• Advances in nano research
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• v.16 no.6
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• pp.565-577
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• 2024

Vibration investigation of fluid-filled functionally graded cylindrical shells with ring supports is studied here. Shell motion equations are framed first order shell theory due to Sander. These equations are partial differential equations which are usually solved by approximate technique. Robust and efficient techniques are favored to get precise results. Employment of the Rayleigh-Ritz procedure gives birth to the shell frequency equation. Use of acoustic wave equation is done to incorporate the sound pressure produced in a fluid. Hankel's functions of second kind designate the fluid influence. Mathematically the integral form of the Langrange energy functional is converted into a set of three partial differential equations. A cylindrical shell is immersed in a fluid which is a non-viscous one. These shells are stiffened by rings in the tangential direction. For isotropic materials, the physical properties are same everywhere where the laminated and functionally graded materials, they vary from point to point. Here the shell material has been taken as functionally graded material. After these, ring supports are located at various positions along the axial direction round the shell circumferential direction. The influence of the ring supports is investigated at various positions. Effect of ring supports with empty and fluid-filled shell is presented using the Rayleigh - Ritz method with simply supported condition. The frequency behavior is investigated with empty and fluid-filled cylindrical shell with ring supports versus circumferential wave number and axial wave number. Also the variations have been plotted against the locations of ring supports for length-to-radius and height-to-radius ratio. Moreover, frequency pattern is found for the various position of ring supports for empty and fluid-filled cylindrical shell. The frequency first increases and gain maximum value in the midway of the shell length and then lowers down. It is found that due to inducting the fluid term frequency result down than that of empty cylinder. It is also exhibited that the effect of frequencies is investigated by varying the surfaces with stainless steel and nickel as a constituent material. To generate the fundamental natural frequencies and for better accuracy and effectiveness, the computer software MATLAB is used.

• Composites Research
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• v.37 no.4
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• pp.337-342
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• 2024

Thermosetting composite materials are applied in mobility and structural applications due to their high mechanical strength and thermal properties. Nevertheless, these materials are difficult to recycle or reprocess. Therefore, research is currently underway to introduce vitrimer as a solution to this challenge. In this study, to enable reprocessing and self-healing of structural epoxy, an epoxy containing disulfide bonds was synthesized and added. The addition of disulfide epoxy resulted in a decrease in tensile strength and Young's modulus, but an increase in tensile strain. Analysis of the fracture surface after tensile testing revealed that the addition of disulfide epoxy imparted characteristics of ductile materials. This is attributed to the structure of disulfide epoxy, which primarily involves alkyl chains and bond exchange occurring at the disulfide bonds. It was confirmed that the addition of disulfide epoxy enables self-healing through reprocessing. While reprocessing was not possible with disulfide epoxy content below 17 wt%, it was feasible up to four times with content above 0.25 wt%. This study is expected to contribute to extending the lifespan of structural composites and enhancing recycling possibilities through reprocessing.

• Korean Journal of Agricultural Science
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• v.10 no.2
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• pp.206-211
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• 1983

This study was carried out to compare the feed utilization between pelleted and all-mash diet of similar composition by growing chickens. Day-old broilers (Hubbard) and egg-type chickens(Hy-line) of commercial strain were employed in this experiment. The results obtained were summarized as follows. 1. The chickens fed pelleted diets were heavier than those of birds fed all-mash diets. The Hubbard broilers and Hy-line chickens fed pelleted diets weighed 2,702g and 812g respectively, at 9 weeks of age. In comparison, the Hubbard broilers and Hy-line chickens fed all-mash diets weighed 2,571g and 777g respectively, at 9 weeks of age. 2. The pellet-fed chickens consumed more feeds than birds fed all-mash diets in both types of strain. Feed efficiencies (gain/feed) of Hubbard and Hy-line chickens were 0.38 and 0.26 in pellet feeding groups, and 0.36 and 0.25 in all-mash feeding groups, respectively. The Hy-line chickens fed pelleted diets drank more water than birds fed all-mash diets. 3. Pellet feeding groups produced more dry matter excreta as compared with all-mash feeding groups, reflecting the pattern of feed consumption by these chickens. Nitrogen retention ratio of the Hubbard and Hy-line chickens were 57-67% and 65-73%, respectively. Chickens fed pelleted diets showed 1-4% higher nitrogen retention than chickens fed all-mash diets. 4. The ME/GE ratio of the Hubbard and the Hy-line at 8 weeks of age were 73.4-74.3% and 82.8-83.8%, respectively. Pellet feeding groups showed 1% higher ME/GE ratio than all-mash feeding groups. 5. The dietary productive energy calculated from respiratory quotient was $94.1-102.6kca/kg^{\frac{3}{4}}$ BW/day in pellet feeding groups. The ratios of PE/GE were 41.3-48.9% in pellet feeding groups and 39.0-45.8% in all-mash feeding groups. 6. It appears that pelleting the all-mash diet increases feed consumption and body weight gain of growing chickens. Feed efficiency and energy utilization were also improved by pelleting process. More research work should be done to establish the relationship clearly between feed pelleting and heat increments.

