• Journal of Conservation Science
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• v.35 no.4
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• pp.317-329
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• 2019

Slag was collected from the iron-producing furnace site in Saengsoegol, Baegun mountain, where iron was manufactured by a righteous army against Japan in the Gwangyang region; then, the iron-manufacturing technique of the early modern period was investigated through scientific analysis. In the microstructure analysis results of the selected samples, iron bloom was mainly observed together with magnetite and fayalite. In the component analysis results of the compounds, it was confirmed that the furnace was built by using gangue of alkali feldspar or plagioclase series, and the ironmaking work was performed at a high temperature of at least 1050℃, because mullite was identified together with cristobalite and hercynite. Based on the chemical composition, it was speculated that low-grade iron ores were used as raw materials, and it seemed that the yield was low, because the total Fe content of the smelting slag samples was 37.72-49.93%. It was difficult to confirm whether a slag former was used, and it seemed that materials easily obtained nearby were used when the furnace was built, without considering the corrosion resistance. It appeared that the ironmaking work was performed at the Gwangyang Saengsoegol iron-producing furnace based on the direct ironmaking method in an environment that could escape the vigilance of the Japanese Empire to produce weapons that would be used for the resistance against Japan. It seemed that there was neither an advanced ironware production system nor a mass production system, and small-scale works were performed in short periods of time.

• Advances in concrete construction
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• v.10 no.5
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• pp.393-402
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• 2020

The given research focuses on examining the effect of relatively humidity (RH) and curing temperature on the hydrates as well as the porosity of calcium sulfoaluminate (CSA) cement pastes. Numerous tests, which consist of mercury intrusion porosimetry (MIP), thermosgravi metric (TG) and X-ray diffraction (XRD) were conducted. Various characterization techniques which include, scanning electron microscopy, Fourier transform microscopy along with X-ray diffraction evaluations were conducted on the samples to examine phase formation and crystallinity, morphology and microstructure along with bond formations and functional groups, respectively. During long-term study, the performance of concrete which consisted of limestone and flash-calcined was close to those from standard Portland cement concrete. Traditional classifications and methods of corrosion were widely used for the assessment of steel in concrete which may get employed to concrete which contains LC3 to recalibrate the range of polarization resistance for passitivity condition. For example, there is up to 79.5% and 146% respective flexural and compressive strengths. Moreover, they developed more advance electrical and thermo-mechanical performance with a substantial reduction in absorption of water of close to 400%. These advantages allow this research crucial to evaluate how these methods can be applied. Additionally, the research evaluates developed and more advanced cement preservation and repair techniques. The conclusion suggests concerted efforts by various stakeholders such as policy makers to enable low-carbon rates.

• Journal of Power System Engineering
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• v.13 no.3
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• pp.33-39
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• 2009

The aim of this study is to analyze the welds characteristics of the 205 stainless steel pipe for application of street pole material. The welds corrosion behavior of STS 205 pipe in 0.1 N sulphuric acid solution and 5% NaCl solution at room temperature was studied using both salt spray test and potentiodynamic polarization experiment. The morphology and components of corrosion products on surface of STS 205 pipe welds were investigated using SEM/EDX. The tensile strength and yield strength values of STS 205 plate were 715 MPa and 369 MPa respectively. The microvickers hardness values of STS 205 pipe welds were slightly increased than that of STS 304 pipe welds. Corrosion current density($I_{corr.}$) and critical current density($I_{crit.}$) values of STS 205 pipe welds in 3.5% NaCl solution were $1.89{\times}10^{-6}$ $A/cm^2$ and $15.8{\times}10 ^{-6}$ $A/cm^2$. The corrosion resistance of SIS 205 pipe welds was similar to its STS 304 pipe welds. The STS 205 and 304 pipe welds passive films were chromium oxide. Especially, the STS 205 pipe welds showed good corrosion resistance in 0.1 N sulphuric acid. This is attributed to the forming of protective chromium oxide on the surface of STS 205 pipe welds.

