• Advances in biomechanics and applications
• /
• v.1 no.4
• /
• pp.227-237
• /
• 2014

The in vitro construction of osteo-articular large implants combining biomaterials and cells is of great interest since these tissues have limited regeneration capability. But the development of such organoids is particularly challenging, especially in the later time of the culture, when the extracellular matrix has almost filled the initial porous network. The fluid flow needed to efficiently perfuse the sample can then not be achieved using only the hydraulic driving force. In this paper, we investigate the interest of using an electric field to promote mass transport through the scaffold at the late stage of the culture. Based on the resolution of the electrokinetics equations, this study provides an estimation of the necessary electric driving force to reach a sufficient oxygen perfusion through the sample, thus analyzing the feasibility of this concept. The possible consequences of such electric fields on cellular activities are then discussed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.41 no.3
• /
• pp.305-316
• /
• 2021

Construction accidents occur due to a number of reasons-worker carelessness, non-adoption of safety equipment, and failure to comply with safety rules are some examples. Because much construction work is done outdoors, weather conditions can also be a factor in accidents. Past construction accident data are useful for accident prevention, but since construction accident data are often in a text format consisting of natural language, extracting construction hazards from construction accident data can take a lot of time and that entails extra cost. Therefore, in this study, we extracted construction hazards from 2,026 domestic construction accident reports using text mining and performed a seasonal analysis of construction hazards through frequency analysis and centrality analysis. Of the 254 construction hazards defined by Korea's Ministry of Land, Infrastructure, and Transport, we extracted 51 risk factors from the construction accident data. The results showed that a significant hazard was "Formwork" in spring and autumn, "Scaffold" in summer, and "Crane" in winter. The proposed method would enable construction safety managers to prepare better safety measures against outdoor construction accidents according to weather, season, and climate.

• 한국문화재보존과학회:학술대회논문집
• /
• 2002.02a
• /
• pp.21-31
• /
• 2002

Lime-soil consolidations are very important as structural material, bonding material, waterproofing material, and finishing material in korea traditional buildings. In this study, we investigated site application trouble in korea traditional buildings being repaired or restored, and propose following solutions. 1) To diminish quality variation occurred by slaking quick-lime in site, it is desirable to use slaked-lime for lime-soil consolidation. 2) For uniform construction of lime-soil consolidation, we would recommend builders to use mixer to be uniform mixture, premixed type materials and compacting machine in field, 3) and to use rigid suitable temporary construction as scaffold for preventing traditional buildings from additional damage occurred in demolition and construction of a layer of lime-soil consolidation of a roofing. 4) For suitable repair of traditional buildings, it is necessary to specify definitely materials and construction methods suggested by the standard specifications for repair of the cultural property.

• Safety and Health at Work
• /
• v.9 no.2
• /
• pp.184-191
• /
• 2018

Background: Due to an increasing number of workers aged 50 years and above, the number of those employed is also on the rise, and those workers aged 50 and over has exceeded 50% of the total fatal occupational injuries. Therefore, it is necessary to implement the selection and concentration by identifying the characteristics of high-risk groups necessary for an effective prevention against and reduction of fatal occupational injuries. Methods: This study analyzed the characteristics of high-risk groups and the occupational injury fatality rate per 10,000 workers among the workers aged 50 and over through a multi-dimensional analysis by sex, employment status of workers, industry and occupation by targeting 4,079 persons who died in fatal occupational injuries from January 2007 to December 12. Results: The share of the workers aged 50 years and above is increasing every year in the total fatal occupational injuries occurrence, and the high-risk groups include 'male workers' by sex, 'daily workers' by worker's status, 'craft and related-trades workers' by occupation, and 'mining' by industry. Conclusion: The most frequent causal objects of fatal occupational injuries of the workers aged 50 years and above are found out to be 'installment and dismantlement of temporary equipment and material on work platforms including scaffold' in the construction industry and 'mobile crane, conveyor belt and fork lifts' in the manufacturing industry.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.9
• /
• pp.121-126
• /
• 2019

Despite the trend of decreasing accidents, falling accidents in the construction industry have not decreased and are even rising. Most major accidents are falling accidents caused by hanging scaffolding and are mostly serious. We conducted a review of the literature, institutions, and regulations, which showed that domestic standards are not unified because they are drawn up by referring to overseas standards for hanging scaffolding. New regulations or standards should be established, which should reflect the safety plans for equipment, work advance plans, education, and management. If facility improvement plan for Hanging Scaffolding and implementation of revision of the current work use, regulations and guides are implemented, it will be recognized in advance of the causes of the accident statistics and the classification system and will be the basis for the implementation of joint efforts by workers, managers, supervisors and owners to reduce accidents.

• Steel and Composite Structures
• /
• v.43 no.1
• /
• pp.91-106
• /
• 2022

This paper has focused on presenting a three dimensional theory of elasticity for free vibration of 3D-graphene foam reinforced polymer matrix composites (GrF-PMC) cylindrical panels resting on two-parameter elastic foundations. The elastic foundation is considered as a Pasternak model with adding a Shear layer to the Winkler model. The porous graphene foams possessing 3D scaffold structures have been introduced into polymers for enhancing the overall stiffness of the composite structure. Also, 3D graphene foams can distribute uniformly or non-uniformly in the shell thickness direction. The effective Young's modulus, mass density and Poisson's ratio are predicted by the rule of mixture. Three complicated equations of motion for the panel under consideration are semi-analytically solved by using 2-D differential quadrature method. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary at the curved edges. It is explicated that 3D-GrF skeleton type and weight fraction can significantly affect the vibrational characteristics of GrF-PMC panel resting on two-parameter elastic foundations.