• Korean Journal of Agricultural Science
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• v.9 no.2
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• pp.540-545
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• 1982

An energy metabolism study was conducted with two commercial strains of meat-type chickens, Hubbard and Cobb, and two egg strains, Hy Line and Korean-bred Hanhyup 325. The heat production of growing chickens from each strain were measured by the use of an open-circuit gravimetric respiration calorimeter. The data obtained from this study were summarized as fallows. 1. The average body weight of 9-wk-old Hubbard broilers reared in battery cages was 2,570g/bird. The average body weights of 9-wk-old Hy Line chicks and Hanhyup 325 were 777 and 748g/bird, respectively. 2. At 3 weeks of age, the Hubbard broiler chicks consumed two times the feed consumed by Hy Line chicks (54.6g VS. 26.7g/bird/day). These values increased to 151g and 57.2g/bird/day, respectively, at 8 weeks of age, indicating that the difference in feed intake between meat and egg-type chicks tends to increase as they grow older. In terms of water consumption, the 5-wk-old Hubbard broiler chicks drank $226m{\ell}/bird/day$ as compared with $58m{\ell}$ by Hy Line chicks. These values increased to 282 and $70m{\ell}$, respectively, at 8 weeks of age. 3. The excreta outputs of Hubbard broilers and Hy Line chicks were 18.7 and 6.1g DM/bird/day at 4 weeks of age, and 41.5 and 10.0g DM/bird/day at 8 weeks of age, respectively. 4. The energy metabolizability of broiler chicks were 75.4~77.1% compared to 75.0~83.5% by egg-type chicks. 5. The respiratory quotient (RQ) was between 0.78 and 0.97. There seems to be no difference in RQ between meat and egg-type chicks. The RQ tended to decrease when feed intake was low and vice versa. 6. Both meat and egg-type chicks produced $83.1{\sim}123.1Kcal/kg^{\frac{3}{4}}B.W./day$. The considerably low value of $83Kcal/kg^{\frac{3}{4}}B.W./day$ was obtained when the chicks were off the feed under the stressful conditions. The high value of 123.1Kcal was obtained when the chicken chamber temperature rose to $27{\sim}34^{\circ}C$.

• Korean Journal of Environmental Biology
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• v.34 no.4
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• pp.304-313
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• 2016

One of the issues currently facing nuclear power plants is how to store spent nuclear waste materials which are contaminated with radionuclides such as $^{134}Cs$, $^{135}Cs$, and $^{137}Cs$. Bioremediation processes may offer a potent method of cleaning up radioactive cesium. However, there have only been limited reports on $Cs^+$ tolerant bacteria. In this study, we report the isolation and identification of $Cs^+$ tolerant bacteria in environmental soil and sediment. The resistant $Cs^+$ isolates were screened from enrichment cultures in R2A medium supplemented with 100 mM CsCl for 72 h, followed by microbial community analysis based on sequencing analysis from 16S rRNA gene clone libraries(NCBI's BlastN). The dominant Bacillus anthracis Roh-1 and B. cereus Roh-2 were successfully isolated from the cesium enrichment culture. Importantly, B. cereus Roh-2 is resistant to 30% more $Cs^+$ than is B. anthracis Roh-1 when treated with 50 mM CsCl. Growth experiments clearly demonstrated that the isolate had a higher tolerance to $Cs^+$. In addition, we investigated the adsorption of $0.2mg\;L^{-1}$ $Cs^+$ using B. anthracis Roh-1. The maximum $Cs^+$ biosorption capacity of B. anthracis Roh-1 was $2.01mg\;g^{-1}$ at pH 10. Thus, we show that $Cs^+$ tolerant bacterial isolates could be used for bioremediation of contaminated environments.

