• Journal of Nutrition and Health
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• v.56 no.5
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• pp.469-482
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• 2023

Purpose: Obesity has emerged as a critical global public health concern as it is associated with and increases susceptibility to various diseases. This condition is characterized by the excessive enlargement of adipose tissue, primarily stemming from an inequity between energy intake and expenditure. The purpose of this study was to investigate the potential of sweet pumpkin powder in mitigating obesity and metabolic disorders in leptin-deficient obese (ob/ob) mice and to compare the effects of raw sweet pumpkin powder (HNSP01) and heat-treated sweet pumpkin powder (HNSP02). Methods: Leptin-deficient obese mice were fed a diet containing 10% HNSP01 and another containing 10% HNSP02 for 6 weeks. Results: The supplementation of ob/ob mice with HNSP01 and HNSP02 resulted in decreased body weight gain, reduced adipose tissue weight, and a smaller size of lipid droplets in the adipose tissue and liver. Furthermore, the ob/ob-HNSP01 and ob/ob-HNSP02 supplemented groups exhibited lower levels of triglycerides, total cholesterol, low-density lipoprotein cholesterol, fasting blood glucose, and insulin, as well as a reduced atherogenic index in comparison with the control group. Molecular analysis also demonstrated that the intake of HNSP01 and HNSP02 resulted in a diminished activation of factors associated with fatty acid synthesis, including acetyl-CoA carboxylase and fatty acid synthase, while concurrently enhancing factors associated with lipolysis, including adipose triglyceride lipase and hormone-sensitive lipase, in the adipose tissue. Conclusion: Taken together, these findings collectively demonstrate the potential of sweet pumpkin powder as a functional food ingredient with therapeutic properties against obesity and its associated metabolic disorders, such as insulin resistance and dyslipidemia.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.1-10
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• 2023

Due to the development of the industrial revolution, regulations on exhaust emissions have been continuously strengthened to reduce the rapidly increasing greenhouse gas emissions. The use of environmentally friendly fuels is essential to meet these regulations. Hydrogen has been attracting attention as a future environmentally friendly fuel, but due to its material properties, it faces significant challenges in handling and storage. As an alternative, ammonia has been proposed. Ammonia can be easily liquefied at room temperature compared to hydrogen and has a high energy density. In order to examine the applicability of ammonia as an engine fuel, experiments were conducted to investigate the effects of changes in combustion control parameters in a direct injection ammonia combustion engine. The experiments were conducted by varying two variables: spark timing and excessive air ratio. Observations were made on combustion stability and the trends of exhaust emissions such as nitrogen oxides and unburned ammonia under the conditions of an engine speed of 1,500 rpm and medium to high loads (brake torque of 200 Nm). By optimizing the combustion control parameters, conditions for stable combustion even when using ammonia as the sole fuel were identified, and plans are underway to apply strategies for future expansion of the operating range.

• Clean Technology
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• v.30 no.2
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• pp.105-112
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• 2024

Globally, the demand for electric vehicles has surged due to greenhouse gas regulations related to climate change, leading to an increase in the production of used batteries as a consequence of the battery life issue. This study aims to selectively leach and recover valuable metal lithium from the cathode material of spent LFP (LiFePO₄) batteries among lithium-ion batteries. Generally, the use of inorganic acids results in the emission of toxic gases or the generation of large quantities of wastewater, causing environmental issues. To address this, research is being conducted to leach lithium using organic acids and other leaching agents. In this study, selective leaching was performed using the organic acid methane sulfonic acid (MSA, CH₃SO₃H). Experiments were conducted to determine the optimal conditions for selectively leaching lithium by varying the MSA concentration, pulp density, and hydrogen peroxide dosage. The results of this study showed that lithium was leached at approximately 100%, while iron and phosphorus components were leached at about 1%, verifying the leaching efficiency and the leaching rates of the main components under different variables.

• Korean Journal of Materials Research
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• v.34 no.4
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• pp.185-193
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• 2024

