• Journal of The Korean Association For Science Education
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• v.22 no.4
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• pp.796-805
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• 2002

This study examined the knowledge structure constructed by children before formal instruction, and successive changes in the structural complexity of knowledge during and after the learning of 'Structure and Function of Plant' unit. It also investigated how those changes were affected by children's learning modes. The researchers made the 5th graders draw the first draft of their concept map to see the pre-existing knowledge structure concerned with the unit and four more concept maps after completing every fourth lesson. And to see how long their knowledge structures were preserved, the researchers made children draw additional concept maps in 3 days, 3 months, and 7 months after completing the unit. Children drew their current concept maps on the basis of the previous one while learning the unit and without the previous one after completing the unit. Each concept map drawn by children showed the degree of their current understanding on the structures and functions of plants. The results revealed that only two levels of hierarchy and five relationships among the components of the first concept map(relationship, hierarchy, cross link and example) were proven to be valid in terms of conceptual relevance. Growth in the structural complexity of knowledge took place progressively throughout the unit and the effects of learning mode on the growth were favorably reflected in concept map scores of meaningful learners over time(relationship, cross link, example: p<.01, hierarchy: p<.05). Although there were some differences on the concept map scores between two types of learners, they commonly showed that knowledge restructuring had occurred apparently in the early periods from the 1st to the 6th lesson and had not occurred at all in the last period of the unit. The frequency of tuning was higher in rote learners than in meaningful learners throughout the unit, but the frequency of accretion was reverse. Concept map scores of rote learners constructed in the course of learning of the unit decreased little by little gradually in all the categories after completing the unit. However, the average total map score of meaningful learners increased a little more in 7 months than in 3 months after completing the unit. Therefore it can be inferred that meaningful learners construct more stable and well-differentiated knowledge structures than the rote learners.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.791-806
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• 2020

In this study, a block shear strength test was conducted to compare and analyze the strength and failure mode on the glued laminated timber, CLT, and Ply-lam CLT, which are mainly used for the construction of wood construction as engineering wood. Through this, the Ply-lam CLT manufacturing conditions for optimum production, such as the type of lamina, plywood, adhesive, and layer composition, were investigated. The results are as follow. Through block shear strength test, it showed high strength in the order of glued laminated timber, Ply-lam CLT and CLT. In particular, the shear strength of Ply-lam CLT, which is made of a composite structure of larch plywood and larch lamina, passed 7.1 N/㎟, which is a Korean industrial standards for block shear strength of structural glued laminated timber. In addition, in this study, there was no different in shear strength according to the adhesive type used for glulam, CLT, and Ply-lam CLT adhesion. However, in the case of Ply-lam CLT, the difference in shear strength of Ply-lam CLT was shown according to the type of lamina and plywood. The results showed high strength in the order of Larix kaempferi > Mixed light hardwood ≒ Pinus densiflora, sieb, et, Zucc plywood. The optimal configuration of Ply-lam CLT is when larch plywood and larch lamina are used, and it is decided that the adhesive can be used by selecting PRF and PUR according to the application. The results of block shear strength failure mode by type of wood based materials were analyzed. The failure mode showed shear parallel-to-grain for glulam, rolling shear for CLT, and shear parallel-to-grain and rolling for ply-lam CLT. This is closely related to shear strength results and is decided to indicate higher shear strength in Ply-lam CLT than in CLT due to rolling shear.

• Journal of Intelligence and Information Systems
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• v.22 no.2
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• pp.57-79
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• 2016