• International Journal of Highway Engineering
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• v.15 no.4
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• pp.107-116
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• 2013

PURPOSES: The liquid-type chemical warm-mix asphalt (WMA) additive has been developed. This study evaluates the basic properties of the additive and the mechanical properties of WMA asphalt and mixture manufactured by using the newly developed chemical additive. METHODS: First, the newly developed WMA additive was applied to the original asphalt by various composition of additive components and dosage ratio of additive. These WMA asphalt binders were evaluated in terms of penetration, softening point, rotational viscosity, and PG grade. Based on the binder test results, one best candidate was chosen to apply to the mixture and then the mechanical properties of WMA mixture were evaluated for moisture susceptibility, dynamic modulus, and rutting and fatigue resistance. RESULTS : According to the binder test, WMA asphalt binders showed the similar properties to the original asphalt binder except the penetraion index of WMA additive was a little higher than original binder. From the Superpave mix design, the optimum asphalt content and volumetric properties of WMA mixture were almost the same with those of hot mix asphalt (HMA) mixture even though the production and compaction temperatures were $30^{\circ}C$ lower for the WMA mixture. From the first set of performance evaluation, it was found that the WMA mixture would have some problem in moisture susceptibility. The additive was modified to improve the resistance to moisture and the second set of performance evaluation showed that the WMA mixture with modified chemical additive would have the similar performance to HMA mixture. CONCLUSIONS : Based on the various laboratory tests, it was concluded that the newly developed chemical WMA additve could be successfully used to produce the WMA mixture with the comparable performance to the HMA mixture. These laboratory evaluations should be confirmed by applying this additive to the field and monitoring the long-term performance of the pavement, which are scheduled in the near future.

• Journal of Animal Science and Technology
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• v.59 no.1
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• pp.1.1-1.11
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• 2017

Background: Intrauterine environment plays a pivotal role in the origin of fatal diseases such as the metabolic syndrome. Diabetes is associated with low-grade inflammatory state and dysregulated adipokines production. The aim of this study is to investigate the effect of maternal diabetes on adipocytokines (adiponectin, leptin and TNF-${\alpha}$) production in F1 offspring in rats. Methods: The offspring groups were as follows: F1 offspring of control mothers under control diet (CD) (CF1-CD), F1 offspring of control mothers under high caloric diet (HCD) (CF1-HCD), F1 offspring of diabetic mothers under CD (DF1-CD), and F1 offspring of diabetic mothers under HCD (DF1-HCD). Every 5 weeks post-natal, 10 pups of each subgroup were culled to obtain blood samples for biochemical analysis. Results: The results indicate that DF1-CD and DF1-HCD groups exhibited hyperinsulinemia, dyslipidemia, insulin resistance and impaired glucose homeostasis compared to CF1-CD (p > 0.05). DF1-CD and DF1-HCD groups had high hepatic and muscular depositions of TGs. The significant elevated NEFA level only appeared in offspring of diabetic mothers that was fed HCD. DF1-CD and DF1-HCD groups demonstrated low serum levels of adiponectin, high levels of leptin, and elevated levels of TNF-${\alpha}$ compared to CF1-CD (p > 0.05). These results reveal the disturbed metabolic lipid profile of offspring of diabetic mothers and could guide further characterization of the mechanisms involved. Conclusion: Dysregulated adipocytokines production could be a possible mechanism for the transgenerational transmittance of diabetes, especially following a postnatal diabetogenic environment. Moreover, the exacerbating effects of postnatal HCD on NEFA in rats might be prone to adipcytokine dysregulation. Furthermore, dysregulation of serum adipokines is a prevalent consequence of maternal diabetes and could guide further investigations to predict the development of metabolic disturbances.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.37-47
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• 2004

In this study the load distribution and settlement of soil nailed-drilled shafts subjected to axial loads were evaluated by a load-transfer approach. Special attention was given to the reinforcing effects of soil nails placed from the shafts to surrounding weathered- and soft-rocks based on an analytical study and a numerical analysis. An analytical method that takes into account the number, the positions on the shaft, the grade, and the inclination angle at which the soil nails are placed was developed using a load transfer curve methods. Through the comparative study, it is found that the prediction by present approach simulates well the general trends observed by the in-situ measurements and numerical results SHAFT 4.0. It is also found that the reinforcing effects of soil nails increases in the order of hard-, soft- and weathered-rock since the ultimate shaft resistance far large bored piles in weathered rocks is fully mobilized after small displacements of the shaft, compared to the soft- and hard-rocks and subsequently the side resistance is transferred down to the soil nails.

