• Composites Research
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• v.30 no.3
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• pp.169-174
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• 2017

Demand of glass fiber reinforced composites (GFRC) increased with developing aircraft and defense industries using resin transfer molding (RTM) process to produce complex product. In this research, wetting, interfacial, and mechanical properties were evaluated with different Cross-linking Density by Molecular Weight of Hardener. Epoxy resin as matrices was used bisphenol-A type and amine-type hardeners with different molecular weight. Specimens were manufactured via RTM and wetting property of resin and glass fiber (GF) mat was evaluated to viscosity of epoxy and injection time of epoxy matrix. Mechanical property of GFRC was determined via flexural strength whereas interfacial properties were determined by interlaminar shear strength (ILSS) and interfacial shear strength (IFSS). The difference in mechanical property depends upon the fiber weight fraction (wt %) of GFRC by RTM as well as the different Molecular Weight of Hardener.

• Wind and Structures
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• v.31 no.2
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• pp.103-142
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• 2020

One of the next frontiers in structural wind engineering is the design of tall buildings using performance-based approaches. Currently, tall buildings are being designed using provisions in the building codes and standards to meet an acceptable level of public safety and serviceability. However, recent studies in wind and earthquake engineering have highlighted the conceptual and practical limitations of the code-oriented design methods. Performance-based wind design (PBWD) is the logical extension of the current wind design approaches to overcome these limitations. Towards the development of PBWD, in this paper, we systematically review the advances made in this field, highlight the research gaps, and provide a basis for future research. Initially, the anatomy of the Wind Loading Chain is presented, in which emphasis was given to the early works of Alan G. Davenport. Next, the current state of practice to design tall buildings for wind load is presented, and its limitations are highlighted. Following this, we critically review the state of development of PBWD. Our review on PBWD covers the existing design frameworks and studies conducted on the nonlinear response of structures under wind loads. Thereafter, to provide a basis for future research, the nonlinear response of simple yielding systems under long-duration turbulent wind loads is studied in two phases. The first phase investigates the issue of damage accumulation in conventional structural systems characterized by elastic-plastic, bilinear, pinching, degrading, and deteriorating hysteretic models. The second phase introduces methods to develop new performance objectives for PBWD based on joint peak and residual deformation demands. In this context, the utility of multi-variate demand modeling using copulas and kernel density estimation techniques is presented. This paper also presents joined fragility curves based on the results of incremental dynamic analysis. Subsequently, the efficiency of tuned mass dampers and self-centering systems in controlling the accumulation of damage in wind-excited structural systems are investigated. The role and the need for explicit modeling of uncertainties in PBWD are also discussed with a case study example. Lastly, two unified PBWD frameworks are proposed by adapting and revisiting the Wind Loading Chain. This paper concludes with a summary and a proposal for future research.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.629-634
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• 2017

In the case of the UHP (Ultra high performance) tire that the demand has increased rapidly, compared with the commonly used tire, severe deformation has been observed because of the low aspect ratio. When repeated deformations are applied to the sidewall rubber, accumulated fatigue damage may cause fatigue failure. Thus, the evaluation of the durability of the tire sidewall rubber has become a very important issue to prevent accidents that occur while the vehicle is running. However, the research and design criteria for the durability performance of the tire sidewall rubber hardly exist. In this study, we suggest a lifetime prediction formula using strain energy density obtained by performing tensile tests and fatigue tests on two different kinds of the tire sidewall compounds. Additionally, the applicability of our findings for low fuel consumption tires was reviewed by converting the fatigue life of the sidewall rubber into the expected mileage of the tire.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.3
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• pp.107-112
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• 2014

In keeping with the increasing demand for medical services in accordance with the economic development, the use of oriental medicine is on the rise year by year. In particular, it is a tendency that the elderly over age 65 prefer the oriental medicine to the western medicine in Korea. Under the circumstance, changing into an aging society, the importance of oriental medical services has been growing. In this regard, this study evaluated the quality of medical services by conducting the density analysis and the accessibility analysis of oriental medical clinic targeting Jinju, which is one of local small and medium-sized cities. The study results reveal that oriental medical hospitals accounted for 27% of the entire medical facilities in Jinju, and there was an imbalance in the quality of the oriental medical services according to districts(called dong) because oriental medical hospitals were mainly concentrated in the central commercial areas. In particular, in terms of the analysis on the accessibility of an aging population over age 65 to the oriental medical hospitals, over 50% of the whole districts (dongs) in Jinju were blind spots in medical services, showing a very vulnerable condition. Accordingly, it is judged that systematic measures for improvement in support of the oriental medical services in local small and medium-sized cities should be provided in Korea when we consider the characteristics of Korea where an aging population is rapidly increasing.

