• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.87-93
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• 2009

Wireless mesh networks (WMNs) are emerging technologies that provide ubiquitous environments and wireless broadband access. The aggregate capacity of WMNs can be improved by minimizing the effect of channel interference. The IEEE 802.11b/g standard which is mainly used for the network interface technology in WMNs provides 3 multiple channels. We must consider the channel scanning delay and the channel dependency problem to effectively assign channels in like these multi-channel WMNs. This paper proposes a cluster-based channel assignment (CB-CA) algorithm for multi-channel WMNs to solve such problems. The CB-CA does not perform the channel scanning and the channel switching through assigning co-channel to the inter-cluster head (CH) links. In the CB-CA, the communication between the CH and cluster member (CM) nodes uses a channel has no effect on channels being used by the inter-CH links. Therefore, the CB-CA can minimize the interference within multi-channel environments. Our simulation results show that CB-CA can improve the performance of WMNs.

• Journal of The Korean Association For Science Education
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• v.40 no.1
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• pp.61-75
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• 2020

In this study, external representation presented in two units, 'Property of Gas' and 'Changes of States of Matter,' in seventh grade of 2015 revised science curriculum, were analyzed to suggest educational implications. External representations presented in five science textbooks were analyzed according to the six criteria, which were 'type of representation,' 'interpretation of surface features,' 'relatedness to text,' 'existence and properties of a caption,' 'degree of correlation between representations comprising a multiple one,' and 'function of representation.' The characteristics of typical representations related to each achievement standard of two units were also analyzed. The results were as follows: The macro representations for 'type of representation', and explicit representations for 'interpretation of surface features' showed highest frequency. For 'relatedness to text' criteria, 'completely related and linked' and 'completely related and unlinked' representations showed the highest frequency. It means that most representations were properly related with the text. There were appropriate captions for most representations. The degree of correlation between representations comprising a multiple one was largely sufficiently linked with regards to the criteria 'degree of correlation between representations comprising a multiple one'. The complete representations for 'function of representation' showed the highest frequency in the aggregate, however incomplete representations showed more frequencies in the inquiry parts. The typical representations for each achievement standard differed in terms of the type, contained information, used symbols and so on. The educational implications with the use of representations presented in seventh grade textbook were discussed.

• Journal of Aquaculture
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• v.11 no.1
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• pp.49-58
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• 1998

The spawning behavior and early life history of the Korean aucha perch, Coreoperca herzi were studied. The eggs were spawned in a one-layer mass, hanging from the underside of a largy stone and guarded by one male. According to the considerable size difference os eggs in the individual ovaries, it was concluded that they spawns several times within a spawning season of May~June. The ripe eggs were demersal and adhesive, and their diameter were 2.60~3.04mm with several oil globule of 0.10~0.64mm. Hatching in the tank with $19.0{\pm}1.0^{\circ}C.$ in men water temperature started from the 380 hours after fertilization. Newly-hatched larvae were measured 6.45~7.34mm in total length (TL, mean : 6.85mm), and mouth and anus were open. Melanophores were present on the head, around the yolk, and on the dorsal part of the abdominal region. 3 days old larvae were measured 7.00~7.40mm in TL (mean : 7.25mm), and they fed Daphnia sp. and Brachionus plicatilis actively. 6 days old larvae transformed to postlarval stage and they were 7.94~10.10mm in TL (mean : 9.00mm). As yolk sac were nearly absorbed, the caudal notochord flex at 45. Aggregate numbers of all fin rays were completed at over 16.90~19.80mm in TL (30 days after hatching), at which time the larvae reached the juvenile stage. In fifty days old larvae(24.60~27.10mm in TL) were similar in body form, lateral line and color to adult.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.2
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• pp.137-144
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• 2016

The aim of this study was to evaluate the effect of a range of acidic pH values on the push-out bond strength and surface morphology of tricalcium silicate materials: Biodentine$^{(R)}$, Theracal$^{(R)}$ and ProRoot MTA$^{(R)}$. The standardized lumens of root slices prepared from extracted single-root human teeth were filled with Biodentine$^{(R)}$, Theracal$^{(R)}$ and ProRoot MTA$^{(R)}$ according to manufacturer's instructions. The specimens were randomly divided into 4 groups (n = 20) for each material and then incubated for 4 days at $37^{\circ}C$; 3 acidic groups (butyric acid buffered at pH 4.4, 5.4, 6.4) and 1 control group (phosphate buffered saline solution at pH 7.4). The push-out bond strengths were then measured by using a universal testing machine and the surface morphology of each experimental group was analyzed by a scanning electron microscope. Biodentine$^{(R)}$ and Theracal$^{(R)}$ showed higher push-out bond strength compared with ProRoot MTA$^{(R)}$ after exposure to acidic pH values. A substantial change in the surface morphology of each material occurred after exposure to different pH values. In conclusion, the push-out bond strengths of Biodentine$^{(R)}$ and Theracal$^{(R)}$ are higher than the ProRoot MTA$^{(R)}$. Further the acidic environment weakens the push-out bond strength and microstructure of tricalcium silicate materials.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.2
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• pp.129-136
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• 2016

The purpose of this study is to examine the sealing effect and efficiency of root canal filling MTA (Endoseal, Endoseal MTA). A total of 106 extracted single rooted teeth were used and classified with group AH (AH-26), group PR (ProRoot MTA), group ES (Endoseal) and group EM (Endoseal MTA) depending on filled sealers. Time was measured in each group when sealers were filled. The groups were divided into subgroup A and subgroup B. The sealing of root canal walls and penetration of sealer in the dentinal tubule were evaluated, respectively. According to the results, the sealing of root canal walls and dentinal tubule penetration of root canal filling MTA were inferior to AH-26 (p < 0.05). When compared with ProRoot MTA, however, there was no significant difference in sealing of root canal walls (p > 0.05), but dentinal tubule penetration was high (p < 0.05). Working time was shorter in root canal filling MTA than ProRoot MTA and AH-26 (p < 0.05). In conclusion, root canal filling MTA has lower root canal sealing effect than resin-based sealer, however, when in MTA needed root canal filling, it could be an effective alternative.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.3
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• pp.229-236
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• 2011

