• The Journal of Engineering Geology
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• v.31 no.1
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• pp.67-81
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• 2021

Grouting is used for reinforcement and waterproofing of soft ground to increase its bearing capacity, reduce the impacts of rising or lowering groundwater levels, and reduce subsidence due to vibration and general causes. This study investigated the enhancement of grout strength and hardening time by the addition of reinforcing fibers, and the development of non-cement grouting materials from blast furnace slag. An experiment was performed to measure the increase in grout strength resulting from the addition of 0.5% increments of aramid and carbon reinforcing fibers. The results show that the uniaxial compressive strength of grout increases with increasing content of reinforcing fiber. Comparison of three admixtures of finely powdered blast furnace slag and 10%, 20%, and 30% calcium hydroxide stimulating agent showed that the uniaxial compressive strength of the mixture increases with increasing content of alkaline stimulant; however, the strength was lower than for 100% pure cement. The reaction of calcium hydroxide with blast furnace slag powder, which increases the strength of the grout, is more effective if injected as a solution rather than a powder.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.579-588
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• 2021

Reinforced earth retaining walls have been widely used in recent years, as they are superior from the landscape perspective than normal concrete retaining walls. However, as reinforced earth retaining walls are made of various materials depending on site, existing design methods cannot secure stability, and a variety of problems have occurred. Studies on the design and stability analysis methods, which are different from existing methods, have been conducted to address these problems. This study conducted a stability investigation using numerical analysis, and blocks of reinforced earth retaining walls were individually applied, which is different from pre-existing numerical analyses. To verify the input values of the numerical analysis when applying individual blocks, real-scale experiments of the friction characteristics between the blocks and the connection properties between the blocks and stiffener were conducted. The applicability of the block conditions, which were the same as those of real sites, was verified through numerical analysis, and will be used for the stability review and design of various combinations of blocks and stiffeners.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.507-522
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• 2021

Specific survey objectives often cannot be met using only one geophysical method, as each method's results are influenced by the specific physical properties of subsurface materials. In particular, areas susceptible to geological hazards require investigation using more than one method in order to reduce risks to life and property. Instead of analyzing the results from each method separately, this work develops a four-quadrant criterion for classifying areas of levees as safe or weak. The assessment is based on statistically determined thresholds of seismic velocity (P-wave velocity from seismic refraction and S-wave velocity from multichannel analysis of surface waves) and electrical resistivity. Thresholds are determined by subtracting the standard deviation from the mean during performance testing of this correlation technique applied to model data of four horizontal and inclined fracture zones. Compared with results from the crossplot of resistivity and P-wave velocity, crossplot analysis using resistivity and S-wave velocity data provides more reliable information on the soil type, ground stiffness, and lithological characteristics of the levee system. A loose and sandy zone (represented by low S-wave velocity and high resistivity) falling within the second quadrant is interpreted to be a weak zone. This interpretation is well supported by the N values from standard penetrating test for the central core.

• Journal of the Korean Wood Science and Technology
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• v.31 no.5
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• pp.72-79
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• 2003

In reliability based design(RBD) method, the distribution characteristics of mechanical properties of material are basic input variable. Therefore, distribution type and parameters of mechanical properties should be determined accurately. Until now, the properties were derived from tests with small, clear specimens. However, the test conditions should emulate as nearly as possible the way in which the timber would be used in practice and the test results should, as closely as possible, reflect the structural end use conditions to which the timber products would be subjected. In this study, structural timbers (38mm by 140mm, 3.0m long) were graded by visual assessment of growth characteristics and defects. And then bending tests were conducted on 498 structural size timbers. For each grade, the distribution type and the parameters of mechanical properties were determined for each grade. For the determination of best-fit distribution type, comparing of square error between distribution types and KS test were conducted. Best-fit distribution type of bending strength(MOR) is weibull distribution for all grade. In case of MOE, normal distribution is best-fit.

• Journal of Mushroom
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• v.20 no.4
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• pp.263-269
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• 2022

This study investigated the culture characteristics of Cryptoporus volvatus, whichis grow naturally in Korea, to determine the suitable environmental conditions for its cultivation. The physiological characteristics of the mycelia were assessed according to the cultivation conditions, to determine the optimal conditions for artificial cultivation. The visual characteristics of the hyphae of Cryptoporus volvatus KACC52303 included an irregular and uneven surface and a fuzzy or cotton-like texture. Under the microscope, its microstructure showed pre-chlamydospore formation, but no clamps were seen. The appropriate culture temperature was found to be a medium/high temperature of approximately 25-30℃, and the optimal pH was found to have a wide range from weakly acidic (pH 4) to neutral (pH 7). In the optimal nutrient source experiment, hyphal growth was shown to be fair in a mixed medium with 2.5% dextrin as the carbon source and 0.1% yeast extract as the organic nitrogen source. Among the various amino acids, organic acids, and inorganic salts tested, the fastest hyphal growth was observed in the presence of leucine, acetic acid or gluconic acid, and KCl or KH₂PO₄, respectively. The column test showed that the best mycelial growth occurred in a mixed medium of 80% pine sawdust, 10% rice bran, and 10% corncob sawdust.