• Science of Emotion and Sensibility
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• v.14 no.1
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• pp.165-174
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• 2011

Recent years have witnessed that IT-convergence technology has become the most important issue in the global market. Along with this trend, demand for PSS(i.e., Product-Service Systems) design has been rapidly increased in the smart clothing market. A case of the PSS design research, this study aimed to identify optimum conditions for weaving of POF-based flexible textile display(abbreviated as "PFTD") for mountaineer wear with safe-guard function regarding luminescent properties. Based on the findings regarding the optimum weaving condition of PFTD, several designs of mountaineer wear were suggested in this study. A total of 15 PFTD samples were prepared under various weaving conditions of weave structures and density of POF, and the luminance values of each sample were measured. As the results, the types of PFTD with structures and density of 'satin 3:1', 'satin 2:1', 'twill 3:1' and 'twill 2:1' indicated relatively higher luminescence. And based on the results and recent sports fashion trends, two suited mountaineering wears applying PFTD were illustrated in this study.

• Journal of Aquaculture
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• v.16 no.3
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• pp.159-164
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• 2003

Effect of the benthic echiurid Urechis unicinctus juveniles on the chemical characteristics of organically enriched sediment, as well as the individual survival rate and growth in various sediments, was investigated in this study to ascertain the effectiveness of U. unicinctus in the bioremediation of organically polluted sediment. The content of acid volatile sulfide (AVS) in the sediment of three coastal areas was 0.4±0.1 mg/gㆍdry sediment in Seonso, 0.1±0.01 mg/gㆍdry sediment in Myo-do, 0.02±0.01 mg/gㆍdry sediment in Dolsan-do, respectively. 500 juveniles with average body length of 1.2±0.3 mm were bred in these sediments. After 30 days, the AVS content of three places decreased to 0.29±0.3, 0.08±0.01 and 0.0l±0.01 mg/gㆍdry. After 60 days, the content was 0.23±0.03, 0.0l±0.01, 0.0l±0.01 mg/gㆍdry. The AVS content in the control (sediment from Seonso without juveniles) was 0.39±0.75 mg/gㆍdry sediment (after 30 days) and 0.45±0.01 mg/gㆍdry sediment (after 60 days). At the same time, the chemical oxygen demand (COD) and total ingition loss (TIL) of these sediments showed the same trend with that of AVS. Furthermore, 60 days later, the survival rate and growth of juveniles were 71.2%, 11.1±l.0 mm in Seonso, 89.8%, 12.0±1.3 mm in Myo-do and 81.6%, 11.9±1.9 mm in Dolsan-do. It was suggested that U. unicinctus can survive better in less polluted environment. Under different U. unicinctus juvenile density (100, 300, 500, 700, 900 individuals), after 60 days cultivation, the AVS content decreased from 0.4±0.1, 0.4±0.1, 0.4±0.3, 0.4±0.3, 0.4±0.3 mg/gㆍdry to 0.4±0.2, 0.3±0.2, 0.2±0.1, 0.2±0.1, 0.2±0.1 mg/gㆍdry. Therefore, the higher the density of juveniles, the greater the effect in improving the sediment. In comparison to different initial AVS concentration (0.40±0.01, 0.35±0.01, [I can't find a reference to this number above], 0.29±0.02, [I can't find a reference to this number above], 0.18±0.03, [I can't find a reference to this number above], 0.06±0.02 mg/gㆍdry sediment [I can't find a reference to this number above] and the control 0.0±0.0[I can't find a reference to this number above]), after 30 days cultivation with 500 juveniles, the AVS content was 0.29±0.03, 0.19±0.0, 0.15±0.01, 0.12±0.02, 0.05±0.0mg/gㆍdry and 0(control). After 60 days cultivation, the content was 0.23±0.03, 0.12±0.4, 0.10±0.01, 0.18±0.03, 0.06±0.02 mg/gㆍdry and 0 (control). Use % decrease in AVS content to state: The impact of U. unicinctus on the sediments was greater with higher concentrations of AVS. The results of this study indicate that U. unicinctus is effective in the biological treatment of sediments polluted by AVS and other organics.

• Journal of Surface Science and Engineering
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• v.49 no.2
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• pp.166-171
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• 2016

Cathodic protection is widely recognized as the most cost effective and technically appropriate corrosion prevention methodology for the port, offshore structures, ships. When applying the cathodic protection method to metal facilities in seawater, on the surface of the metal facilities a compound of calcium carbonate($CaCO_3$) or magnesium hydroxide($Mg(OH)_2$) films are formed by $Ca^{2+}$ and $Mg^{2+}$ ions among the many ionic components dissolving in the seawater. And calcareous deposit films such as $CaCO_3$ and $Mg(OH)_2$ etc. are formed by the surface of the steel product. These calcareous deposit film functions as a barrier against the corrosive environment, leading to a decrease in current demand. On the other hand, the general calcareous deposit film is a compound like ceramics. Therefore, there may be some problems such as weaker adhesive power and the longer time of film formation uniting with the base metal. In this study, we tried to determine and control the optimal condition through applying the principle of cathodic current process to form calcareous deposit film of uniform and compact on steel plate. The quantity of precipitates was analyzed, and both the morphology, component and crystal structure were analyzed as well through SEM, EDS and XRD. And based on the previous analysis, it was elucidated mechanism of calcareous deposit film formed in the sacrificial anode type (Al, Zn) and current density (1, 3, $5A/m^2$) conditions. In addition, the taping test was performed to evaluate the adhesion.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.295-306
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• 2004

