• Journal of the Korean Society of Earth Science Education
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• v.14 no.3
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• pp.236-247
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• 2021

This study is to investigate the effect of pre-primary teachers' gender and earth science completion while attending high school on the diversity of concepts, the level of conceptual understanding, and misconceptions about seasonal changes. This study was conducted with 71 pre-primary teachers. The conclusion of this study is as follows. First, the area of concepts used by pre-primary teachers to explain seasonal changes showed a greater difference depending on whether or not they completed earth science while attending high school, rather than depending on gender. Second, although there was no significant gender difference in the conceptual level of pre-primary teachers for seasonal change, the group who completed earth science while attending high school had a statistically significantly higher level of conceptual understanding than the group that did not complete it. Third, the ratio of misconceptions related to seasonal change of pre-primary teachers by gender was not significant, but the group who did not complete earth science while attending high school had a statistically significantly higher percentage of misconceptions than the group that completed it. As a result of the above examination, it is judged that the area of concepts, the level of conceptual understanding, and the misconceptions about seasonal changes of pre-primary teachers are more affected by the completion of earth science courses during high school than by gender differences.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.2
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• pp.87-93
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• 2015

Public education on soil and soil science in Korea was reviewed through textbooks written in Korean which were used in the primary schools since 1950's. Numbers of words 흙[heuk], the Korean native word meaning soil, and 토양[土壤, toyang], originated from Chinese characters, were counted, and compared with the textbooks published in 1950's, 1970's, and 1990's, 2010's. The Korean native word "heuk" was used 20 times in 1950's, and increased to 55 times in 1970's. In 1990's version, it was decreased to 31 times and to 20 times in the 2010's version. The first appearance in the 1950's version was in the 3rd grade book, but was in the $1^{st}$ grade books in both 1990's and 2010's. In this recent version, the primary school students met this word on the poet, "Toad, Toad build a house", and "Sprout come out through soil clod". The word, "토양, toyang", originated from Chinese characters, 土壤, appears only 2 times in the $6^{th}$ grade in 2010's version. Authors conclusively recommend children should learn meaning of soil at early stage of primary school easily with positive image.

• Journal of the Korean Society for Heat Treatment
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• v.7 no.4
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• pp.244-252
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• 1994

The morphological changes of primary solid particles as a fuction of process time on Al-Si alloys during semi-solid state processing with a shear rate of 200s were studied. In hypereutectic Al-15.5wt%Si alloy, it was observed that primary Si crystals are fragmented in the early stage of stirring and morphologies of primary Si crystals change from faceted to spherical during isothermal shearing for 60 minutes. In quaternary Al-12.5wt%Si-2.9wt%Cu-0.7wt%Mg alloy system, it was observed both primary silicon and ${\alpha}$-alumunum particles. Microstructural evolution of primary Si crystals was similar to that of the hypereutectic Al-Si alloy but equiaxed ${\alpha}$-Al dendrites are broken into nearly spherical at the early stage of shearing and later stage of the isothermal shearing ${\alpha}$- Al particles are slightly coarsoned by Ostwald ripening. Mechanical properties of Al-Si-Cu-Mg alloy were compared to those from other processes (squeeze casting and gravity casting). After T6 heat treatment, comparable values of hardness were obtained while slightly lower compressive strength values were observed in rheocast alloy. The elongation, on the other hand, exhibited significant increasement of 15% over gravity cast alloy.

• The Korean Journal of Cytopathology
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• v.6 no.2
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• pp.116-124
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• 1995

Eighty cases of malignant effusion were cytologically studied to elucidate the incidence of primary tumor site and cytologic characteristics of each tumor types. Eighty fluid specimens were composed of 43 ascitic, 35 pleural, and 2 pericardial effusion and primary tumor site had been confirmed by histology. The frequent primary sites were stomach(22 cases, 28%), lung(21 cases, 26%), ovary(11 cases, 14%), liver(7 cases, 9%), and breast (4 cases, 5%). The principal malignant tumors were adenocarcinoma (56 cases, 70%), squamous cell carcinoma (7 cases, 9%), liver cell carcinoma (7 cases, 9%), small cell carcinoma (4 cases, 5%), and non-Hodgkin's lymphoma (4 cases, 5%). The distinctive cytologic findings according to primary tumor types were as follows; the gastric adenocarcinomas were mainly characterized by isolated cells and irregular clusters sometimes with signet ring cells. Papillary serous cystadenocarcinoma of ovary showed frequently papillary clusters and occasional psammoma bodies. Breast carcinoma of ductal type showed cell balls with smooth margins. Colonic adenocarcinoma showed rather irregular clusters or palisading pattern of cylindrical cells. Metastatic squamous cell carcinoma, liver cell carcinoma, small cell carcinoma, and non-Hodgkln's lymphoma showed also characteristic features. These findings Indicate that the cytological features observed in the great majority of malignant effusion are similar to those of primary tumor types, which are very helpful to indentify the primary tumor site.