• Tunnel and Underground Space
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• v.30 no.3
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• pp.256-269
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• 2020

The objective of this study is to evaluate the stress thresholds in crack development and the corrected fracture toughness of KURT granite under dry and saturated conditions. The stress thresholds were identified by calculation of inelastic volumetric strain from an uniaxial compression test. The corrected fracture toughness was estimated by using the Level II method (Chevron Bend specimen), suggested by ISRM (1988), in which non-linear behaviors of rock was taken into account. Average crack initiation stress(σ_ci) and crack damage stress(σ_cd) under a dry condition were 91.1 MPa and 128.7 MPa. While, average crack initiation stress(σ_ci) and crack damage stress(σ_cd) under a saturated condition were 58.2 MPa and 68.2 MPa. The crack initiation stress and crack damage stress of saturated ones decreased 36% and 47% respectively compared to those of dry specimens. A decrease in crack damage stress is relatively larger than that of crack initiation stress under a saturated condition. This indicates that the unstable crack growth can be more easily generated because of the saturation effect of water compared to the dry condition. The average corrected fracture toughness of KURT granite was 0.811 MPa·m^0.5. While, the fracture toughness of saturated KURT granite(K_CB) was 0.620 MPa·m^0.5. The corrected fracture toughness of rock in saturated condition decreases by 23.5% compared to that in dry condition. It is found that the resistance to crack propagation decreases under the saturated geological condition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.306-318
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• 2018

In order to evaluate the seismic capacity of massive vertical type breakwaters which have intensively been deployed along the coast of South Korea over the last two decades, we carry out the preliminary numerical simulation against the PoHang, GyeongJu, Hachinohe 1, Hachinohe 2, Ofunato, and artificial seismic waves based on the measured time series of ground acceleration. Numerical result shows that significant sliding can be resulted in once non-negligible portion of seismic energy is shifted toward the longer period during its propagation process toward the ground surface in a form of shear wave. It is well known that during these propagation process, shear waves due to the seismic activity would be amplified, and non-negligible portion of seismic energy be shifted toward the longer period. Among these, the shift of seismic energy toward the longer period is induced by the viscosity and internal friction intrinsic in the soil. On the other hand, the amplification of shear waves can be attributed to the fact that the shear modulus is getting smaller toward the ground surface following the descending effective stress toward the ground surface. And the weakened intensity of soil as the number of attacking shear waves are accumulated can also contribute these phenomenon (Das, 1993). In this rationale, we constitute the numerical model using the model by Hardin and Drnevich (1972) for the weakened shear modulus as shear waves go on, and shear wave equation, in the numerical integration of which $Newmark-{\beta}$ method and Modified Newton-Raphson method are evoked to take nonlinear stress-strain relationship into account. It is shown that the numerical model proposed in this study could duplicate the well known features of seismic shear waves such as that a great deal of probability mass is shifted toward the larger amplitude and longer period when shear waves propagate toward the ground surface.

• Journal of Life Science
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• v.26 no.4
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• pp.460-467
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• 2016

A filamentous cyanobacterium, Limnothrix sp. KNUA012, was axenically isolated from a freshwater bloom sample in Lake Hapcheon, Hapcheon-gun, Gyeongsangnam-do, Korea. Its morphological and molecular characteristics led to identification of the isolate as a member of the genus Limnothrix. Maximal growth was attained when the culture was incubated at 25℃. Analysis of its lipid composition revealed that strain KNUA012 could autotrophically synthesize alkanes, such as pentadecane (C₁₅H₃₂) and heptadecane (C₁₇H₃₆), which can be directly used as fuel without requiring a transesterification step. Two genes involved in alkane biosynthesis－an acyl-acyl carrier protein reductase and an aldehyde decarbonylase－were present in this cyanobacterium. Some common algal biodiesel constituents－myristoleic acid (C_14:1), palmitic acid (C_16:0), and palmitoleic acid (C_16:1)－were produced by strain KNUA012 as its major fatty acids. A proximate analysis showed that the volatile matter content was 86.0% and an ultimate analysis indicated that the higher heating value was 19.8 MJ kg⁻¹. The isolate also autotrophically produced 21.4 mg g⁻¹ phycocyanin－a high-value antioxidant compound. Therefore, Limnothrix sp. KNUA012 appears to show promise for application in cost-effective production of microalga-based biofuels and biomass feedstock over crop plants.