ProRoot MTA(Dentsply Tulsa, U.S.A) which has similar component with Portland cement has setting expansion character and long setting time. Excessive expansion can cause fracture at the apical portion of the root and decreasing of volume stability. And the long setting time makes additional visits for crown restoration and slow setting process of this material can change physical properties itself. In this study, among requirements of root canal filling material(KS P ISO 6876) which is revised at 2008, we investigated the setting time and setting expansion. Objects are recently developed OrthoMTA(BioMTA, Korea), conventional ProRoot white MTA(Dentsply Tulsa, U.S.A) and White portland cement(Union, Korea). The results in setting expansion, OrthoMTA was $0.08{\pm}0.02%$, ProRoot white MTA and White portland cement were each $0.28{\pm}0.06$, $0.80{\pm}0.25%$(p<0.05). The results in setting time, OrthoMTA, ProRoot white MTA, White portland cement were each $307.78{\pm}3.83$ min, $150.44{\pm}2.35$ min, $235.33{\pm}9.07$ min(p<0.05).

• Journal of the Economic Geographical Society of Korea
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• v.16 no.2
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• pp.182-197
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• 2013

This paper deals with the relationship between cultural factor and economic factor in the spread of Hallyu(Korean Wave). To do so, the paper defines the traditional Hallyu items, drama and K-Pop, as 'cultural Hallyu' and other Popular industrial products such as electronics and mobile products as 'business Hallyu'. Based on this definition, the paper analyzes the relationship between the two Hallyu's in Thailand. The analysis has been conducted as follows. First, the paper describes the history of 'cultural Hallyu' and 'business Hallyu' in Thailand by reviewing their introduction and current situations in Thailand market. Secondly, using various aggregate data, the paper analyzes the causality of the two Hallyu's, focusing on the period of their Popularity and growth in Thailand. In addition to the macro-level analysis, the paper researched individual opinions of Thai people about the influence of Hallyu on the success of Korean companies, as well as about the influence of the Korean business companies on the success of Hallyu. This analysis has been conducted using the results of focus group discussion(FGD) of 17 Bangkok people. In both macro and individual level analyses, we found that the 'cultrual Hallyu' has influenced on the success of the 'business Hallyu' rather than vice versa. For further research, it is necessary to analyze the reciprocal influences and synergy effects between the 'cultural Hallyu' and 'business Hallyu'.

• Journal of Korean Society of Forest Science
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• v.105 no.2
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• pp.223-230
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• 2016

This study was carried out to investigate the quarrying and restoration characteristics on quarry in Korea. We researched quarrying and restoration status, analyzed the relationship between restoration area and permitted period, permitted area, quarrying volume, pit slope width, height, and berm width from 55 quarry sites. Most of the quarries were located in the following conditions : mixed forest, average altitude of less than 300 m, average mountain slope of $61^{\circ}$<, hillside, granite and landslide hazard class. Major quarrying characteristics were permitted period of 6~10 years, permitted area of less than 10 ha, quarrying volume of less than $1,000,000m^3$, a stone type of aggregate, a quarrying type of terrace, pit slope of $61^{\circ}$< Most quarries were restored by themselves, and the main restoration type was slope greening. Also, area ratio of flatland, pit slope, and berm was 54.9:39.6:5.5. Ccorrelation analysis showed that quarrying area was positively correlate with quarrying volume (${\alpha}=0.01$), permitted area, pit width, and pit height (a=0.05).

• Korean Journal of Ichthyology
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• v.12 no.4
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• pp.230-235
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• 2000

The purpose of the present study was to describe the morphological and skeletal development of the larvae and juvenile of Ilisha elongata(Bennett). The larvae(mean 5.02 mm in total length, TL) opened the mouth and anus with 36~38+15~16=51~54 myotomes, and anus located about 73.0% of TL. The clavicle of shoulder girdle was ossified. The larvae(mean 7.82 mm in TL) have all fin-fold differentiated and its caudal notochord began to flex. Parasphenoid of cranium and dentary of the lower jaw were ossified. The caudal notochord of the larva(mean 9.84 mm) was flexed $45^{\circ}$, and anus located about 67.0% of TL. The body height of the larvae(mean 23.32 mm in TL) were 18.0~20.0% of TL, and the aggregate numbers of all fin rays were completed. Ossification was completed in the larva of mean 26.52 mm in TL.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.1-11
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• 2020

As an important basic building block of the smart grid environment, smart meter provides real-time electricity consumption information to the utility. However, ensuring information security and privacy in the smart meter data aggregation process is a non-trivial task. Even though the secure data aggregation for the smart meter has been a lot of attention from both academic and industry researchers in recent years, most of these studies are not secure against internal attackers or cannot provide data integrity. Besides, their computation costs are not satisfactory because the bilinear pairing operation or the hash-to-point operation is performed at the smart meter system. Recently, blockchains or distributed ledgers are an emerging technology that has drawn considerable interest from energy supply firms, startups, technology developers, financial institutions, national governments and the academic community. In particular, blockchains are identified as having the potential to bring significant benefits and innovation for the electricity consumption network. This study suggests a distributed, privacy-preserving, and simple secure smart meter data aggregation system, backed up by Blockchain technology. Smart meter data are aggregated and verified by a hierarchical Merkle tree, in which the consensus protocol is supported by the practical Byzantine fault tolerance algorithm.