• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.5
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• pp.355-374
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• 2022

Soil conditioning improves the performance of EPB (earth pressure balance) shield TBMs (tunnel boring machines) by reducing shear strength, enhancing workability of the excavated soil, and supporting the tunnel face during EPB tunnelling. The mechanical and rheological behavior of the excavated muck mixed with additives should be properly evaluated to determine the optimal additive injection condition corresponding to each ground type. In this study, the laboratory pressurized vane test apparatus equipped with a vane-shaped rheometer was developed to reproduce the pressurized condition in the TBM chamber and quantitively evaluate rheological properties of the soil specimens. A series of the pressurized vane tests were performed for an artificial sand soil by changing foam injection ratio (FIR) and polymer injection ratio (PIR), which are the injection parameters of the foam and the polymer, respectively. In addition, the workability of the conditioned soil was evaluated through the slump test. The peak and yield stresses of the conditioned soil with respect to the injection parameters were evaluated through the rheogram, which was derived from the measured torque data in the pressurized vane test. As FIR increased or PIR decreased, the workability of the conditioned soil increased, and the maximum torque, peak stress, and yield stress decreased. The peak stress and yield stress of the specimen from the laboratory pressurized vane test correspond to the workability evaluated by the slump tests, which implies the applicability of the proposed test for evaluating the rheological properties of excavated soil.

• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.507-517
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• 2022

The PhotoAcoustic Microscopy (PAM) has been proved to be a useful tool for biological and medical applications due to its high spatial and contrast resolution. PAM is based on transmission of laser pulses and reception of PA signals. Since the strength of PA signals is generally low, not only are high-performance optical and acoustic modules required, but high-performance electronics for imaging are also particularly needed for high-quality PAM imaging. Most PAM systems are implemented with a combination of several pieces of equipment commercially available to receive, amplify, enhance, and digitize PA signals. To this end, PAM systems are inevitably bulky and not optimal because general purpose equipment is used. This paper reports a PA signal receiving system recently developed to attain the capability of improved Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR) of PAM images; the main module of this system is a low noise, wideband signal receiver that consists of two low-noise amplifiers, two variable gain amplifiers, analog filters, an Analog to Digital Converter (ADC), and control logic. From phantom imaging experiments, it was found that the developed system can improve SNR by 6.7 dB and CNR by 3 dB, compared to a combination of several pieces of commercially available equipment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.289-298
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• 2023

In this study, the development of a self-healing concrete waterproofing agent was examined, focusing on its manufacturing and waterproofing properties. The optimal ratio using microcapsules for the concrete waterproofing agent was determined through assessments of flow, compressive strength, and permeability conducted during the mortar stage. These findings aimed to provide fundamental data for evaluating the self-healing properties of the concrete waterproofing agent designed for use in concrete structures. The self-healing concrete waterproofing agent was comprised of three types of inorganic materials commonly used for repair purposes. From experimental results, a composition ratio with a high potassium silicate content, referred to as SIM-2, was found suitable. A surfactant mixing ratio of 0.03 % was identified to enhance the dispersibility of the concrete waterproofing agent, while a mixing ratio of 0.2 % distilled water was deemed suitable for viscosity adjustment. For the magnetic self-healing concrete waterproofing agent's healing agent, using microcapsules in the range of 0.5 % to 0.7 % met the KS F 4949 and KS F 4926 standards.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.2
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• pp.206-210
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• 2017

Objective: A study was conducted to test six threonine (Thr) levels (0.39%, 0.44%, 0.49%, 0.54%, 0.59%, and 0.64%) to estimate the optimal dietary Thr requirements for Longyan laying ducks from 17 to 45 wk of age. Methods: Nine hundred Longyan ducks aged 17 wk were assigned randomly to the six dietary treatments, where each treatment comprised six replicate pens with 25 ducks per pen. Results: Increasing the Thr level enhanced egg production, egg weight, egg mass, and the feed conversion ratio (FCR) (linearly or quadratically; p<0.05). The Haugh unit score, yolk color, albumen height, and the weight, percentage, thickness, and breaking strength of the eggshell did not response to increases in the Thr levels, but the albumen weight and its proportion increased significantly (p<0.05), whereas the yolk weight and its proportion decreased significantly as the Thr levels increased. Conclusion: According to a regression model, the optimal Thr requirement for egg production, egg mass, and FCR in Longyan ducks is 0.57%, while 0.58% is the optimal level for egg weight from 17 to 45 wk of age.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.1
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• pp.25-39
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• 2022

This study was conducted to evaluate the manufacturing process of non-sintered cement for the safe containment of radioactive waste using low level or ultra-low level radioactive waste soil generated from nuclear-decommissioning facilities, clay minerals, and blast furnace slag (BFS) as an industrial by-product recycling and to characterize the products using mineralogical and morphological analyses. A stepwise approach was used: (1) measuring properties of source materials (reactants), such as waste soil, clay minerals, and BFS, (2) manufacturing the non-sintered cement for the containment of radioactive waste using source materials and deducing the optimal mixing ratio of solidifying and adjusting agents, and (3) conducting mineralogical and morphological analyses of products from the hydration reactions of manufactured non-sintered cement solidifier (NSCS) containing waste concrete generated from nuclear-decommissioning facilities. The analytical results of NSCS using waste soil and clay minerals confirmed none of the hydration products, but calcium silicate (CSH) and ettringite were examined as hydration products in the case of using BFS. The compressive strength of NSCS manufactured with the optimum mixing ratio and using waste soil and clay minerals was 3 MPa after the 28-day curing period, and it was not satisfied with the acceptance criteria (3.44 MPa) for being brought in disposal sites. However, the compressive strength of NSCS using BFS was estimated to be satisfied with the acceptance criteria, despite manufacturing conditions, and it was maximized to 27 MPa at the optimal mixing ratio. The results indicate that the most relevant NSCS for the safe containment of radioactive waste can be manufactured using BFS as solidifying agent and using waste soil and clay minerals as adsorbents for radioactive nuclides.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.6
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• pp.1129-1136
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• 2001

