• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.41.2-41.2
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• 2019

The B-fields In STar-forming Region Observations (BISTRO 1 and 2) is a large program of the James Clerk Maxwell Telescope (JCMT) using SCUBA-2 and POL-2, starting in 2016. We aim to study the roles of magnetic fields in star formation by observing 32 fields of nearby low-mass and high-mass star forming regions. The angular resolution and the wavelength provided by JCMT (14 arcsecond at 850 micrometer) are ideal to investigate the intermediate scales of magnetic fields (1000-20000 au) associated in cold dense cores and filaments. We report the current status of this project and discuss the magnetic fields of the Serpens Main molecular cloud in which several filaments with various physical properties have been identified.

• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3517-3527
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• 2021

New 80-MW (electric) ultra-long-life sodium cooled fast reactor core having inherent safety characteristics is designed with heterogeneous fuel assemblies comprised of driver and blanket fuel rods. Several options using upper sodium plenum and SSFZ (Special Sodium Flowing Zone) for reducing sodium void reactivity are neutronically analyzed in this core concept in order to improve the inherent safety of the core. The SSFZ allowing the coolant flow from the peripheral fuel assemblies increases the neutron leakage under coolant expansion or voiding. The Monte Carlo calculations were used to design the cores and analyze their physics characteristics with heterogeneous models. The results of the design and analyses show that the final core design option has a small burnup reactivity swing of 618 pcm over ~54 EFPYs cycle length and a very small sodium void worth of ~35pcm at EOC (End of Cycle), which leads to the satisfaction of all the conditions for inherent safety with large margin based on the quasi-static reactivity balance analysis under ATWS (Anticipated Transient Without Scram).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.4
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• pp.637-640
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• 2022

To maximize performance in a high-performance multicore processor system. it is essential to enable effective data communication between processing cores. Data communication between processor nodes can be broadly classified into collective and point-to-point communications. Collective communication comprises scattering and gathering. This paper presents a efficient message scattering and gathering based on processing node status. In the proposed algorithms, the transmission order is changed according to the data size of the pre-existing communication, to reduce the waiting time required until the collective communications begin. From the simulation, the performances of the proposed message scattering and gathering algorithms were improved by approximately 71.41% and 69.84%.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1747-1755
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• 2021

This paper presents floating absorber for safety at transient (FAST) which is a passive safety device for sodium-cooled fast reactors with a positive coolant temperature coefficient. Working principle of the FAST makes it possible to insert negative reactivity passively in case of temperature rise or voiding of coolant. Behaviors of the FAST in conventional oxide fuel-loaded and metallic fuel-loaded SFRs are investigated assuming anticipated transients without scram (ATWS) scenarios. Unprotected loss of flow (ULOF), unprotected loss of heat sink (ULOHS), unprotected transient overpower (UTOP) and unprotected chilled inlet temperature (UCIT) scenarios are simulated at end of life (EOL) conditions of the oxide and the metallic SFR cores, and performance of the FAST to improve the reactor safety is analyzed in terms of reactivity feedback components, reactor power and maximum temperatures of fuel and coolant. It is shown that FAST is able to improve the safety margin of conventional burner-type SFRs during ULOF, ULOHS, UTOP and UCIT.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.613-616
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• 1998

In this paper, a model of a Eddy-current probe coil with a ferrite core in the presence of a half-space with a layer is developed. The half-space with a layer is accounted for by computing the appropriate Green's function by using Bessel transforms. Upon introducing equivalent Amperian currents within a core to explain effect to a impedance change in the coil due to a (ferrite) core, we derive a volume integral equation, The integral equation is transformed via the method of moments into a vector-matrix equation, which is then solved using a linear equation solver. Through the above processing, we computed impedance value in a Eddy-current probe coil due to a conductivity change of layer.

• Structural Engineering and Mechanics
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• v.85 no.6
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• pp.709-716
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• 2023

In this paper, the shape factors of cellular meta-material plates (MMPs) having diverse cell arrays have been determined as the first attempt to finally examine their stability and vibrational frequencies. The MMPs are actually constructed from cylindrical or cubic cellular cores and two face sheets. Sandwich-like MMPs with circular and square holes in the face sheets have been selected in such a way that the effective material properties depend on the cellular architectures. For verifying the frequency results, finite element (FE) simulations are done in Abaqus software. Several graphical results have been represented to explore the effects of cellular architectures on vibrational frequencies and dynamic responses of the MMPs. Also, the deflection-frequency and stability curves in the case of forced vibrations have been plotted for diverse cell arrays.

• Steel and Composite Structures
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• v.46 no.5
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• pp.659-667
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• 2023

Nonlinear forced vibration behaviors of sandwich plates having graphene platelets (GPL) based face sheets have been researched in this article. Possessing low weight together with low stiffness, square honeycomb cores are mostly constructed by aluminum. Herein, the square shaped core has been fortified by two skins of GPL-based type in such a way that the skins have uniform and linearly graded GPL dispersions. The square shaped core has the effective material specification according to the relative density concept. The whole formulation has been represented based upon classical plate theory (CPT) while harmonic balance approach is applied for solving the problem and plotting the amplitude-frequency curves. The forced vibration behaviors of such plates are influenced by square-shaped core and the relative density, skin's height and GPL fortification.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.250-253
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• 2011

Chip manufacture nowadays turned their attention from accelerating uniprocessors to integrating multiple cores on a chip. Moreover desktop graphic hardware is now starting to support general purpose computation. Desktop users are able to use multi-core CPU and GPU as a high performance computing resources these days. However exploiting parallel computing resources are still challenging because of lack of higher programming abstraction for parallel programming. The 2-dimensional discrete cosine transform (2D-DCT) algorithms are most computational intensive part of JPEG encoding. There are many fast 2D-DCT algorithms already studied. We implemented several algorithms and estimated its runtime on multi-core CPU and GPU environments. Experiments show that data parallelism can be fully exploited on CPU and GPU architecture. We expect parallelized DCT bring performance benefit towards its applications such as JPEG and MPEG.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.23-26
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• 2022

In this paper, our ray tracing hardware is implemented on the latest high-capacity FPGA board. The system included ray tracing hardware for rendering and tree building hardware for handling dynamic scenes. The FPGA board used in the implementation is a Xilinx Alveo U250 accelerator card for data centers. This included 12 ray tracing hardware cores and 1 tree-building hardware core. As a result of testing in various scenes in Full HD resolution, the FPS performance of the proposed ray tracing system was measured from 8 to 28. The overall average is about 17.7 FPS.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05b
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• pp.67-70
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• 2011

The effect of column shortening is a major consideration in design and construction of tall buildings, especially in concrete and composite structural systems. To avoid unexpected demage in structural and nonstructural elements, differential shortening between vertical members resulting from differing stress levels, loading histories, volume-to-surface ratios and other factors in a high-rise building must be properly considered in the design process. This paper represents analyzed and measured shortening results of RC cores and columns at the 72 story Haeundae I'Park. It shows that WACS program based on ACI and PCA material model is effective for the prediction of column shortening.