In this study, NASICON-type Li_1+XGa_XTi_2-X(PO₄)₃ (x = 0.1, 0.3 and 0.4) solid-state electrolytes for all-solid-state batteries were synthesized through the sol-gel method. In addition, the influence on the ion conductivity of solid-state electrolytes when partially substituted for Ti⁴⁺ (0.61Å) site to Ga³⁺ (0.62Å) of trivalent cations was investigated. The obtained precursor was heat treated at 450 ℃, and a single crystalline phase of Li_1+XGa_XTi_2-X(PO₄)₃ systems was obtained at a calcination temperature above 650 ℃. Additionally, the calcinated powders were pelletized and sintered at temperatures from 800 ℃ to 1,000 ℃ at 100 ℃ intervals. The synthesized powder and sintered bodies of Li_1+XGa_XTi_2-X(PO₄)₃ were characterized using TG-DTA, XRD, XPS and FE-SEM. The ionic conduction properties as solid-state electrolytes were investigated by AC impedance. As a result, Li_1+XGa_XTi_2-X(PO₄)₃ was successfully produced in all cases. However, a GaPO₄ impurity was formed due to the high sintering temperatures and high Ga content. The crystallinity of Li_1+XGa_XTi_2-X(PO₄)₃ increased with the sintering temperature as evidenced by FE-SEM observations, which demonstrated that the edges of the larger cube-shaped grains become sharper with increases in the sintering temperature. In samples with high sintering temperatures at 1,000 ℃ and high Ga content above 0.3, coarsening of grains occurred. This resulted in the formation of many grain boundaries, leading to low sinterability. These two factors, the impurity and grain boundary, have an enormous impact on the properties of Li_1+XGa_XTi_2-X(PO₄)₃. The Li_1.3Ga_0.3Ti_1.7(PO₄)₃ pellet sintered at 900 ℃ was denser than those sintered at other conditions, showing the highest total ion conductivity of 7.66 × 10^-5 S/cm at room temperature. The total activation energy of Li-ion transport for the Li_1.3Ga_0.3Ti_1.7(PO₄)₃ solid-state electrolyte was estimated to be as low as 0.36 eV. Although the Li_1+XGa_XTi_2-X(PO₄)₃ sintered at 1,000 ℃ had a relatively high apparent density, it had less total ionic conductivity due to an increase in the grain-boundary resistance with coarse grains.

• The Journal of the Acoustical Society of Korea
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• v.28 no.6
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• pp.542-547
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• 2009

In this in vivo study, correlations of lumbar and femoral bone mineral densities (BMDs) with calcaneal speed of sound (SOS) were investigated in 36 osteoporotic women. Areal BMDs of the L2-L4 lumbar spine and the right femoral neck were measured by using dual energy X-ray absorptiometry (DEXA). SOS of the right calcaneus was measured by using ultrasound bone densitometry. Pearson's correlation coefficient (r) and level of significance (p) were used to evaluate the correlations between measurements. Lumbar BMD was highly correlated with femoral BMD (r=0.81). Lumbar and femoral BMDs exhibited similar comparable negative correlations with age (r=-0.52 and r=-0.55). A moderate negative correlation was found between calcaneal SOS and age (r=-0.45). Calcaneal SOS was significantly correlated with lumbar and femoral BMDs, with a higher correlation with femoral BMD rather than with lumbar BMD (r=0.54 and r=0.62). However, calcaneal SOS may not be an optimum index for the estimation of BMD of the most important fracture sites, such as the lumbar and the femur, because it showed lower correlations with lumbar and femoral BMDs compared to that with calcaneal BMD. Therefore, the development of a quantitative ultrasound technology for the direct measurement of acoustic properties at the lumbar and the femur is required to estimate BMD of these sites more accurately.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.3
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• pp.18-32
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• 2024

This study aims to analyze the summer human thermal environment in Jeju City's outdoor parking lots by measuring microclimate data and comparing pavement and vegetation albedoes and elements through computer simulations. In measured cases, results due to albedo showed no significance, but there was a significant difference between sunny and shaded areas by trees. The sunny area had a PET (physiological equivalent temperature) in the 'very hot' level, while the shaded area exhibited a 2-step lower 'warm' level. UTCI (universal thermal climate index) also showed that the sunny area was in the 'very strong heat stress' level, whereas the shaded area was 1-step lower in the 'strong heat stress' level, confirming the role of trees in reducing incoming solar radiant energy. Simulation results, using the measured albedoes, closely resembled the measured results. Regarding vegetation, scenarios with a wide canopy, high leaf density, and narrow planting spacing were effective in mitigating the human thermal environment, and the differences due to tree height varied across scenarios. The scenario with the lowest PET value was H9W9L3D8 (tree height 9m, canopy width 9m, leaf area index 3.0, planting spacing 8m), indicating a 0.7-step decrease compared to the current landscaping scenario. Thus, it was confirmed that, among landscaping elements, trees have a significant impact on the summer human thermal environment compared to ground pavement.

• Journal of the Korean Regional Science Association
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• v.40 no.2
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• pp.107-130
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• 2024

Urban land surface temperature (LST) change is a major environmental factor that affects the thermal comfort, energy consumption, and health of urban residents. Most studies that explored the relationship between LST and urban built-environment form analyzed only midday LST. This study explores the diurnal variation of summertime LST in Seoul using ECOSTRESS data, which observes LST at various times of the day and analyzes whether the LST variation differs by built environment type. Launched in 2018, ECOSTRESS operates in a non-sun-synchronous orbit, observing LST with a high resolution of 70 meters. This study collected data from early morning (6:25) to evening (17:26) from 2019 to 2022 to build time-series LST. Based on greenery, water bodies, and building form data, eight types of Seoul's built environment were derived by hierarchical clustering, and the LST fluctuation characteristics of each cluster were compared. The results showed that the spatial disparity in LST increased after dawn, peaked at noon, and decreased again, highlighting areas with rapid versus stable LST changes. Low-rise and high-rise compact districts experienced fast, high temperature increases and high variability, while low-density apartments experienced moderate LST increases and low variability. These results suggest urban forms that can mitigate rapid daytime heating.