• Korean Journal of Food Science and Technology
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• v.54 no.4
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• pp.391-397
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• 2022

This study aimed to verify the antidiabetic effects of the unripe black raspberry extract (UBRE) in obese diabetic mice. For the experiment, animal model mice were divided into six groups: normal control, diabetic control, three experimental groups (treated with 75, 150, and 300 mg/kg single dose of UBRE), and a positive control (200 mg/kg metformin). The groups treated with 300 mg/kg UBRE and metformin had significantly reduced blood glucose and triglyceride levels in the diabetic mice compared to those in the vehicle control group. In addition, histopathological evaluation showed that UBRE increased the Langerhans area, cell number, and insulin concentration in the pancreatic islets of db/db mice. Therefore, UBRE exerts significant antidiabetic effects by decreasing the blood glucose and lipid levels, suggesting that it can be consumed as a functional diet for diabetic patients.

• The Journal of Korean Medicine
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• v.43 no.1
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• pp.6-17
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• 2022

Objectives: This study describes the implementation of a training course that aimed to increase the competency of undergraduate students of Korean medicine at a single college to obtain informed consent and perform bee venom acupuncture using an objective structured clinical examination (OSCE). Methods: We developed and implemented a short training course for 111 fourth-year students of Korean medicine during their clinical rotation at the Department of Acupuncture and Moxibustion Medicine. Lectures were conducted on the effects of and hypersensitivity reactions to bee venom acupuncture, obtaining informed consent, performing skin test and bee venom acupuncture. Due to the COVID-19 pandemic, some students were offered online lectures, and some could not experience the performance of OSCE in person. A survey with 16 closed and three open questions was used to investigate self-efficacy, opinions about the online lectures, and the OSCE. Results: Out of 111 questionnaires, 104 were completed (94%). Students were generally satisfied with the online lectures and OSCE. For the subjective questionnaire about what was helpful in the training of bee venom acupuncture techniques and OSCE, the authenticity of the teaching method was recorded the highest. Conclusions: This study showed that online lectures were effective in teaching clinical skills of Korean Medicine. It is necessary to produce standard educational materials for clinical skills of Korean Medicine, and studies to analyze the reliability and validity of OSCE are needed.

• Journal of Practical Engineering Education
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• v.14 no.1
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• pp.119-125
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• 2022

Materials used for education are materials such as SM20C, Al6061, and acrylic. SM20C materials are carbon steel and are often used in certification tests and functional competitions, but are also widely used in industrial sites. The Al6061 material is said to be a material that has lower hardness and stronger flexibility than carbon steel, so it is a material that generates a lot of compositional selection of tools. If students are taught practical training using acrylic materials, vibration occurs due to excessive cutting in some parts and damage to the tool occurs. In this process, we examine to what extent the impact on the 2NC head, which is a five-axis equipment, can affect precision control. The weakest part of the five-axis equipment can be said to be the weakest part of the head that controls the AC axis. When the accuracy and cumulative tolerance of this part occur, the accuracy of all products decreases. Therefore, the core part of the 2NC head, the spindle housing, was carried out using an Al7075 T6 (Alcoa, USA) material. In the process of vibration and cutting applied to this material, the analysis was conducted to find out the value applied to the finite element analysis under extreme conditions. It is hoped that this analysis data will help students see and understand the structure of 5-axis machining rather than 5-axis cutting.

• Geophysics and Geophysical Exploration
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• v.25 no.3
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• pp.129-139
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• 2022

Analog-based streamers for ultra-high-resolution seismic surveys are capable of additional noise ingress in water, but the specifications cannot be expanded through interconnections. Foreign-produced digital streamers have been introduced and used primarily at domestic research institutes; however, the cost is high and smooth maintenance is challenging. This study investigates the localization of ultra-high-resolution digital streamers capable of high-resolution imaging of a geological structure. A digital streamer capable of 24-bit, 10 kHz digital sampling of up to 64 channel data was developed through research and development. Various quantitative specifications of the system were designed and developed close to the benchmark model, Geometrics' GeoEel streamer, and the number of modules that make up the system was drastically reduced, reducing development costs and making it easier to use. The field applicability of the developed streamer system was evaluated in an in situ experiment conducted in the waters around the Port of Yeong-il Bay in Pohang in April 2022.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.5
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• pp.555-566
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• 2023

In this study, a composite phase change material (CPCM) produced using the SOL-GEL technique was developed as a thermal energy storage medium for low-temperature applications. Tetradecane and activated carbon (AC) were used as the core and supporting materials, respectively. The tetradecane phase change material (PCM) was impregnated into the porous structure of AC using the vacuum impregnation method, and a thin layer of silica gel was coated on the prepared composite using the SOL-GEL process, where tetraethyl orthosilicate (TEOS) was used as the silica source. The thermal performance of the CPCM was analysed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC results showed that the pure tetradecane PCM had melting and freezing temperatures of 6.4℃ and 1.3℃ and corresponding enthalpies 226 J/g and 223.8 J/g, respectively. The CPCM exhibited enthalpy of 32.98 J/g and 27.7 J/g during the melting and freezing processes at 7.1℃ and 2.4℃, respectively. TGA test results revealed that the AC is thermally stable up to 500℃, which is much higher than the decomposition temperature of the pure tetradecane, which is around 120℃. Moreover, in the case of AC-PCM and CPCM thermal degradation started at 80℃ and 100℃, respectively. The chemical stability of the CPCM was studied using Fourier-transform infrared (FT-IR) spectroscopy, and the results confirmed that the developed composite is chemically stable. Finally, the surface morphology of the AC and CPCM was analysed using scanning electron microscopy (SEM), which confirmed the presence of a thin layer of silica gel on the AC surface after the SOL-GEL process.