• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.103-109
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• 2017

An increase in acoustic energy in a combustion chamber coupled with heat fluctuations from flame results in the occurrence of combustion instability. The assessment of combustion stability requires the prediction of acoustic energy variation by understanding the acoustical characteristics of flow boundaries in a combustion chamber. The present paper discusses about the characteristics of acoustic impedances at boundaries in terms of Strouhal number and summarizes theoretical analyses on the acoustic characteristics of injector-head-like configurations. Also, the details of the two-microphone measurement technique have been presented.

• Journal of the Korea Society of Computer and Information
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• v.21 no.11
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• pp.103-111
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• 2016

Traditionally, in the hospital the doctors saw the TRUS images by their eyes and manually segmented the boundary between the prostate and nonprostate. But the manually segmenting process not only needed too much time but also had different boundaries according to the doctor. To cope the problems, some automatic segmentations of the prostate have been studied to generate the constant segmentation results and get the belief from patients. Besides, on detecting the boundary, the ones in the middle of all images are easy to find the boundary but the base and apex of the images are hard to do it since there are lots of uncertain boundary. Accurate detection of prostate boundaries is a challenging and difficult task due to weak prostate boundaries, speckle noises and the short range of gray levels. In this paper, we propose the method that extracts a prostate boundary using features of its directions on prostate image. As a result of our experiments, it shows that the boundary never falls short of the existing methods or human expert's segmentation. And also, its searching speed is too fast because the method searches a smaller area that other methods.

• Journal of Digital Convergence
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• v.11 no.1
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• pp.191-198
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• 2013

The interests in alternative office systems and solutions (called smart work in Korea) are growing. With the lens of boundary theory, this paper tries to understand the nature of work/nonwork boundaries which smart work will be expected to blur. Boundary theory provides permeability, boundary strength, and interference as its key concepts and an empirical study is performed about the individual perception on those concepts. The result of the survey from telecommuters and/or smart work center users at the Company K shows that they perceive work/nonwork permeability, boundary strength, and interference are asymmetric. The result suggests that asymmetric nature of the work/nonwork boundaries should be taken into account when alternative office systems are brought into use.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.6
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• pp.585-591
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• 2015

In transcription for spoken language research, labeling is a work linking text-represented utterance to recorded speech. Most existing labeling tools have been working manually. Semi-automatic labeling we are proposing consists of automation module and manual adjustment module. Automation module extracts voice boundaries utilizing G.Saha's algorithm, and predicts utterance boundaries using the number and length of utterance which established utterance text. For maintaining existing manual tool's accuracy, we provide manual adjustment user interface revising the auto-labeling utterance boundaries. The implemented tool of our semi-automatic algorithm speed up to 27% than existing manual labeling tools.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.3
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• pp.249-262
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• 1989

We present a method of boundary extraction of moving objects. We propose four methods for detecting moving edge pixels which can be located on the boundaries of moving objects. We select the best one after we test the above four methods to real image sequences. The portion of the boundaries of moving objects which is marked as moving edge pixels is searched along the moving edge pixels with simple heuristics. And the end points of the resultant line segments are utilized as the start points of the secon stage heuristic search. This second stage search is performed for the boundaries of moving objects which is not marked as moving edge pixels due to various reasons. We test our algorithm for two real sequences and we find that this simple algorithm has good performance.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.102-109
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• 2000

When PbZrO3 (PZ) and PbTiO3 (PT) particles were scattered on polished surfaces of sintered Pb(Zr0.52Ti0.48)O3 (PZT; Zr/Ti=1.08) and then annealed, the PZT grain boundaries migrated. Near the scattered particles, grain boundaries were corrugated and thus the grain shape changed from a normal one to irregular ones. Especially, near the scattered PZ particles, fast grain growth occurred. In the regions swept by moving grain boundaries, the Zr/Tiratio was measured to be about 1.35 for of PZ scattering and about 0.8 for PT scattering, respectively. This result indicates that the grain boundary migration was induced by alloying of Zr and Ti ions in PZT grains, as in usual diffusion induced grain boundary migration(DIGM). A calculation showed that higher coherency strain energy was induced for PT scattering because of higher alloying of Ti than of Zr.

