• Advances in materials Research
• /
• v.12 no.3
• /
• pp.179-192
• /
• 2023

We have studied the structural and optical properties of the non-doped and Co 0.08 at.%, Co 0.02 at.%, and Co 0.11 at.% doped ZnO nanorods (NRs) synthesized using the simple low-temperature chemical bath deposition (CBD) method at 95℃ for 2 hours. The scanning electron microscope (SEM) images confirmed the morphology of the ZnO NRs are affected by Co incorporation. As observed, the Co 0.08 at.% doped ZnO NRs have a larger dimension with an average diameter of 153.4 nm. According to the International Centre for Diffraction Data (ICDD) number #00-036-1451, the x-ray diffraction (XRD) pattern of non-doped and Co-doped ZnO NRs with the preferred orientation of ZnO NRs in the (002) plane possess polycrystalline hexagonal wurtzite structure with the space group P63mc. Optical absorbance indicates the Co 0.08 at.% doped ZnO NRs have stronger and blueshift bandgap energy (3.104 ev). The room temperature photoluminescence (PL) spectra of ZnO NRs exhibited excitonicrelates ultraviolet (UV) and defect-related green band (GB) emissions. By calculating the UV/GB intensity, the Co 0.08 at.% is the proper atomic percentage to have fewer intrinsic defects. We predict that Co-doped ZnO NRs induce a blueshift of near band edge (NBE) emission due to the Burstein-Moss effect. Meanwhile, the redshift of NBE emission is attributed to the modification of the lattice dimensions and exchange energy.

• Clean Technology
• /
• v.16 no.3
• /
• pp.182-190
• /
• 2010

The feasibility of clean technology to minimize the $CO_2$ emission by recycling and reuse the waste materials and energy have been studied for the cement industry. A life cycle assessment (LCA) was performed for an alternative raw material-supply method to use the molted slag as the major raw material in the cement clinker manufacturing. Using this new method, a 60% of $CO_2$ could be reduced that comes out during the decarboxylation from the cement rotary kiln. The energy-efficiency improvement and the alternative energy methods that had been determined in our previous study through the environmental assessment of cement industry were applied to the study for the reduction of $CO_2$ emission. The natural gas, one of the fossil fuels, was also used as the first choice to get the result at the earliest time by the most economic and the most efficient green technology and to switch into the carbon neutral energy consumption pattern.

• Korean Journal of Environmental Agriculture
• /
• v.42 no.1
• /
• pp.1-7
• /
• 2023

Super absorbent polymers (SAPs) are hydrophilic molecules that can absorb large amounts of water. This study was conducted to investigate the enhancement of the physicochemical properties of sand soil blended with three SAPs imbibed with 100, 150, and 200-fold water. Three treatments were applied, namely, 100SAP, 150SAP, and 200SAP. The three SAPs were blended at concentrations of 0% (control), 3%, 5%, 7%, and 10% with sand. The pH, electrical conductivity, and cation exchangeable capacity (CEC) of soil blended with the three SAPs were pH 6.35-6.46, 0.09-0.65 dS/m, and 1.42-1.92 cmol_c/kg, respectively, and their capillary porosity, total porosity, and saturated hydraulic conductivity were 21.0-29.3%, 39.2-48.7%, and 272-470 mm/hr. CEC, capillary porosity, total porosity, and saturated hydraulic conductivity of soil were positively correlated with the ratio of the SAPs (p<0.01). These results indicate that blending sand soil with SAPs increased CEC, capillary porosity, and saturated hydraulic conductivity, thus improving the nutrient-retention capacity, water-retention capacity, and permeability of the soil.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.6
• /
• pp.761-768
• /
• 2022

In the hope of realizing carbon neutrality, Korea has established the goal of expanding the supply of hydrogen electric vehicles through a roadmap to revitalize the hydrogen economy. A prerequisite for successful supply expansion is securing the safety of hydrogen electric vehicles. Certain parts, such as the hydrogen transport pipe and tank, in hydrogen electric vehicles are exposed to high-pressure hydrogen gas over long periods of time, so the hydrogen enters the grain boundary of material, resulting in a degradation of the parts referred to as hydrogen embrittlement. In addition, since the safety of parts utilizing hydrogen varies depending on the type of material used and its environmental characteristics, the necessity for the enactment of a hydrogen embrittlement regulation has emerged and is still being discussed as a Global Technical Regulation (GTR). In this paper, we analyze a hydrogen compatibility material evaluation method discussed in GTR and present a direction for the development of Korean-type hydrogen compatibility material evaluation methods.