It is a rising trend that the number of users using one of the social media channels, the Social Network Service, so called the SNS, is getting increased. As per to this social trend, more companies have interest in this networking platform and start to invest their funds in it. It has received much attention as a tool spreading and expanding the message that a company wants to deliver to its customers and has been recognized as an important channel in terms of the relationship marketing with them. The environment of media that is radically changing these days makes possible for companies to approach their customers in various ways. Particularly, the social network service, which has been developed rapidly, provides the environment that customers can freely talk about products. For companies, it also works as a channel that gives customized information to customers. To succeed in the online environment, companies need to not only build the relationship between companies and customers but focus on the relationship between customers as well. In response to the online environment with the continuous development of technology, companies have tirelessly made the novel marketing strategy. Especially, as the one-to-one marketing to customers become available, it is more important for companies to maintain the relationship marketing with their customers. Among many SNS, Facebook, which many companies use as a communication channel, provides a fan page service for each company that supports its business. Facebook fan page is the platform that the event, information and announcement can be shared with customers using texts, videos, and pictures. Companies open their own fan pages in order to inform their companies and businesses. Such page functions as the websites of companies and has a characteristic of their brand communities such as blogs as well. As Facebook has become the major communication medium with customers, companies recognize its importance as the effective marketing channel, but they still need to investigate their business performances by using Facebook. Although there are infinite potentials in Facebook fan page that even has a function as a community between users, which other platforms do not, it is incomplete to regard companies' Facebook fan pages as communities and analyze them. In this study, it explores the relationship among customers through the network of the Facebook fan page users. The previous studies on a company's Facebook fan page were focused on finding out the effective operational direction by analyzing the use state of the company. However, in this study, it draws out the structural variable of the network, which customer committment can be measured by applying the social network analysis methodology and investigates the influence of the structural characteristics of network on the business performance of companies in an empirical way. Through each company's Facebook fan page, the network of users who engaged in the communication with each company is exploited and it is the one-mode undirected binary network that respectively regards users and the relationship of them in terms of their marketing activities as the node and link. In this network, it draws out the structural variable of network that can explain the customer commitment, who pressed "like," made comments and shared the Facebook marketing message, of each company by calculating density, global clustering coefficient, mean geodesic distance, diameter. By exploiting companies' historical performance such as net income and Tobin's Q indicator as the result variables, this study investigates influence on companies' business performances. For this purpose, it collects the network data on the subjects of 54 companies among KOSPI-listed companies, which have posted more than 100 articles on their Facebook fan pages during the data collection period. Then it draws out the network indicator of each company. The indicator related to companies' performances is calculated, based on the posted value on DART website of the Financial Supervisory Service. From the academic perspective, this study suggests a new approach through the social network analysis methodology to researchers who attempt to study the business-purpose utilization of the social media channel. From the practical perspective, this study proposes the more substantive marketing performance measurements to companies performing marketing activities through the social media and it is expected that it will bring a foundation of establishing smart business strategies by using the network indicators.

• Applied Microscopy
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• v.36 no.1
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• pp.35-45
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• 2006

Plants of Vitex negundo are known to develop numerous trichomes throughout their body, where certain trichome types have been believed to be one of the plausible structures for the unique scents. In the current study. structural aspects of the trichomes have been examined in leaves and stems of Vitex negundo using TEM and SEM. Trichome types as well as structural changes that occurred in certain trichomes during secretion have been mainly focused. Three type of glandular trichomes and two types of non-glandular trichomes were developed in the epidermis of young and mature Vitex negundo plants. The glandular trichomes included the peltate type (Type 1), the capitate type (Type 2), and degraded capitate type (Type 3), whereas the non-glandular warty trichomes contained the multicellular (Types 4) and unicellular type (Type 5). Type 1 and 2 consisted of head and stalk cells, but their number and size were different. One secretory cavity was formed from the four head cells in the former, but only two head cells were involved in the latter. The cytoplasmic density in the head cell was quite high and in particular, sER and Golgi bodies were well developed. At initiation of their development, the cuticle layer of the head cells separated from the outer tangential wall to form a secretory cavity. Subsequently the cavity expanded acropetally and a large number of secretory vesicles continuously produced from the head cells until they filled the entire cavity. The cavity contained materials that would be soon discharged into intercellular spaces and/or into the air. The cavity began to decrease the volume by contracting at initial secretion but degrade rapidly within short time. It has been suggested that the mode of secretion in V. negundo is probably the eccrine secretion, since no break or rupture of the cavity has been observed during examination. Contrastingly Type 3 exhibited deterioration of the head cell at early stage. Type 4 was about $110{\sim}190{\mu}m$ long, consisting of $2{\sim}3$ cells, and distributed more in the adaxial epidermis compared to the abaxial surface. However, $20{\sim}30{\mu}m$ long Type 5 was extremely dense in both epidermis. Among several trichome types, Type 1 and 2 probably play an important role in discharging unique aromatic scents in plants of V. negundo.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.73-80
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• 2022