• Journal of the Korean Electrochemical Society
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• v.27 no.3
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• pp.88-96
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• 2024

Lithium metal has garnered attention as a promising anode active material thanks to its high specific capacity, energy density, and the lowest reduction potential. However, the formation of dendrites, dendritic crystals that arise during the charge and discharge process, has posed safety and lifetime stability challenges. To resolve this, our study has introduced a novel separator design. This separator features a composite coating of vapor-grown carbon fiber, a conductive material in nanofibers, and silver. We have meticulously studied the impact of this innovative separator on the electrochemical properties of the lithium metal anode, unveiling promising results. To confirm the synergistic effect of VGCF and Ag, a separator with no surface treatment and a separator with only VGCF coated on one side were prepared and compared with the Ag-VGCF-separator. In the case of the bare separator, the Li metal surface is covered with dendrites during the initial charge and discharge process. In contrast, both the VGCF-separator and the Ag-VGCF-separator show Li precipitation inside the conductive coating layer coated on the separator surface. Additionally, the Ag-VGCF-separator showed a more uniform precipitate shape than the VGCF-separator. As a result, the Ag-VGCF-separators show improved electrochemical properties compared to the bare separators and the VGCF-separators.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.11
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• pp.1604-1611
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• 2011

In this study we assessed the effects of gamma irradiation (50 kGy) on cookies to which was added various concentrations (1%, 3%, 5%, 7%) of hot water extract from seamustad (Undaria pinnatifida) sporophylls (WEUS) for future industry use. The pH of the dough went down significantly with the addition of WEUS. However, density was not related to that. The spread ratio of the cookies increased significantly as more WEUS was added to the cookie recipe, and cookies containing gamma-irradiated extract were taller than non-irradiated cookies with the same concentration. The loss rate of cookies was the same between control and experiment groups. On the other hand, the leavening rate significantly increased upon the addition of WEUS, and gamma-irradiated cookies were higher than non-irradiated cookies in the same concentration. The L value of cookies was much reduced with higher WEUS content, but the b value showed no significant differences between the control and experiment groups. The a value showed no significant difference for non-irradiated groups, but did for gamma-irradiated groups. Upon the addition of WEUS, hardness was shown to be higher than the control. The antioxidant activity, DPPH radical scavenging, was significantly higher with the control cookies, and upon the addition of WEUS, the gamma-irradiated cookies had higher antioxidant effects than non-irradiated cookies. The sensory evaluation showed that cookies made with WEUS have a positive impact in color, smell, taste, texture, and overall acceptability, but the sensory evaluation worsened with a lot of WEUS. The results of acceptability were higher in cookies with 3% the non-irradiated group and 1% the gamma-irradiated group. These results suggest that the 1% gamma-irradiated group was in the best condition to use in the industry since just a little of it makes exceptional quality, sensory properties, and functionality.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.54 no.2
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• pp.135-142
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• 2009

This experiment was conducted to determine the usability of biodegradable plastic in the mulching cultivation of sweetpotato. For this, we investigated the physical characteristics, biodegradability, leaching, yield, workability, etc. of biodegradable films. Compared with general mulching materials, biodegradable Poly butyleneadipate-co-butylene succinate (PBSA) and PLC+starch showed $2{\sim}27$% higher tensile strength, but $2{\sim}22$% lower elongation and $2{\sim}6$% lower tear strength. In the leaching test on the biodegradable films, heavy metals were detected very little or not at all. As to difference in ground temperature according to mulching material, the temperature was high in order of PLC+starch > PBSA > Low Density Polyethylene (LDPE) > Control during the period from late June to mid July, but in order of LDPE > PLC+starch > PBSA > None during the period from late July to late September. In the mulching cultivation of sweet potato, biodegradable films PBSA (EA, EB, EC) and PLC+starch (DD, DE, DF) began to degrade after 60 days from the cut planting of sweet potato, and over 95% degraded after 120 days. The quantity of roots was 3,070 kg/10a for PBSA, 3,093 kg/10a for PLC-starch, and 2,946 kg/l10a for LDPE, showing no significant difference according to mulching material. Considering the physical characteristics, biodegradability, environment, convenience in harvesting work, yield, etc. of the films in the mulching cultivation of sweet potato, biodegradable films are expected to be very useful.