• Restorative Dentistry and Endodontics
• /
• v.47 no.1
• /
• pp.12.1-12.11
• /
• 2022

Objectives: This pilot study aimed to establish the interrelationship between collagen and mast cells in periapical granulomas and periapical cysts. Materials and Methods: An observational cross-sectional study was conducted on the paraffin-embedded tissue sections of 68 specimens (34 periapical granulomas and 34 periapical cysts). The specimens were stained with picrosirius to observe collagen fiber birefringence and anti-tryptase antibody to evaluate the mast cell count immunohistochemically. The mean number and birefringence of collagen fibers, as well as the mean number of mast cells (total, granulated, and degranulated), and the mean inflammatory cell density were calculated. The data obtained were analyzed using the Kruskal Wallis test, Mann Whitney U test, and Spearman correlation test (p < 0.05). Results: The mean number of thick collagen fibers was higher in periapical cysts, while that of thin fibers was higher in granulomas (p = 0.00). Cysts emitted orange-yellow to red birefringence, whereas periapical granulomas had predominantly green fibers (p = 0.00). The mean inflammatory cell density was comparable in all groups (p = 0.129). The number of total, degranulated, and granulated mast cells exhibited significant results (p = 0.00) in both groups. Thick cyst fibers showed significant inverse correlations with inflammation and degranulated mast cells (p = 0.041, 0.04 respectively). Conclusions: Mast cells and inflammatory cells influenced the nature of collagen fiber formation and its birefringence. This finding may assist in the prediction of the nature, pathogenesis, and biological behavior of periapical lesions.

• Journal of People, Plants, and Environment
• /
• v.22 no.6
• /
• pp.563-573
• /
• 2019

The North Korean government conducted its first nuclear test in 2006 and more recently the sixth nuclear test on September 3, 2017. In order to identify how North Korea's nuclear tests have affected the environment, a scientific approach is required. Although North Korea's nuclear tests and their environmental destruction are not a severe threat to the environment of the Korean Peninsula at this time, identifying environmental damage and taking countermeasures in advance are essential to minimize their potential threats to the environments. The purpose of this study is to study the environmental impact of North Korea's nuclear tests using Google Earth image analysis. As a method of the study, we compare Google Earth images taken before and after each nuclear test was conducted in North Korea. To overcome limitations of the suggested comparison method, we cross-checked our results with those of previous scientific research. After the 1st-3rd nuclear tests, green spaces were found to be considerably reduced. In particular, when comparing the Google Earth images before and after the second nuclear test, some ground subsidences were observed. Such subsidences can cause tunnels on the mountainsides and cracks in rocks around the mountains, leading to the release of radioactive materials and contaminating groundwater. Besides, after the 4th-6th nuclear tests, decay and deforestation were observed not in the nuclear test sites, but in their surrounding areas. Especially after the 5th and 6th nuclear tests, the topography and the forests of the surrounding areas were severely damaged. In relation to North Korea's nuclear tests and their impact on the natural environment, we need to prepare various policy measures to reduce North Korea's environmental pollution and natural environment destruction. Those policy measures include the establishment of various cooperative governance between the Korean government, the private sector, the academia, NGOs, and international organizations.

• Fashion & Textile Research Journal
• /
• v.25 no.6
• /
• pp.732-738
• /
• 2023

This study delves into the realm of upcycling beauty design by repurposing discarded CDs, magazines, and fabrics. The study outlines a meticulous process for transforming waste into beauty designs. We created three upcycling beauty design works as part of this investigation. The first creation, called Silver Leaf, uses the silver section of CDs to craft leaves and stems. Achromatic colors are used as makeup to achieve cyber-inspired imagery. After carrying out silver-gray eye makeup, the lips were completed by affixing a CD component. The second creation is a firebird crafted by cutting or folding fashion magazines to create essential items. The colorful firebird image was completed using vivid color makeup of shades such as red and yellow. After proceeding with red eye makeup, the lips were completed by cutting and pasting magazine cutouts. The third piece is a spring flower, which involved selectively cutting lace patterns to complete a beauty design extending from head to face. The colors are spring-themed and encompass pink, yellow, and blue. Pink, blue, and green eyeshadows were applied on the lace, attached from head to face, chest, and lips. This study advocates for the prospect of upcycling beauty design using sustainable materials by repurposing waste resources. It also introduces the possibilities of creative activities in this field through upcycling. The study aims to play a role in changing the perception of environmental conservation, a concern of our times, through the use of sustainable resources.