This study was to investigate the suitability of six domestic wheat cultivars for the Korean-style steamed bread made under optimal conditions. Six wheat flours milled from cultivars of Greu, Kumgang, Eunpa, Taptong Kobun, and Allgreu contained 13.8, 13.7, 13.7, 13.0, 11.7, 11.0% of protein. Control bread was made from blend (protein 10.5%) of 50% high strength and 50% low strength wheat flours milled from imported wheats. The volume of steamed bread made from Kumgang was highest followed by Eunpa, Tapdong, Kobun, Greu, control bread, Allgreu. Especially, the bread qualities of Kumgand and Kobun were superior to the control bread, showing better surface characteristics such as smoothness, glossiness, and whiteness, better shapes and desirable texture. Domestic wheat flours, having medium strength with high protein content above 13.0% were suitable for steamed bread except for Greu. Volumes of steamed bread made from domestic wheat flours were correlated with protein and ash content, flour color (L value), farinograph dough development time and stability, whereas spread ratio, total bread score and overall acceptability were correlated with farinograph dough stability It is concluded that flour quality is more important factor than protein content when domestic wheat flours are chosen for Korean-style steamed bread

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.555-562
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• 2016

Seismic design of braced frames that simultaneously considers economic issues and structural performance represents a rather complicated engineering problem, and therefore, a systematic and well-established methodology is needed. This study proposes a multi-objective seismic design method for an inverted V-braced frame with suspended zipper struts that uses the non-dominated sorting genetic algorithm-II(NSGA-II). The structural weight and the maximum inter-story drift ratio as the objective functions are simultaneously minimized to optimize the cost and seismic performance of the structure. To investigate which of strength- and performance-based design criteria for braced frames is the critical design condition, the constraint conditions on the two design methods are simultaneously considered (i.e. the constraint conditions based on the strength and plastic deformation of members). The linear static analysis method and the nonlinear static analysis method are adopted to check the strength- and plastic deformation-based design constraints, respectively. The proposed optimal method are applied to three- and six-story steel frame examples, and the solutions improved for the considered objective functions were found.

• Journal of Mushroom
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• v.21 no.3
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• pp.185-189
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• 2023

This study was conducted to develop a renewable and sustainable bio-material to replace polystyrene (EPS) in fungal-mycelium-based composite using agricultural by-products. Four mushrooms (Ganoderma lucidum, Fomitella fraxinea, Phellinus linteus, and Schizophyllum commune) were cultured in an oak sawdust plus rice bran substrate to select the mushroom with the best growth. The mycelia of G. lucidum showed the best growth. To investigate the optimal mixing ratio with spent mushroom substrate (SM) and oak sawdust (OS), samples were prepared by mixing SM and OS at ratios of 50%:50%, 60%:40%, and 80%:20% (w/w). Each substrate was then inoculated with G. lucidum. G. lucidum showed the best mycelial growth of 140.0 mm in the substrate with SM and OS mixed at a 60%:40% ratio. It was also found that the substrate with SM and OS mixed at a 60%:40% ratio had the best handling properties. The compressive strength of mycelial materials inoculated with G. lucidum was in the range of 300-302 kgf mm^-1, and the materials were four times stronger than polystyrene materials. These results indicate that substrates comprising spent mushroom substrate mixed with oak sawdust can be successfully upcycled to mycelium-based composite materials using G. lucidum. This represents a sustainable approach.

• Polymer(Korea)
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• v.39 no.1
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• pp.40-45
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• 2015

Simple poor-cosolvent casting was used to surface treat biodegradable elastic poly(L-lactide-co-${\varepsilon}$-caprolactone) (PLCL; 50:50) copolymer films that presented lotus-leaf-like structures. We evaluated whether the lotus-leaflike-structured PLCL (L-PLCL) films could be used as a biomaterial for artificial vascular grafts. The surface morphology, hydrophobicity, and antithrombotic efficiency of the films were examined while immersed in platelet-rich plasma (PRP) using scanning electron microscopy (SEM) and a contact angle meter. The recovery and crystallinity of the films were measured using a tensile-strength testing machine and an X-ray diffractometer, respectively. The solvent containing acetic acid, as a poor co-solvent, and methylene chloride mixed in a 1:2 ratio produced an optimal PLCL film with a water contact angle of approximately $124^{\circ}$. Furthermore, the surface of the L-PLCL films immersed in PRP showed a lower rate of platelet adhesion (<10%) than that of the surface of an untreated PLCL film immersed in PRP.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.1
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• pp.86-91
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• 1995

This experiment was conducted to understand the response on sowing rates at furrow sowing of rice in paddy field. As sowing rates was increased, the number of seedling stand per$m^2$ was icreased, while panicie number per plant was decreased slightly. Leaf area at heading stage and effective tiller ratio were decreased with increasing of sowing rates, but heading date was not defferent among sowing rates. According to sowing rates was increased, culm length, panicle length, breaking strength, culm diameter were decreased, while lodging index was increased. Also, field lodging was observed in the higer sowing rates over 5kg/l0a. Althougth the panicle number per $m^2$ was increased with increasing of sowing rates, spike let per panicle and percent of filled spikelet were decreased. According to the result from the path coefficient analysis, percent of filled spikelets well identified to be the most influential variables on the variability in rice yield, so that improving percent of filled spikelets by inhibition of field lodging was the important matter to increase the yield. The optimal sowing rate and the number of seedling stand were estimated to be 4.5kg/l0a and 105 per $m^2$ respectively.