• Journal of Korea Foundry Society
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• v.36 no.2
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• pp.53-59
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• 2016

The effects of ultrasonic melt treatment on the microstructures of aluminum piston were examined at five observation parts having different cooling rates. The microstructure of aluminum piston consisted of primary Si, eutectic Si, and various types of intermetallic compounds. Regardless of cooling rate, the ultrasonic melt treatment transformed dendritic eutectic cells to equiaxed eutectic cells and it decreased the sizes of eutectic Si and intermetallic compounds that exist at eutectic cell boundaries. In the absence of ultrasonic treatment, coarse primary Si particles were severely segregated and its size was increased with decreasing the cooling rate. The ultrasonic treatment decreased the size of primary Si particles from $25.5{\sim}31.0{\mu}m$ to $17.6{\sim}23.1{\mu}m$, depending on the cooling rate. In the presence of ultrasonic treatment, relatively fine primary Si particles were homogeneously distributed throughout the piston. In addition, the ultrasonic treatment increased the population density and area fraction of fine primary Si particles.

• Journal of Communications and Networks
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• v.14 no.2
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• pp.162-168
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• 2012

This paper considers the scenario in which a set of nodes share a common channel. Some nodes have a rechargeable battery and the others are plugged to a reliable power supply and, thus, have no energy limitations. We consider two source-destination pairs and apply the concept of cognitive radio communication in sharing the common channel. Specifically, we give high-priority to the energy-constrained source-destination pair, i.e., primary pair, and low-priority to the pair which is free from such constraint, i.e., secondary pair. In contrast to the traditional notion of cognitive radio, in which the secondary transmitter is required to relinquish the channel as soon as the primary is detected, the secondary transmitter not only utilizes the idle slots of primary pair but also transmits along with the primary transmitter with probability p. This is possible because we consider the general multi-packet reception model. Given the requirement on the primary pair's throughput, the probability p is chosen to maximize the secondary pair's throughput. To this end, we obtain two-dimensional maximum stable throughput region which describes the theoretical limit on rates that we can push into the network while maintaining the queues in the network to be stable. The result is obtained for both cases in which the capacity of the battery at the primary node is infinite and also finite.

• Journal of the Korean Mathematical Society
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• v.54 no.5
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• pp.1505-1519
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• 2017

Assume that M is an R-module where R is a commutative ring. A proper submodule N of M is called a weakly 2-absorbing primary submodule of M if $0{\neq}abm{\in}N$ for any $a,b{\in}R$ and $m{\in}M$, then $ab{\in}(N:M)$ or $am{\in}M-rad(N)$ or $bm{\in}M-rad(N)$. In this paper, we extended the concept of weakly 2-absorbing primary ideals of commutative rings to weakly 2-absorbing primary submodules of modules. Among many results, we show that if N is a weakly 2-absorbing primary submodule of M and it satisfies certain condition $0{\neq}I_1I_2K{\subseteq}N$ for some ideals $I_1$, $I_2$ of R and submodule K of M, then $I_1I_2{\subseteq}(N:M)$ or $I_1K{\subseteq}M-rad(N)$ or $I_2K{\subseteq}M-rad(N)$.

• Journal of Korea Foundry Society
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• v.24 no.2
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• pp.85-93
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• 2004

Mechanical property of hypereutectic Al-Si alloy is changed according to size and distribution of primary Si. Consequently, the study on the refinement for primary Si is progressed for a long time. But such effect of refinement comes out fading phenomena with the lapse of time. Therefore, this study investigated the optimum condition of primary Si refinement for hypereutectic Al-Si alloy. And we observed various primary Si size with P's fading phenomena. The experiment results were as follows. For experiment of primary Si refinement, we made hypereutectic Al-Si alloy with various amounts of P addition. As a result of experiment, we obtained the fine microstructure at 0.01wt.%P. And the optimum condition of P addition, for preventing from growth of primary Si by P fading, is estimated 0.1wt.%P.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.9
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• pp.2081-2100
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• 2013

In this paper, we propose a cooperative hybrid spectrum sharing protocol by jointly considering interweave (opportunistic) and underlay schemes. In the proposed protocol, secondary users can access the licensed spectrum along with the primary system. Our network scenario comprises a single primary transmitter-receiver (PTx-PRx) pair and a group of M secondary transmitter-receiver (STx-SRx) pairs within the transmission range of the primary system. Secondary transmitters are divided into two groups: active and inactive. A secondary transmitter that gets an opportunity to access the secondary spectrum is called "active". One of the idle or inactive secondary transmitters that achieves the primary request target rate $R_{PT}$ will be selected as a best decode-and-forward (DF) relay (Re) to forward the primary information when the data rate of the direct link between PTx and PRx falls below $R_{PT}$. We investigate the ergodic capacity and outage probability of the primary system with cooperative relaying and outage probability of the secondary system. Our theoretical and simulation results show that both the primary and secondary systems are able to achieve performance improvement in terms of outage probability. It is also shown that ergodic capacity and outage probability improve when the active secondary transmitter is located farther away from the PRx.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1537-1544
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• 2020

Molecular dynamics (MD) simulations were conducted to investigate the temperature effects on the primary damage in gallium nitride (GaN) material. Five temperatures ranging from 300 K to 900 K were studied for 10 keV Ga primary knock-on atom (PKA) with inject direction of [0001]. The results of MD simulations showed that threshold displacement energy (E_d) was affected by temperatures and at higher temperature, it was larger. The evolutions of defects under various temperatures were similar. However, the higher temperature was found to increase the peak number, peak time, final time and recombination efficiency while decreasing the final number. With regard to clusters, isolated point defects and little clusters were common clusters and the fraction of point defects increased with temperature for vacancy clusters, whereas it did not appear in the interstitial clusters. Finally, at each temperature, the number of Ga interstitial atoms was larger than that of N and besides that, there were other different results of specific types of split interstitial atoms.