the deflection and oscillation of spacecraft by interstellar magnetic fields. Third, I will discuss the gas drag fore at high energy regime and quantify its effect on the slowing down of the relativistic lightsails. Finally, we will discuss practical strategies to mitigate the damage by interstellar dust and to maintain the spacecraft aiming at the intended target.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.75-78
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• 2003

This study is to investigate the probability to develop the AE Water-reducing agent which can decrease the bleeding by mixing melamine type super-plasticizer(SP) and methyl cellulose(MC) viscosity agent. According to the result, as the mixing ratio of melamine type SP and MC viscosity agent increases, the bleeding is reduced due to a increase of the air content. When the mixing ratio of melamine type SP and MC viscosity agent is 1:2 and 1;3 at the water content of 165kg/$m^3$ and 175kg/$m^3$ respectively, slump and air content are satisfied and bleeding is reduced to some extent, so this is determined as the mixing ratio of AE water reducing agent for reduction of bleeding. It is prove that the developed AE water reducing agent for reduction of bleeding can reduce the amount of bleeding and prohibit the plastic shrinkage crack by slowing down the bleeding speed. Compressive strength of hardened concrete does not make any difference in comparison with plain concrete.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.825-830
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• 2007

For the design and maintenance of highways and road structures, the statistical data are needed for the vehicle, especially heavy truck crossing. So far, static weighing has been used but it needs fixed station, crews, and it takes a lot of time. Also truck mix and headway distances cannot be obtained. Weigh-In-Motion system uses the sensor as a weighing scale and collects the axle weights, axle distances, vehicle types and etc. without stopping or slowing down the vehicle. Objectives of the study is make a determination of WIM Sensor for Implementation of U-Overloaded Vehicle Regulation System.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.752-753
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• 2006

Oil Pump rotor is essential parts for automobile and, it is consisted of drive rotor and driven rotor in general. These parts are requested different properties according to environment. There are 2 types of Oil Pump rotor according to its usage. One is used for electric system, and the other is used for shaft-driven system. Especially, high precision and functionality is required in electric pump, and cost reduction is required in shaft-drive pump without slowing down its performance. This paper is mainly describing about the non-machine treated shaft-drive pump, based on the trial sample producing process.

• ETRI Journal
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• v.33 no.3
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• pp.466-469
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• 2011

As a fine-grained power gating method for achieving greater power savings, our approach takes advantage of the finite state machine with a datapath (FSMD) characteristic which shows sequential idleness among subcircuits. In an FSMD-based power gating, while only an active subcircuit is expected to be turned on, more subcircuits should be activated due to the power overhead. To reduce the number of missed opportunities for power savings, we deactivated some of the turned-on subcircuits by slowing the FSMD down and predicting its behavior. Our microprocessor experiments showed that the power savings are close to the upper bound.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.331-334
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• 2010

The supersonic speeds slowing down by shock waves is a common problem during the transonic region. So how to study the status of shock on the surface of airplane and wings is crucial adjective during transonic region. However, the theoretical and computational transonic flow problems were very hard. This paper introduced using Navier-Stokes Schemes to study characteristics of AGARD Wing 445.6 by ANSYS CFX in transonic region. From simulations results, as the Mach number increases, shock waves appear in the flowfield, getting stronger as the speed increases, these shock waves will lead to a rapid increase in drag.

• Korean Journal of Optics and Photonics
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• v.12 no.5
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• pp.347-351
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• 2001

The neutral sodium atoms have been slowed down to the trap depth by using a Zeeman slower and trapped by the magneto-optical method. The density and the temperature of the trapped atoms are measured, and the frequency region where the trap is available is represented. We controlled the flux of slowed atoms by varying the slowing beam intensity, and we measured the increasing and decreasing rate of trapped atoms. We show that the difference between the increasing and decreasing rate of trapped atoms result from the loss proportional to $N_2$.

• Childhood Kidney Diseases
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• v.25 no.1
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• pp.1-7
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• 2021

Chronic kidney disease (CKD) in children is associated with various complications, including poor growth and development, mineral bone disorder, cardiovascular disease, kidney failure, and mortality. Slowing down the progression of CKD is important since CKD is often not curable. Prospective cohort studies have been conducted to understand the progression and outcomes of CKD in children, and these studies have identified non-modifiable and modifiable risk factors. Recognition of known risk factors and early intervention are important to delay the progression of kidney function decline in children.

• KDI Journal of Economic Policy
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• v.46 no.1
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• pp.1-19
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• 2024

This paper evaluates explanations for China's growth slowdown. The natural tendency for rapidly growing economies to slow down is a major factor, along with problems bequeathed by unbalanced growth, including a declining ICOR, slowing total factor productivity growth, and rising indebtedness. A number of other mechanisms are of lesser importance: demographics, President Xi's centralization of political power and anti-corruption campaign, and U.S. export controls. Sustaining growth in the longer term will require China to step away from investment, debt and export-fueled growth in favor of a balanced growth model with household consumption playing a larger role. Doing so will require hardening of the budget constraints of regional and local governments and restructuring of the nonperforming debts of property and construction companies.

• Progress in Medical Physics
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• v.20 no.4
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• pp.225-234
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• 2009

Geant4 (GEometry ANd Tracking) provides various packages specialized in modeling electromagnetic interactions. The validation of Geant4 physics models is a significant issue for the applications of Geant4 based simulation in medical physics. The purpose of this study is to evaluate accuracy of Geant4 electromagnetic physics for proton therapy. The validation was performed both the Continuous slowing down approximation (CSDA) range and the stopping power. In each test, the reliability of the electromagnetic models in a selected group of materials was evaluated such as water, bone, adipose tissue and various atomic elements. Results of Geant4 simulation were compared with the National Institute of Standards and Technology (NIST) reference data. As results of comparison about water, bone and adipose tissue, average percent difference of CSDA range were presented 1.0%, 1.4% and 1.4%, respectively. Average percent difference of stopping power were presented 0.7%, 1.0% and 1.3%, respectively. The data were analyzed through the kolmogorov-smirnov Goodness-of-Fit statistical analysis test. All the results from electromagnetic models showed a good agreement with the reference data, where all the corresponding p-values are higher than the confidence level $\alpha=0.05$ set.