Spatial patterns in the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike and environmental variables were examined in August 2001, In total, 156 macrobenthic species(123 intertidal species and 90 subtidal species) were recorded during this study, predominately polychaetes $(40{\%})$, bivalves $(22{\%})$, and crustaceans $(22{\%})$. Polychaetes made up less than $40{\%}$ of the intertidal communitr, but more than $50{\%}$ of the subtidal community. The mean density during this study was $1,456ind./m^{2}.$ Multivariate analysis (multidimensional scaling) revealed significant differences in community structure among four regions: near the Iwon dike (B1), the high and middle intertidal zone (B2), low intertidal zone (Al), and subtidal zone (A2). The number of species, total density, and diversity (H') varied significantly among the four regions. The distribution of macrobenthic community was affected by environmental variables, such as ${\%}$ silt/clay content, total sulfide, lose of ignition, and chemical oxygen demand. These environmental variables were negatively correlated with the dominant species (Nephtys polybranchia, Umbonium thomasi, and Scoloplos armiger) in the intertidal area, but positively correlated with the dominant species (Lumbrineris cruzensis, Notomastus latericeus, and Moerella sp.) in the subtidal area. Environmental variables $({\%}\;silt/clay content and total sulfide)$ were positively correlated with the dominant species (Heteromastus filiformis) in region Bl, but negatively correlated with the dominant species (Umbonium thomasi and Scoloplos koreanus) in region B2. Amphipods Urothoe spp. and Monoculodes koreanus were the dominant species in region Al. Umbonium thomasi, the dominant species in region B2, was not found in regions Bl or Al. We suggest that the inter-specific competition for territory and exposure to seawater may be important factors controlling the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike.

• Journal of Korea Society of Industrial Information Systems
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• v.24 no.2
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• pp.57-63
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• 2019

In order to facilitate the supply of gradually increasing power demand, it is also necessary to increase the number of power cables for power transmission as well as generation facilities. However, the expansion of electric power cables for supplying power to most urban areas requires a space for installation of additional cables, and the space for installing cables in domestic downtown areas is insufficient at present. The superconducting power cable, which can transmit more power with the same size, has emerged as an alternative to overcome the insufficient cable installation space. However, superconducting power cables, which have the advantage of large power transmission, have some losses in the AC (Alternating Current) system. Therefore, the design and analysis of AC losses are essential to introduce superconducting power cables in AC power transmission systems. In this paper, we analyze the AC loss of various superconducting power cables and consider the actual superconducting power cables and their application to the system. Although there is a theoretical calculation method of AC loss for single superconducting wire, it is not easy to calculate AC loss of superconducting power cable with large number. Therefore, the authors intend to analyze various kinds of superconducting power cable AC loss by using electromagnetic finite element analysis considering E-J (Electric field-Current density) characteristics of superconductivity. The analysis of the AC loss characteristics of the superconducting power cable will be an important factor in the design and development of the superconducting power cable to be applied to the actual system.

• Journal of radiological science and technology
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• v.46 no.1
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• pp.1-8
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• 2023

As the demand for bone mineral density testing increases in Korea, which is close to an aging society, it is necessary to evaluate the repeatability of equipment such as femur phantom other than l-spine for more accurate diagnosis. However, in clinical practice, it is often not possible to proceed such evaluation due to insufficient quality control conditions. Therefore, this study is to evaluate the usefulness of the femur phantom after fabricating the same using 3D printing technology. The femur phantom was output using GlowFill filament and FDM 3D printing type. Each phantom was repeatedly scaned 20 times to compare whether the existing l-spine phantom and the fabricated femur phantom were suitable as a phantom for quality control. Each time the seven researchers took three times, the location of the femur phantom was readjusted, and then scanned to confirm the error between the researchers. As a result of conducting repeatability evaluation using femur phantom, the coefficient of variation rate was 2%, which was within the minimum precision tolerance of 2.5%. The reproducibility between the researcher was also found to be suitable as the average coefficient of variation was 0.031 and the coefficient of variation rate was 3.1%, which was within the minimum precision error range of 5%. In conclusion, it is considered that the prospective attitude and usefulness of the femur phantom fabricated by 3D printing in clinical practice will be sufficient.