• Electrical & Electronic Materials
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• v.10 no.7
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• pp.659-667
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• 1997

The influence of SiO$_2$on the microstructure and electrical properties of zinc oxide varistor was investigated. Zn$_2$SiO$_4$third phase in the sintered body was found at grain boundaries, multiple grain junctions, and occasionally within ZnO grains. This phase acted as a grain growth inhibitor, which retard the grain growth of the ZnO matrix by impeding migration on the grain boundaries. As SiO$_2$ addition increases, average grain size decreased from 40.6${\mu}{\textrm}{m}$ to 26.9${\mu}{\textrm}{m}$ due to the pinning effect by Zn$_2$SiO$_4$ and drag effect by Si segregation at grain boundaries, the breakdown voltage consequently increased. When SiO$_2$ addition is increased, interface state density decreased, however, the barrier height increased by decrease of donor concentration, as a result, the nonlinear exponent increased and leakage current decreased. While, as SiO$_2$ addition increase, it was found that the apparent dielectric loss factor shows a tendency of decrease. Wholly, electrical properties of zinc oxide varistor can be said to be improved by SiO$_2$addition.

• Journal of Powder Materials
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• v.17 no.1
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• pp.52-58
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• 2010

Bulk nanostructured metallic materials are generally synthesized by bottom-up processing which starts from powders for assembling bulk materials. In this study, the bottom-up powder metallurgy and High Pressure Torsion (HPT) approaches were combined to achieve both full density and grain refinement at the same time. After the HPT process at 473K, the disk samples reached a steady state condition when the microstructure and properties no longer evolve, and equilibrium boundaries with high angle grain boundaries (HAGBs) were dominant. The well dispersed alumina particles played important role of obstacles to dislocation glide and to grain growth, and thus, reduced the grain size at elevated temperature. The small grain size with HAGBs resulted in high strength and good ductility.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.375-375
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• 2007

In the conventional crystallization method, thepoly-Si TFTs show poor device-to-device uniformity because of the random location of the grain boundaries. However, our new crystallization method introduced in this paper employed substrate-embedded seeds on the highly ordered anodic alumina template to control both the location of seeds and the number of grain boundaries intentionally. In the process of excimer laser crystallization (ELC), a-Si film deposited on the anodic alumina by low pressure chemical vapor deposition (LPCVD) is transformed into fine poly-Si grains by explosive crystallization (XC) prior to primary melting. At the higher energy density, the film is nearly completely melted and laterally grown by super lateral growth (SLG) from remained small part of the fine poly-Si grains as seeds at the Si/anodic alumina interface. Resultant grain boundaries have almost linear functions of the number of seeds in concavities of anodic alumina which have a constant spacing. It reveals the uniformity of. device can be enhanced prominently by controlling location and size of pores which contains fine poly~Si seeds under artificial anodizing condition.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.4052-4059
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• 2021

The microstructure of the fuel pellet plays an essential role in fission gas buildup and release and is critical for the safe and continued operation of nuclear power stations. Structural analysis of uranium dioxide (UO₂)-molybdenum (Mo) composite fuel pellets prepared at a range of sintering temperatures from 1300 to 1800 ℃ was performed. Mo micro and nanoparticles were used in making the composite pellets. A systematic investigation into the influence of processing parameters during Spark Plasma Sintering (SPS) of the pellets on the microstructure, texture, grain size, and grain boundary characters of UO₂-Mo is presented. UO₂-Mo composite show significant differences in the fraction of general boundaries and also special/coincident site lattice (CSL) boundaries. EBSD orientation maps demonstrated that <111> texturing was observed in the pellets fabricated at 1500 ℃. The experimental investigations suggest that UO₂-Mo composite pellets have favorable microstructural features compared to the UO₂ pellet.