The Simulation of Reactor Physics Test for the Research Reactor HANARO

Noh, Taewan Research Institute of Science and Technology HONGI 2005 Hongik Journal of Science and Technology Vol.9 No.-

The paper describes the development of a reactor power control algorithm using the program simulator for the simulation of dynamic behavior of a nuclear reactor. Before the full development of the algorithm for the commercial nuclear power plant, the Korean research reactor HANARO was chosen as a sample reactor for the simulation and for the reactor physics test. All the dynamic characteristics of HANARO were mathematically modeled into a computer program and the parameters of the plant components and the algorithm of reactor control system are adjusted to improve the transient performances as well as to satisfy the constraints imposed on the plant. Several physics parameters such as control rod worth, isothermal temperature defect, and power defec are correlated. These parameters were measured in serial order at the same core condition. The transient response of the plant shows satisfactory behavior and are well corresponding to the result of reactor physics test.

EXTRACTION OF TEMPORAL INFORMATION FROM KOREAN PHRASE FOR NATURAL LANGUAGE INTERFACE SYSTEM

Taewan Kim,Taeyoon Kim 한국멀티미디어학회 2006 한국멀티미디어학회 국제학술대회 Vol.2006 No.-

To save computer users from the overhead of learning the computer programming language and to make computer systems available to naive people, high-level user friendliness in computer systems becomes mandatory. Natural language interface has some of the advantages of real natural language, such as familiarity of medium. But major challenges in building a natural language interface include ambiguity and impreciseness. A natural language query may be ambiguous when it can be parsed in different ways. It may contain imprecise terms that have to be processed before an executable query can be generated. In this paper, a extraction method of temporal information from Korean language is proposed. Processing of temporal expressions are important to make natural language interface systems such as querying the information of time table of air flights, theatres, trains and so on.

Menin Enhances Androgen Receptor-Independent Proliferation and Migration of Prostate Cancer Cells

Taewan Kim,정관영,김은지,윤광현,최진미,박재현,김재환,김형식,윤홍덕,Eun-Jung Cho 한국분자세포생물학회 2022 Molecules and cells Vol.45 No.4

The androgen receptor (AR) is an important therapeutic target for treating prostate cancer (PCa). Moreover, there is an increasing need for understanding the AR-independent progression of tumor cells such as neuroendocrine prostate cancer (NEPC). Menin, which is encoded by multiple endocrine neoplasia type 1 (MEN1), serves as a direct link between AR and the mixed-lineage leukemia (MLL) complex in PCa development by activating AR target genes through histone H3 lysine 4 methylation. Although menin is a critical component of AR signaling, its tumorigenic role in AR-independent PCa cells remains unknown. Here, we compared the role of menin in AR-positive and AR-negative PCa cells via RNAi-mediated or pharmacological inhibition of menin. We demonstrated that menin was involved in tumor cell growth and metastasis in PCa cells with low or deficient levels of AR. The inhibition of menin significantly diminished the growth of PCa cells and induced apoptosis, regardless of the presence of AR. Additionally, transcriptome analysis showed that the expression of many metastasis-associated genes was perturbed by menin inhibition in AR-negative DU145 cells. Furthermore, wound-healing assay results showed that menin promoted cell migration in AR-independent cellular contexts. Overall, these findings suggest a critical function of menin in tumorigenesis and provide a rationale for drug development against menin toward targeting high-risk metastatic PCa, especially those independent of AR.

Antiferromagnetically Exchange-coupled Two Phase Magnets : Co/Co₂TiSn

Taewan Kim,Jung Keun Oh 한국자기학회 2008 Journal of Magnetics Vol.13 No.2

The objective of this paper is to review the magnetic and magneto-transport properties of Co/Co₂TiSn consisting of two metallic magnetic phases that are antiferromagnetically exchange-coupled at the phase boundary. The bulk Co/Co₂TiSn system, which has a Co₂TiSn Heusler alloy precipitates in the hexagonal Co matrix, showed an unusual coercivity change with a concurrent change in temperature, and was modeled on the basis of a wall formation caused by exchange coupling at the phase boundary. For measurements of magneto-transport properties, Co/Co₂TiSn thin films that had two-magnet phases were deposited using a magnetron sputtering system with a composite target. The magnetization process in the films is also explained on the basis of the model of wall formation at the phase boundary. Annealed Co/Co₂TiSn films showed a 0.12% GMR effect, indicating the scattering of polarized conduction electrons due to the antiparallel exchange coupling at the phase boundary. The scattering process of conduction electrons at the phase boundary was modeled with relation to the magnetization process.

New Macroscopic Ferrimagnets in the System Co-TbN

Taewan Kim,Jung Keun Oh 한국자기학회 2008 Journal of Magnetics Vol.13 No.1

This study examines a new macroscopic ferrimagnet, Co-TbN. This ferrimagnet, consisting of two metallic phases, Co and TbN, demonstrated the typical macroscopic ferrimagnet properties of a magnetic compensation point and a negative giant magnetoresistance (GMR). The Co-TbN system with 32% TbN composition showed 0.72% GMR in magnetic fields up to 8 kOe at room temperature and 9% GMR in 40 kOe at 250 K. In the Co-TbN system, GMR exhibited a different dependence on temperature from that of ordinary GMR materials whose negative magnetoresistance decreases with increasing temperature. In contrast to ordinary GMR materials whose negative magnetoresistance decreases with increasing temperature, the GMR effect in the Co-TbN system increased with increasing temperature, due to the increase of ferromagnetic alignment of the Co and TbN in the magnetic field caused by the decreased exchange coupling with increasing temperature.