• Journal of Mushroom
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• v.14 no.4
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• pp.202-206
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• 2016

Oyster mushrooms are widely cultivated and consumed in Korea. P. ostreatus 'Suhan(ASI 2504)' is an ideal cultivar for mushroom farmers due to its dark pileus and thick stipe; however, as it is very sensitive to environmental conditions, an alternative cultivar is required. To develop a new cultivar, parental strains 'Suhan(ASI 2504)' and 'ASI 0665 (Heuktari)' were selected from various collected strains according to morphological characteristics. P. ostreatus 'Soltari' was developed by DiMon crossing between the dikaryotic strain 'Suhan' and the monokaryotic strain derived from 'Heuktari'. Thirty-eight of the 100 crossed strains were selected following analysis of mitochondrial genetic characteristics, and 'Soltari' was ultimately selected by continuous cultivation tests. The mitochondrial DNA profile of 'Soltari' was found to be the same as that of 'Heuktari, and a nuclear DNA profile of 'Soltari' was similar as those of the parental strains, 'Suhan' and 'Heuktari.' 'Soltari' mycelium grows adequately in moderate to high temperatures of $12-20^{\circ}C$, although its optimum temperature was found to be $30^{\circ}C$. Fruiting body production per 1.1-L cultivation bottle was approximately 158.8 g. Its stipe length and thickness were comparable to those of diameter and thickness were somewhat lower (42.72 vs. 51.33 mm and 18.18 vs. 22.46 mm, respectively). 'Soltari' was found to be more resistant to high $CO_2$ atmosphere than 'Suhan', and the color of the pileus of 'Soltari' was dark gray at high temperature. Therefore, it is suggested that this new cultivar 'Soltari' is a good alternative cultivar and will contribute to energy saving in oyster mushroom farms.

• Journal of Life Science
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• v.26 no.10
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• pp.1121-1129
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• 2016

High-molecular-weight glutenin subunits (HMW-GSs) are extremely important determinants of the functional properties of wheat dough. Transgenic rice plants containing a wheat TaGlu-Ax1 gene encoding a HMG-GS were produced from the Korean wheat cultivar ‘Jokyeong’ and used to enhance the bread-making quality of rice dough using the Agrobacterium-mediated co-transformation method. Two expression cassettes with separate DNA fragments containing only TaGlu-Ax1 and hygromycin phosphotransferase II (HPTII) resistance genes were introduced separately into the Agrobacterium tumefaciens EHA105 strain for co-infection. Rice calli were infected with each EHA105 strain harboring TaGlu-Ax1 or HPTII at a 3:1 ratio of TaGlu-Ax1 and HPTII. Among 210 hygromycin-resistant T₀ plants, 20 transgenic lines harboring both the TaGlu-Ax1 and HPTII genes in the rice genome were obtained. The integration of the TaGlu-Ax1 gene into the rice genome was reconfirmed by Southern blot analysis. The transcripts and proteins of the wheat TaGlu-Ax1 were stably expressed in rice T₁ seeds. Finally, the marker-free plants harboring only the TaGlu-Ax1 gene were successfully screened in the T₁ generation. There were no morphological differences between the wild-type and marker-free transgenic plants. The quality of only one HMW-GS (TaGlu-Ax1) was unsuitable for bread making using transgenic rice dough. Greater numbers and combinations of HMW and LMW-GSs and gliadins of wheat are required to further improve the processing qualities of rice dough. TaGlu-Ax1 marker-free transgenic plants could provide good materials to make transgenic rice with improved bread-making qualities.