• Journal of the Korea Institute of Building Construction
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• v.19 no.6
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• pp.477-484
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• 2019

The purpose of this study is to present basic data for developing concrete with EMP shielding as the structure materials when constructing an EMP shielded building structure. In order to use metal-based recycled aggregates with excellent conductivity and easy procurement for EMP shielding concrete, an evaluation of the stability evaluation and EMP shielding performance was performed. Through the stability evaluation, it was found that the coarse aggregate stability criterion was satisfied, but the oxidized slag did not satisfy the fine aggregate stability criterion, the oxidized slag is not satisfied. In addition, as a result of fresh concrete, the workability is increased and the air volume is decreased. The compressive strength is increased due to the high density and coarse granularity of the recycled aggregates, which increased the cement paste and adhesion, thereby increasing the compressive strength. The results of an EMP shielding test show that aggregates with high shielding performance are electronic arc furnace(EAF) Oxidizing Slag and Cooper Slag. The shielding performance is expected to increase if the average particle size of aggregate is small or uniformly distributed.

• Journal of the Korean Geotechnical Society
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• v.36 no.10
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• pp.21-31
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• 2020

In this study, Hoek-Brown constants (m_i) were calculated through nonlinear regression analyses using the results of the triaxial compression tests for the basaltic intact rocks in Jeju Island. The relationships of the m_i with the uniaxial compressive strength (UCS), Brazilian tensile strength (BTS) and UCS/BTS of the Jeju basalts were investigated, respectively. In addition, a method that can be used in determining Hoek-Brown failure envelopes including the tensile and compressive failures of the Jeju basalts has been proposed. As results, the m_i values had no clear correlations with the UCS, BTS and UCS/BTS of the Jeju basalts, but there were two strong correlations between UCS and m_i/UCS, and between BTS and m_i/BTS of the Jeju basalts. In addition, it was found that the tensile strengths calculated by the Hoek-Brown failure criterion underestimate the tensile strengths of the Jeju basalts through the relationship between the m_i and UCS/BTS of the Jeju basalts. The method presented in this study is considered to be useful in determining the Hoek-Brown failure envelope for the tensile and compressive failures of the Jeju basalts.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.13-22
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• 2007

This study was carried out to scrutinize possibility of manufacturing pitch pine (Pinus rigida) glued laminated timber in order to add values of pitch pine trees. Also, it was investigated to improve bending performance of pitch pine glulam. Pitch pine was imported as one of major plantation species in Korean peninsula. Machine stress rated grades of pitch pine lumber mostly ranged between E7 and E9. which grades were more or less inferior to producing high quality glulam. However, the adhesive properties between pitch pine and pitch pine, and between pitch pine and Japanese larch (Larix kaempferi Carr.), such as shear bond strength, wood failure rate and de-lamination rate of bonded layer submerged in cold and boiling water, were higher than Korean Standard criteria. These properties are essential for manufacturing glulam with single species or multiple species. The modulus of rupture (MOR) of pitch pine glulam exceeded the criterion of Korean Standard for glulam strength grade but modulus of elasticity (MOE) was lower than the criterion. On the other hand, the bending performances (MOR and MOE) were improved 20 percent by mixing with Japanese larch laminar. It is effective to arrange higher quality Japanese larch laminar at the outer layer of glulam for improving bending performances. In conclusion, it is possible to use low quality pitch pine as laminar of structural glulam for adding values of pitch pine.