Analytical Modeling for Reinforced Concrete Columns with Relaxed Section Details

Taewan Kim,Yurim Chu,Hong-Gun Park 대한건축학회 2017 Architectural research Vol.19 No.3

In earthquake engineering, dynamic analyses are usually conducted by using a nonlinear analytical model of the entire building in order to identify the performance against earthquakes. At the same time, a large number of dynamic analyses are required to consider uncertainties on analytical models and ground motions. Therefore, it is necessary for the analytical model to be adequate, that is to say, the runtime should not be too long as the entire building is modeled to be in much detail, or the nonlinear model should not yield outputs very far from the actual ones by excluding important behaviors too much. The analytical model is usually developed based on experimental results, which have been already conducted for reinforced concrete columns with relaxed details. Therefore, this study aimed at making analytical models to be able to simulate the hysteretic behavior of the columns simply and easily. The analytical model utilizes a lumped hinge model to represent nonlinear moment-rotation hysteretic behavior of RC columns, which is feasible for nonlinear dynamic analyses usually conducted in earthquake engineering and for matching the analytical model to test results. For the analytical model, elements and material models provided by OpenSees are utilized. The analytical model can define the envelope curve, pinching, and unloading stiffness deterioration, but shortcoming of this model is not to be able to consider axial force-moment interaction directly and to simulate strength deterioration after post-capping completely. However, the analytical model can still represent test results well by considering that the goal of this study is to propose a general way to represent the hysteretic behavior of RC columns with relaxed details, not to provide parameters for a refined hysteretic model that can be just applied case by case.

Initial Magnetization and Coercivity Mechanism in Amorphous Tb<SUB>x</SUB>Co<SUB>1-x</SUB> Thin Films with Perpendicular Anisotropy

Taewan Kim,Hana Lee,Hyun-Yong Lee,Kyoung-il Lee 한국자기학회 2010 Journal of Magnetics Vol.15 No.4

The coercivity mechanism in permanent magnets was analyzed according to the effects of domain nucleation and domain wall pinning. The coercivity mechanism of a TbCo thin film with high perpendicular magnetic anisotropy was considered in terms of the local inhomogeneity in the thin film. The initial magnetization curves of the TbCo thin films demonstrated domain wall pinning to be the main contributor to the coercivity mechanism than domain nucleation. Based on the coercivity model proposed by Kronmuller et al., the inhomogeneity size acting as a domain wall pinning site was determined. Using the measured values of perpendicular anisotropy constant (Ku), saturation magnetization (Ms), and coercivity (Hc), the inhomogeneity size estimated in a TbCo thin film with high coercivity was approximately 9 ㎚.

The Mechanical Properties of Alkali-Activated Slag-Silica Fume Cement Pastes by Mixing Method

Taewan Kim,Choonghyun Kang 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.4

The mixing method is the investigation of the characteristics of alkali-activated cement paste (AACP) with slag and silica fume (SF) of 1: 1. The basic mixing method is ASTM C305, which is defined as 1st-cycle. There are three factors considered in this experiment; (i) the addition of mixing time (2nd-cycle), (ii) the concentration of activator depending on the amount of mixing water, and (iii) the mixing sequence of slag and SF. It was found that the second cycle, the additional mixing time, had the effect of improving the mechanical properties. In addition, accelerated activation through the mixing of slag with a high concentration of alkali solution in the 1st-cycle increases the hydration products and decreases the porosity and increases the mechanical properties. Therefore, it was found that the change of the mixing method in the AACP composed of slag and SF 1: 1 has a great influence on the mechanical properties. As a result, the method of first mixing slag in aqueous solution of high alkali concentration in AASC mixed with slag and SF improves the mechanical properties.

Improvement of a Requirement for Providing Special Boundary Element Considering Feature of Domestic High-rise Shear Walls

Taewan Kim 대한건축학회 2013 Architectural research Vol.15 No.1

The reinforced concrete shear walls are being widely used in the domestic high-rise residential complex buildings. If designed by current codes, the special boundary element is needed in almost all high-rise shear wall buildings. This is because the equation for determining the provision of the special boundary element in the current codes cannot reflect the characteristics of the domestic high-rise shear walls with high axial load ratio and high proportion of elastic displacement to total displacement. In this study, a new equation to be able to reflect the characteristics is proposed. By using the equation, the special boundary element may not be necessary in certain cases so that structural engineers can relieve the burden of installing the special boundary element in every high-rise shear wall.

Two-Phase Magnet in the Co/Co₂MnSn System

Taewan Kim,Hye-in Yim,Hyun-Yong Lee,Kyoung-il Lee 한국자기학회 2011 Journal of Magnetics Vol.16 No.1

This study reports on Co/Co₂MnSn two-phase magnets. The Co/Co₂MnSn two-phase magnet has Co precipitates in a Co₂MnSn Heusler alloy matrix, in which the two phases are exchange-coupled at the phase boundary. The as-casted Co/Co₂MnSn system, which has Co-Mn solid solution precipitates in a Co₂MnSn Heusler alloy matrix, showed that the Co solid solution precipitates are crystallographically coherent and there is exchange coupling at the phase boundary. To form pure Co precipitates by removal of Mn solute atoms in Co-Mn solid solution, annealing was carried out 48 hours at 870℃. After annealing, the low Tc and low magnetization phase of the Co-Mn solid solution became a high Tc and high magnetization phase of hexagonal Co.