• Journal of the Korea Institute of Construction Safety
• /
• v.2 no.1
• /
• pp.28-35
• /
• 2019

The average number of deaths in the construction industry reaches 500 per year, and in particular, it is confirmed that the type of accidents and deaths caused by disasters such as work platforms has occupied more than 60% of the total. In this study, we presented a structured and combined solution for technology, management, education, and cost that can solve systematically, politically, and external environmental factors as well as direct influence factors. In addition, we examined the safety and safety standards of domestic and international safety, and discussed implications. First, direct impact factors, organizational impact factors, policy influence factors, and external environmental impact factors were examined and classified into technical, education, and institutional dimensions. Second, in relation to the installation of the work scaffold, the standards (OSHA 1926.452), UK (The Work at Height Regulations 2005 No.735, BS5975), Japan (Labor Safety and Sanitation Regulations) and Germany (DIN 4420_4, DIN EN12810). In the case of domestic safety standards, similar to the foreign safety standards, safety measures such as materials and specifications are applied. However, details related to the installation, assembly and structure of the work platform are somewhat different from those in the United States and the United Kingdom excluding Japan. Using the results of this study, it is possible to understand the cause of the accident of foot pedestrian accident more systematically and comprehensively, and safety managers and researchers are expected to help in the accident investigation.

• Journal of Educational Research in Mathematics
• /
• v.9 no.1
• /
• pp.263-278
• /
• 1999

Computer with various powerful functions has profound potential for mathematics instruction and learning. As computer technology progress, its applicability to mathematics education become more comprehensive. Not only its functional development but various psychological positions also changed the way computer technology utilized in mathematics education. In behaviorist's perspective, computer viewed as a teaching machine and constructivist viewed computer as microworld where students could explore various mathematical contents. Both theoretical positions emphasized individual aspect of learning because behaviorist tried to individualize learning using computer and constructivist focused on the process of individual construction. But learning is not only a individual event but also a social event. Therefore we must take social aspect into account. This is especially important when it comes to computer based learning. So far, mathematics loaming with computer weighed individual aspect of loaming. Even in microworld environment, learning should be mediated by teacher and collaborative learning activities. In this aspect, the roles of teacher and peers are very important and socio-cultural perspective sheds light on the computer based learning. In socio-cultural perspective, the idea of scaffold is very important in learning and students gradually internalize the social dimension and scaffolding is gradually faded. And in the zone of proximal development, teacher and more competent peers guide students to formulate their own understanding. In sum, we must take following points into account. First of all, computer should not be viewed as a medium for individualized teaming. That is, interaction with computer should be catalyst for collaborative activities with peers. So, exploration in computer environment has to be followed by small group activities including small group discussion. Secondly, regardless of the role that computer would play, teacher should play a crucial role in computer based learning. This does not mean teacher should direct every steps in learning process. Teacher's intervention should help student construct actively. Thirdly, it is needed to conceptualize computer in learning situation as medium. This would affect learning situation and result in the change of pre-service and in-service teacher training. Computer to be used effectively in mathematics classroom, researches on assessment of computer based learning are needed.

• Macromolecular Research
• /
• v.16 no.8
• /
• pp.704-710
• /
• 2008

Injectable hydrogels are quite promising materials due to their potential to minimize invasive implantation and this provides versatile fitness irrespective of the damaged regions and facilitates the incorporation of bioactive agents or cells. In situ gel formation through stereocomplex formation is a promising candidate for injectable hydrogels. In this paper, a new series of enantiomeric, four-arm, PEG-PLA block copolymers and their stereocomplexed hydrogels were prepared by bulk ring-opening polymerization of D-lactide and L-lactide, respectively, with stannous octoate as a catalyst. The prepared polymers were characterized by $^1H$ nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT IR) spectroscopy, gel permeation chromatography (GPC) and thermal gravitational analysis (TGA), confirming the tailored structure and chain lengths. The swelling and degradation behavior of the hydrogels formed from a selected copolymer series were observed in different concentrations. The degradation rate decreased with increasing polymer content in the solution. The rheological behavior indicated that the prepared hydrogel underwent in situ gelation and had favorable mechanical strength. In addition, its feasibility as an injectable scaffold was evaluated using a media dependence test for cell culture. A Tris solution was more favorable for in situ gel formation than PBS and DMEM solutions were. These results demonstrated the in situ formation of hydrogel through the construction of a stereocomplex with enantiomeric, 4-arm, PEG-PLA copolymers. Overall, enantiomeric, 4-arm, PEG-PLA copolymers are a new species of stereocomplexed hydrogels that are suitable for further research into injectable hydrogels.

• Korean Journal of Breeding Science
• /
• v.50 no.4
• /
• pp.434-441
• /
• 2018

High-density genetic linkage mapping is critical for undertaking marker-assisted selection and confirming quantitative trait loci, as well as helping to build pseudomolecules of genomes. We constructed a genetic map using 94 $F_1$ populations generated from the interspecific cross between Korean cultivar "Wonwhang" (Pyrus pyrifolia, NCBI BioSample SAMN05196235) and European cultivar "Bartlett" (Pyrus communis). We designed a total of 24,267 SSR markers based on the genome sequences of "Wonwhang" for this. To select the markers that are linked to the traits important in pear breeding programs, SSR-containing genomic sequences were subjected to nucleotide sequence homology searches, which resulted in 510 SSR markers with high similarity to genes encoding proteins with putative functions such as transcription factors, resistance proteins, flowering time, and regulatory genes. Of these, 70 markers showed polymorphisms in parents and segregating populations and were used to construct a genetic linkage map, together with the unpublished 579 SNPs obtained from genotyping by sequencing analysis. The genetic linkage map covered 3,784.2 cM and the average distance between adjacent markers was 5.8 cM. Seventy SSR markers were distributed across 17 chromosomes with more than one locus.