• Advances in nano research
• /
• v.15 no.5
• /
• pp.467-484
• /
• 2023

Despite the significant features of fiber-reinforced cementitious composites (FRCCs), including better mechanical, fractural, and durability performance, their high content of cement has restricted their use in the construction industry. Although ground granulated blast furnace slag (GGBFS) is considered the main supplementary cementitious material, its slow pozzolanic reaction stands against its application. The addition of nano-sized mineral modifiers, including nano-silica (NS), is an alternative to address the drawbacks of using GGBFS. The main object of this empirical and numerical research is to examine the effect of NS on the strain-hardening behavior of cementitious composites; ten mixes were designed, and five levels of NS were considered. This study proposes a new method, using a four-point bending test to assess the use of nano-silica (NS) on the flexural behavior, first cracking strength, fracture energy, and micromechanical parameters including interfacial friction bond strength and maximum bridging stress. Digital image correlation (DIC) was used for monitoring the initiation and propagation of the cracks. In addition, to attain a deep comprehension of fiber/matrix interaction, scanning electron microscope (SEM) analysis was used. It was discovered that using nano-silica (NS) in cementitious materials results in an enhancement in the matrix toughness, which prevents multiple cracking and, therefore, strain-hardening. In addition, adding NS enhanced the interfacial transition zone between matrix and fiber, leading to a higher interfacial friction bond strength, which helps multiple cracking in the composite due to the hydrophobic nature of polypropylene (PP) fibers. The findings of this research provide insight into finding the optimum percent of NS in which both ductility and high tensile strength of the composites would be satisfied. As a concluding remark, a new criterion is proposed, showing that the optimum value of nano-silica is 2%. The findings and proposed method of this study can facilitate the design and utilization of green cementitious composites in structures.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.48 no.1
• /
• pp.42-47
• /
• 2024

The value of silkworms as functional health food materials has increased, as has the interest in its disease control for stable production, and in the economic value of entomopathogenic microorganisms. In this study, we isolated and identified disease-causing fungi from white muscardine silkworms, and confirmed whether this strain could produce white muscardine silkworms. For the analysis of the cause of white muscardine disease in the infected silkworms, the fungi and prokaryotes causing the disease were identified, isolated, and identified using metagenome analysis. Metagenomic analysis detected a large amount of the fungus Metarhizium rileyi in silkworms, and a large amount of the bacterium Enterococcus mundtii, which was presumed to be the causative agent of the disease. For accurate identification of the fungi, these were purified by culture medium, and sequencing and phylogenetic tree analyses were performed using an internal transcribed spacer. As a result, M. rileyi, Cladosporium cladosporioides, and C. tenuissimum were identified. In general, M. rileyi is known to form green conidia, but in this study, white-yellow conidia were formed, indicating that the exact causative agent of the fungal disease cannot be estimated by diagnosing the symptoms. Thus, a diagnostic method is necessary for the continuously collection of required pathogens, and identifying their morphological and genetic characteristics.

• Imaging Science in Dentistry
• /
• v.54 no.1
• /
• pp.43-48
• /
• 2024

Purpose: Oral hygiene, maintained through plaque control, helps prevent periodontal disease and dental caries. This study was conducted to examine the accuracy of plaque detection with an intraoral scanner(IOS) compared to images captured with an optical camera. Materials and Methods: To examine the effect of color tone, artificial tooth resin samples were stained red, blue, and green, after which images were acquired with a digital single-lens reflex (DSLR) camera and an IOS device. Stained surface ratios were then determined and compared. Additionally, the deviation rate of the IOS relative to the DSLR camera was computed for each color. In the clinical study, following plaque staining with red disclosing solution, the staining was captured by the DSLR and IOS devices, and the stained area on each image was measured. Results: The stained surface ratios did not differ significantly between DSLR and IOS images for any color group. Additionally, the deviation rate did not vary significantly across colors. In the clinical test, the stained plaque appeared slightly lighter in color, and the delineation of the stained areas less distinct, on the IOS compared to the DSLR images. However, the stained surface ratio was significantly higher in the IOS than in the DSLR group. Conclusion: When employing IOS with dental plaque staining, the impact of color was minimal, suggesting that the traditional red stain remains suitable for plaque detection. IOS images appeared relatively blurred and enlarged relative to the true state of the teeth, due to inferior sharpness compared to camera images.