• Korean Journal of Poultry Science
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• v.15 no.3
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• pp.219-227
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• 1988

This experiment was carried out to evaluate biological availability of Ca and P in 4 different sources of tricalcium phosphate in young chicks. One hundred and twenty five-day-old male Single Comb White Leghorn chicks (10 treatments$\times$3replication$\times$4chicks) were used in trial 1 and 2, respectively, for 12 days of feeding period. Trial I was to evaluate the availability of phosphorus in the supplements, Standard purified diets were prepared to supply 0.07, 0.14 and 0.21％P using a mixture (1 : 1) of NaH$_2$PO$_4$ and KH$_2$PO$_4$ as the reference Phosphorus sources. Bone breaking strength of the tibia determeined by an Instron instrument appeared inadequate to be used as a criterion due to very high variations of the measurement within a treatment. Thus, tibia bone ash content was utilized as a criterion to evaluate th biological avilability of phosphorus in the supplements. The levels of the biological availability of the four different sources of dicalcium phoshate were 77.1, 91.0, 96.4 and 95.5％, respectively, and those of the three tricalcium phosphate sources were 94.1, 95.0 and 99.5％ , respectively. Trial 2 was to determeine the levels of Ca biologically available in the supplements. Standard purified diets were made to supply 0.2, 0.3 and 0.4％ Ca using CaCo$_3$ as the reference calcium source. When bone ash content was utilized as a criterion for the availability, the levels of calcium biologically available to the chicks were 78.3, 234.1, 87.6 and 244.5％, respectively, for the 4 different sources of dicalcium phosphate and 99.5, 84.0 and 101.5％ , respectively, for the 3 different sources of tricalcium phosphate. The observation that two calcium sources appeared to be utilized with an unusual efficiency can hardly be explained at this moment. When they were revaluated on the basis of body weight gain, the availabilities of the four sources of dicalcium phosphate were 89.2, 58.2, 104.1 and 103.1％ and of the three tricalcium phosphate were 112.6, 106.0 and 96.3％ , respectively.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.4
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• pp.369-376
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• 2003

In this paper, a nonlinear structural analysis for the composite structure composed of the spent nuclear fuel disposal canister and the 50㎝ thick bentonite buffer is carried out to predict the collapse of the canister while the horizontal symmetric sudden rock movement of 10㎝ is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Elastoplastic material model is adopted. Drucket-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the canister(cast iron, copper). Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffet, the canister structure still endures elastic small strains and stresses below the yield strength. Hence, the 50㎝ thick bentonite buffet can protect the canister safely against the 10㎝ sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the canister structure due to the shear deformation of the bentonite buffer.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.597-610
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• 2022

Knowledge of the failure behavior of friction materials considering their intermediate principal stress is related to an understanding of situations where these materials might be used: for example, the stability of deep-seated boreholes and fault slip analysis. This study designed equipment for physically implementing true triaxial compression and used it to assess specimens of plaster, a friction material. The material's mechanical behaviors are discussed based on the results. The applicability of the 3D failure criteria are also reviewed. The tested specimens were molded cuboids of width, length, and height 52, 52, and 104 mm, respectively. A total of 24 true triaxial compression tests were performed under various combinations of 𝜎₃ and 𝜎₂ conditions. Conventional uniaxial and triaxial compression tests were employed to estimate the mechanical properties of the plaster for use as parameters for 3D failure criteria. Examining the stress-strain relations of the plaster materials showed that a large difference between the intermediate principal stress and the minimum principal stress indicated strong brittle behavior. The mechanical behavior of the plaster used here reflects the change of intermediate principal stress. Nonlinear multiple regression analysis on the test data in the principal space showed that the modified Wiebols-Cook failure criterion and the modified Lade failure criterion were the most suitable 3D failure criteria for the tested plaster.

• International Journal of Computer Science & Network Security
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• v.22 no.12
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• pp.63-70
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• 2022