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.131-137
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• 2009

The rate of recycling of waste concrete, which represents the majority of construction-related waste, is increasing. However, a general recognition of the inferior qualify of recycled aggregates and their lower grade of compressive strength, bending strength, shear strength, frost resistance and ductility make the application of recycled aggregates to structures insufficient. Therefore, this study conducted material and member experiments by adding steel fiber for the purpose of improving the properties of recycled aggregate concrete. To synthesize the experimental results, it was found that specimens with a 30% steel fiber admixture had levels of compressive strength, tensile strength and frost resistance that were equivalent to or higher than the standard specimen, and that concrete that had a 30% replacement of recycled aggregates with steel fiber was suitable for application to actual structures.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.112-118
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• 2013

In this study, constant loading test (CLT) was performed to evaluate the hydrogen embrittlement resistance for multipass FCA weld metals of 600MPa tensile strength grade. The microstructures of weld metal-2 having the smallest carbon equivalent (Ceq=0.37) consisted of grain boundary ferrite and widmanstatten ferrite in the acicular ferrite matrix. The weld metal-1 having the largest Ceq=0.47, showed the microstructures of grain boundary ferrite, widmanstatten ferrite and the large amount of bainite (vol.%=19%) in the acicular ferrite matrix. The weld metal-3 having the Ceq=0.41, which was composed of grain boundary ferrite, widmanstatten ferrite, and the small amount of bainite (vol.%=9%) in the acicular ferrite matrix. Hydrogen desorption spectrometry (TDS) used to analyze the amount of diffusible hydrogen and trapping site for the hydrogen pre-charged specimens electrochemically for 24 hours. With increasing the current density of hydrogen pre-charging, the released amount of diffusible hydrogen was increased. Furthermore, as increasing carbon equivalent of weld metals, the released diffusible hydrogen was increased. The main trapping sites of diffusible hydrogen for the weld metal having a low carbon equivalent (Ceq=0.37) were grain boundaries and those of weld metals having a relatively high carbon equivalent (Ceq: 0.41~0.47) were grain boundaries and dislocation. The fracture time for the hydrogen pre-charged specimens in the constant loading test was decreased as the carbon equivalent increased from 0.37 to 0.47. This result is mainly due to the increment of bainite that is vulnerable to hydrogen embrittlement.

• Journal of the Korean Wood Science and Technology
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• v.51 no.4
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• pp.253-269
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• 2023

Oriented strand board (OSB) distributed in Korea was collected, and its mechanical properties were investigated according to the International Organization for Standardization (ISO), Japanese Industrial Standards, and Korean Design Standard. Ten types of OSBs were collected, including six types for walls and others for floors. The thickness swelling, moisture content, and density of each product satisfied the ISO standards. All products showed lower formaldehyde emission values than those of the SE0 grade. The internal bonding strengths of all products, except products B, H, and I, met the ISO standards. However, products A, B, C, F, and H did not satisfy the thickness swelling standard of the load-bearing OSB for use in dry conditions. Products D and G showed heavy duty load-bearing OSB for use in humid conditions in terms of internal bonding and bending strength after boiling. In the nail head pull-through force and lateral nail resistance tests, all products met the standards. In terms of the structural bending performance (four points), the six types of OSBs for walls satisfied the standard for bending strength and modulus of elasticity. All the products for flooring met the standard for bending strength but, except for product G, the products did not meet the standard for modulus of elasticity. Although the results of this study cannot represent the performance of all imported OSBs, considering the above results, the water resistance performance of seven types of OSB products did not meet the standard, and 10 types of products did not match the labeling grades.

• Steel and Composite Structures
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• v.50 no.3
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• pp.319-336
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• 2024

Ultra-high-performance concrete (UHPC) has attracted increasing attention in prefabricated steel-concrete composite beams as achieving the onsite construction time savings and structural performance improvement. The inferior replacement and removal efficiency of conventional prefabricated steel-UHPC composite beams (PSUCBs) has thwarted its sustainable applications because of the widely used welded-connectors. Single embedded nut bolted shear connectors (SENBs) have recently introduced as an attempt to enhance demountability of PSUCBs. An in-depth exploration of the mechanical behavior of SENBs in UHPC is necessary to evidence feasibilities of corresponding PSUCBs. However, existing research has been limited to SENB arrangement impacts and lacked considerations on SENB geometric configuration counterparts. To this end, this paper performed twenty push-out tests and theoretical analyses on the shear performance and design recommendation of SENBs. Key test parameters comprised the diameter and grade of SENBs, degree and sequence of pretension, concrete casting method and connector type. Test results indicated that both diameters and grades of bolts exerted remarkable impacts on the SENB shear performance with respect to the shear and frictional responses. Also, there was limited influence of the bolt preload degrees on the shear capacity and ductility of SENBs, but non-negligible contributions to their corresponding frictional resistance and initial shear stiffness. Moreover, inverse pretension sequences or monolithic cast slabs presented slight improvements in the ultimate shear and slip capacity. Finally, design-oriented models with higher accuracy were introduced for predictions of the ultimate shear resistance and load-slip relationship of SENBs in PSUCBs.