In this study, details of NRC beam-column connections were developed in which beam and columns pre-assembled in factories using steel angles were bolted on site. The developed joint details are NRC-J type and NRC-JD type. NRC-J type is a method of tensile joining with TS bolts to the side and lower surfaces of the side plate of the NRC column and the end plate of the NRC beam. NRC-JD type has a rigid joint with high-strength bolts between the NRC beam and the side of the NRC column for shear, and with lap splices of reinforcing bar penetrating the joint and the beam main reinforcement for bending. For the seismic performance evaluation of the joint, three specimens were tested: an NRC-J specimen and NRC-JD specimen with NRC beam-column joint details, and an RC-J specimen with RC beam-column joint detail. As a result of the repeated lateral load test, the final failure mode of all specimens was the bending fracture of the beam at the beam-column interface. Compared to the RC-J specimen, the maximum strength of the specimen by the positive force was 10.1% and 29.6% higher in the NRC-J specimen and the NRC-JD specimen, respectively. Both NRC joint details were evaluated to secure ductility of 0.03 rad or more, the minimum total inter-story displacement angle required for the composite intermediate moment frame according to the KDS standard (KDS 41 31 00). At the slope by relative storey displacemet of 5.7%, the NRC-J specimen and the NRC-JD specimen had about 34.8% and 61.1% greater cumulative energy dissipation capacity than the RC specimen. The experimental strength of the NRC beam-column connection was evaluated to be 30% to 53% greater than the theoretical strength according to the KDS standard formula, and the standard formula evaluated the joint performance as a safety side.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.897-905
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• 2013

In this study, sorption coefficients (${\log}K_{OC}$, n) for the binding of phenanthrene (PHE) to soil humins, insoluble fraction of soil humc substances (HS), were determined and relationship between the sorption coefficients and structural characteristics of the soil humins were investigated. The soil humins used in the present study were isolated from 7 different soils including 5 domestic soils, an IHSS standard and a peat soil, and characterized by elemental analysis and CPMAS $^{13}C$ NMR method. $^{13}C$ NMR spectral features indicate that the soil humins are mainly made up of aliphatic carbons (57.1~72.3% in total carbon) with high alkyl-C moiety, and the alkyl-C contents ($C_{Al-H,C}$, %) was in order of granite soil Hu (26~42%) > volcanic ash soil, HL Hu (23.9%) > Peat Hu (14.0%). The results of correlation study show that a positive relationship ($r^2$ = 0.77, p < 0.05) between organic carbon normalized-sorption coefficients ($K_{OC}$, mL/g) and alkyl-C contents($C_{Al-H,C}$, %), while negative relationship ($r^2$ = (-)0.74, p < 0.05) between Freundlich sorption parameter (n) and H,C-substituted aromatic carbon contents ($C_{Ar-H,C}$, %). The magnitude of $K_{OC}$ values are also negatively well correlated with polarity index (e.g., PI, N + O)/C) ($r^2$ = (-)0.74, p < 0.1). These results suggest that the binding capacity (e.g., $K_{OC}$) for PHE is increased in soil humin molecules having high contents of alkyl-C or lower polarity, and nonlinear sorption for PHE increased as the H,C-substituted aromatic carbon contents ($C_{Ar-H,C}$, %) in the soil humins increased. The PHE sorption characteristics on soil humins are discussed based on the dual reactive mode of sorption model.

• The Journal of the Petrological Society of Korea
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• v.19 no.1
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• pp.31-49
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• 2010

