• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1266-1276
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• 2021

The mask parameters of a coded aperture are critical design features when optimizing the performance of a gamma-ray camera. In this paper, experiments and Monte Carlo simulations were performed to derive the minimum detectable activity (MDA) when one seeks a real-time imaging capability. First, the impact of the thickness of the modified uniformly redundant array (MURA) mask on the image quality is quantified, and the imaging of point, line, and surface radiation sources is demonstrated using both cross-correlation (CC) and maximum likelihood expectation maximization (MLEM) methods. Second, the minimum detectable activity is also derived for real-time imaging by altering the factors used in the image quality assessment, consisting of the peak-to-noise ratio (PSNR), the normalized mean square error (NMSE), the spatial resolution (full width at half maximum; FWHM), and the structural similarity (SSIM), all evaluated as a function of energy and mask thickness. Sufficiently sharp images were reconstructed when the mask thickness was approximately 2 cm for a source energy between 30 keV and 1.5 MeV and the minimum detectable activity for real-time imaging was 23.7 MBq at 1 m distance for a 1 s collection time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.9
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• pp.775-783
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• 2017

In this paper, an impulsive rendezvous problem by using minimum energy of spacecraft in different orbits is addressed. In particular, the orbits considered in this paper are the general orbits including the elliptic orbit, while most of the orbits considered in the literature have been restricted within co-planar or circular orbits. The constraints for solving this optimization problem are the Kepler's equation formulated with the universal variable, and the final position and velocity of two spacecraft. Also, the Lagrange coefficients, sometimes called as f and g solution, are used to describe the orbit transfer. The proposed method technique is demonstrated through numerical simulation by considering the minimum energy, and both the minimum energy and the wait time, respectively. Finally, it is also verified by comparing with the Hohmann transfer known as the minimum energy trajectory. Although a closed-form solution cannot be obtained, it shows that the suggested technique can provide a new insight to solve various orbital transfer problems.

• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.261-277
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• 2005

We propose the PAD (Power Aware Data-centric Routing Protocol), which finds minimum energy routes and prolongs network life-time, for the data-centric sensor networks. Firstly, the PAD discovers the minimum energy Property graph by removing redundant communication links. The proposed a1gorithm to find the minimum energy property graph is faster, simpler and easier to implement than existing aIgorithms. Secondly, the PAD runs the DDBF (Distributed Data-centric Bellman-Ford Algorithm) to determine routing paths between a base node and all sensor nodes. The DDBF selves the drawbacks of the distributed bellman-ford algorithm, i.e. slow convergence and a possible cyclic routing path. Since the PAD is a fully distributed algorithm with low overhead, it can be used in various kinds of resource limited sensor network applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1C
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• pp.32-36
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• 2003

Based on oriented minimum output energy (OMOE) criterion, a new blind multiuser receiving scheme of linear minimum mean square error (MMSE) detector is proposed, then an adaptive algorithm for implementing the new scheme is given by the steepest descent method, and the convergence property of the algorithm is analyzed in this paper. The numerical results demonstrate the performance of the proposed scheme.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.125-126
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• 2012

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.20-26
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• 2005

A running-profile generation method has been developed that efficiently generates the minimum-energy running profile, even in railway lines which have complicated speed limit sections. In the developed method, the problem of minimizing energy consumption is formulated as a resource allocation problem by dividing a running profile into several blocks, and is solved by the incremental method. A concept of Uni-Braking Block (UBB) which has only one brake section within it is introduces for the formulation. This paper proposes a specific method for running profile in the railway lines by using UBB. And proposes the algorithm to generate the running profile with minimum-energy.

• Progress in Superconductivity
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• v.8 no.2
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• pp.193-201
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• 2007

Since the margins for the minimum quench energy and for the operating current in the superconducting magnet determine the operating regime of the magnet, a thermal stability analysis for the KSTAR superconducting magnet system is performed using 1-D Gandalf code. The result shows that the minimum quench energy is about 500 mJ/cc and the operating current margin is about 70 %. These values are larger than those of the KSTAR design criteria and the KSTAR superconducting magnet system can be operated stably under various experimental environments.

• Journal of the Korean Solar Energy Society
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• v.25 no.4
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• pp.119-123
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• 2005

The main purpose of this study is to define an optimum slope of the roof that demands minimum cooling load of the building, when the roof is affected by the solar and wind energy. Two different roof shapes were chosen: hip, gabled. The cooling load of building having those roof shapes was calculated through the computer simulation, using DOE program. For the simulation, the angle of the roof and angle of the orientation was changed. In the conclusion of this paper, an optimum slope of the roof which causes minimize cooling load is presented according to the roof shape and orientation. The result of this study could provide a practical design guideline for determining the roof angle for various climatic conditions.

• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.95-100
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• 2000

This study was performed in Hartmann type dust explosion apparatus in order to research the dust explosion characteristics of hydroxypropyl methyl cellulose(HPMC): minimum explosive limit, minimum ignition energy, limiting oxygen concentration, maximum explosion pressure, rate of pressure rise, etc. The samples of HPMC dust were distributed into 120-140 mesh, 170-230 mesh and 325 under, and the gap distance of the discharge electrode was setted up at 5mm. The experimental results were obtained as follows: (1) The minimum explosive limit for HPMC dust was founded at 180g/㎥. the minimum ignition energy at 9.8mJ and the limiting oxygen concentration at 12%. (2) The maximum explosion pressure of HPMC dust was $8.1kg/cm^2\;{\cdot}\;$abs at the concentration of $500g/m^3$ and the maximum rate of pressure rise was 203.98 bar/sec at the concentration of $480g/m^3$ for 325 under.

• Journal of the Korean Society of Safety
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• v.16 no.3
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• pp.83-88
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• 2001

This study was preformed by measuring the minimum ignition temperature of MBS according to the change of sample vessel size and the minimum ignition temperature of MBS dust cloud The minimum ignition temperature of MBS product decreased as the vessel size was large, and it was obtained in the range from $120.5^{\circ}C$ to $94.5^{\circ}C$ and the apparent activation energy was obtained with 32.94Kcal/mol. The minimum ignition temperature of MBS dust cloud was measured by using Godbert-Greenwald furnace and it was obtained at $407^{\circ}C$ with the sample of 0.4g in the air and the ignition of dust cloud was not occurred below 13% oxygen concentration.