The essence of the definition of "tolerance" is analyzed. Motivational, knowledge and behavioral criteria for tolerance of future teachers are highlighted. Indicators of the motivational criterion are the formation of value orientations, motivational orientation, and the development of empathy. Originality and productivity of thoughts and judgments, tact of dialogue, pedagogical ethics and tact are confirmed as indicators of the knowledge criterion. The behavioral criterion includes social activity as a life position, emotional and volitional endurance, and self-control of one's own position. The formation of tolerance is influenced by a number of factors: the social environment, the information society, existing stereotypes and ideas in society, the system of education and relationships between people, and the system of values. The main factors that contribute to the education of tolerance in future teachers are highlighted. Analyzing the structure of tolerance, it is necessary to distinguish the following functions of tolerance: - motivational (determines the composition and strength of motivation for social activity and behavior, promotes the development of life experience, because it allows the individual to accept other points of view and vision of the solution; - informational (understanding the situation, the personality of another person); - regulatory (tolerance has a close connection with the strong - willed qualities of a person: endurance, selfcontrol, self-regulation, which were formed in the process of Education); - adaptive (allows the individual to develop in the process of joint activity a positive, emotional, stable attitude to the activity itself, which the individual carries out, to the object and subject of joint relations). The implementation of pedagogical functions in the information society: educational, organizational, predictive, informational, communicative, controlling, etc. provides grounds to consider pedagogical tolerance as an integrative personal quality of a representative of any profession in the field of "person-person". The positions that should become conditions for the formation of tolerance of the future teacher in the information society are listed.

• Geomechanics and Engineering
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• v.22 no.3
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• pp.255-264
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• 2020

With the ongoing development of deep mining of coal resources, some coal mine dynamic disasters have exhibited characteristics of both coal-gas outbursts and rockbursts. Therefore, research is required on the mechanism of rockburst-outburst coupling disaster. In this study, the failure characteristics of coal-rock combination structures were investigated using lab-scale physical simulation experiments. The energy criterion of the rockburst-outburst coupling disaster was obtained, and the mechanism of the disaster induced by the gas-solid coupling instability of the coal-rock combination structure was determined. The experimental results indicate that the damage of the coal-rock structure is significantly different from that of a coal body. The influence of the coal-rock structure should be considered in the study of rockburst-outburst coupling disaster. The deformation degree of the roof is controlled by the more significant main role of the gas pressure and the difference in the strength between the rock body and the coal body. The outburst holes and spall characteristics of the coal body after the failure of the coal-rock structure are strongly affected by the difference in strength between the roof and the coal body. The research results provide an in-depth understanding of the mechanism of rockburst-outburst coupling disasters in deep mining.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.20-28
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• 2004

For the prediction on the onset of oblique shock wave-induced vortex breakdown, computational studies on the Oblique Shock wave/Vortex Interaction (OSVI) are conducted and compared with both experimental results and analytic mode1. A Shock-stable numerical scheme, the Roe scheme with Mach number-based function (RoeM), and a two-equation eddy viscosity-transport approach arc used for three-dimensional turbulent flow computations. The computational configuration is identical to available experiment, and we attempt to ascertain the effect of parameters such as a vortex strength, streamwise velocity deficit, and shock strength at a freestream Mach number of 2.49. Numerical simulations using the k-w SST turbulence model and suitably modeled vortex profiles are able to accurately reproduce many fine features through a direct comparison with experimental observations. The present computational approach to determine the criterion on the onset of oblique shock wave-induced vortex breakdown is found to be in good agreement with both the experimental result and the analytic prediction.

• Tunnel and Underground Space
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• v.26 no.2
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• pp.68-86
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• 2016

Understanding the frictional properties of rock discontinuities is crucial to ensure the stability of underground structures. In particular, the frictional behavior at depth depends on the complex interaction among mechanical, hydraulic, thermal and chemical characteristics and their coupled effects. In this study, a series of shear tests were carried out in a triaxial compression chamber to investigate the shearing behavior of saw-cut granite surface and rough shear surface of synthetic rocks. The test results were analyzed using Coulomb's shear strength criterion. The frictional behavior of saw-cut granite surface showed little variation at different confining, water pressures and temperature conditions, however in case of synthetic rocks, the frictional behavior showed different trend depending on normal stress level. In addition, the variation of stiffness and dilation at different testing conditions were analyzed, and the stiffness and dilation showed little variation at different water pressures and temperature conditions.