Nearly NS-trending Fe-Ti ore bodies intermittently occur in the Hadong anorthosites, south Korea, irrespective of the rock types of the anorthosites. In order to determine their occurrence mode and deformation history, we collected the features of occurrence and geological structures in the field, petrographic features using thin sections of the principal constituent rocks, and geochemical data of ilmenites in the ore body using electron probe microanalysis. Fe-Ti ore bodies examined in this study are divided into two types: dike- and lamina-types. It is steadily supported that the dike-type has intruded into the anorthositic rocks after their emplacement and solidification. And the laminar-type is probably a result of the mylonitization and transposition of the dike-type ore bodies parallel to the shear planes, due to later strong dextral ductile shearing. In the meantime, the Fe-Ti ore bodies have experienced the stronger dextral shearing in the more northern part of the study area, i.e. Cheongryong-ri, Wolhoeng-ri, Jonghwa-ri, and Jayangri and Baekun-ri in ascending order of its strength, together with the less content of $TiO_2$. All ilmenites of the ore bodies have very similar chemical composition, as pure ilmenite of 52~55 wt.% in $TiO_2$ content, irrespective of the occurrence mode and degree of later ductile shearing of the ore bodies. And they didn't experience to exsolve into magnetite. The structural data indicate that the Hadong anorthosites have deformed by NNE-trending folding, intrusion of the Fe-Ti ore bodies, NNW~NNE-trending dextral ductile shearing, NW~NNW-trending sinistral semi-brittle shearing, and intrusion of NNE~NE-trending mafic dykes in descending order of chronology after the formation of foliation of the anorthositic rocks. The foliation is interpreted as a result of the accumulation of crystals that settle out from the magma by the action of gravity.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.451-464
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• 2022

The high-level nuclear waste repository is a deep geological disposal system exposed to complex environmental conditions such as high temperature, radiation, and ground-water due to handling spent nuclear fuel. Continuous exposure can lead to cracking and deterioration of the structure over time. On the other hand, the high-level nuclear waste repository requires an ultra-long life expectancy. Thus long-term structural health monitoring is essential. Various sensors such as an accelerometer, earth pressure gauge, and displacement meter can be used to monitor the health of a structure, and a piezoelectric sensor is generally used. Therefore, it is necessary to develop a highly durable sensor based on the durability assessment of the piezoelectric sensor. This study designed an accelerated life test for durability assessment and life prediction of the piezoelectric sensor. Based on the literature review, the number of accelerated stress levels for a single stress factor, and the number of samples for each level were selected. The failure mode and mechanism of the piezoelectric sensor that can occur in the environmental conditions of the high-level waste repository were analyzed. In addition, two methods were proposed to investigate the maximum harsh condition for the temperature stress factor. The reliable operating limit of the piezoelectric sensor was derived, and a reasonable accelerated stress level was set for the accelerated life test. The suggested methods contain economical and practical ideas and can be widely used in designing accelerated life tests of piezoelectric sensors.

• Journal of Korean Society of Steel Construction
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• v.22 no.5
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• pp.477-485
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• 2010

Various monitoring sensors are used to predict and detect structural damage. Smart sensors, such as glass-fiber sensors, PZT, and MEMS, among others, have replaced traditional sensors. They are now being used in many areas. This study aims to predict the damage by measuring the PZT voltage attached on the specimen by the applied impact load. In the experiment to detect damages in beam connection, simple $H-400{\times}200{\times}8{\times}13$ beams were spliced with bolts. The results of FFT between PZT sensor and accelrometer were compared to measure the sensitivity of the PZT sensor. The damage to the beam was presumed by loosening the bolt, and then the damage measurement was accompanied. Secondly, a steel $PL600{\times}65{\times}5.8$ plate beam was fabricated for the purpose of experimenting on damage measurement. Impact loading test on three different locations was carried out. Damage width varied between 6~42mm on both sides by cutting, using a steel saw. The ratio of frequencies before and after the damage was computed to quantify the damage level by using FFT, and the change in mode pattern with the increased damage was investigated to measure the damage.

• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.345-351
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• 2017

This study evaluated the effectiveness of V-shaped ties as an alternative to the supplementary crossties specified in ACI 318-14 on the flexural ductility of reinforced concrete columns. From column specimens tested under constant axial loads and reversed cyclic lateral loads, the mode of failure and lateral load-lateral displacement relationship were measured according to the variation of the applied axial load levels. After the columns reached the peak lateral load capacity, the $90^{\circ}$ hooks of the crossties gradually opened, which eventually caused premature buckling of the longitudinal reinforcement and severe crushing of the core concrete, whereas no V-ties were extracted from the core concrete until the column failure. As a result, the cumulative work damage indicators up to 80% of the peak lateral load for V-tie columns under the axial load level of 0.2, 0.4, and 0.55 was as much as 2.4, 2.3, and 5.2 times higher, respectively, than those of the companion crosstie columns. The superiority of the V-ties to the conventional crossties in enhancing the flexural ductility of columns became more prominent as the axial load level increases.