• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.609-617
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• 2008

Water pipes are supposed to deliver the predetermined demand safely to a certain point in water distribution system. However, pipe burst or crack can be happened due to so many reasons such as the water hammer, natural pipe ageing, external impact force, soil condition, and various environments of pipe installation. In the present study, the reliability model which can calculate the probability of pipe breakage was developed regarding unsteady effect such as water hammer. For the reliability model, reliability function was formulated by Barlow formula. AFDA method was applied to calculate the probability of pipe breakage. It was found that the statistical distribution for internal pressure among the random variables of reliability function has a good agreement with the Gumbel distribution after unsteady analysis was performed. Using the present model, the probability of pipe breakage was quantitatively calculated according to random variables such as the pipe diameter, thickness, allowable stress, and internal pressure. Furthermore, it was found that unsteady effect significantly increases the probability of pipe breakage. If this reliability model is used for the design of water distribution system, safe and economical design can be accomplished. And it also can be effectively used for the management and maintenance of water distribution system.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.107-115
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• 2015

The objective of the this study is to find the breakage index and changes in permeability of Bottom ash from thermoelectric power plants in Korea. Bottom ash was crushed by compaction according to compaction energy from 0 to $1661.4\;kN/m^2$. The particle size distribution was estimated by sieve analysis. The various breakage indexes were used for analyzing the change in particle size distribution and effect of compaction energy. In the result, breakage indexes were increased as compaction energy and initial upper 4.75 mm diameter ratio, but values and tendencies of breakage indexes appeared in different as calculation method of breakage indexes. The coefficient of permeability was decreased with particle breakage, but decreasing ratio of permeability was very small. Bottom ash has a higher permeability than the weathered soil and it is considered high usability as a permeable materials.

• Geomechanics and Engineering
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• v.11 no.5
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• pp.639-655
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• 2016

The effect of particle breakage and intermediate principal stress ratio on the behaviour of crushable granular assemblies under true triaxial stress conditions is studied using the discrete element method. Numerical results show that the increase of intermediate principal stress ratio $b(b=({\sigma}_2-{\sigma}_3)/({\sigma}_1-{\sigma}_3))$ results in the increase of dilatancy at low confining pressures but the decrease of dilatancy at high confining pressures, which stems from the distinct increasing compaction caused by breakage with b. The influence of b on the evolution of the peak apparent friction angle is also weakened by particle breakage. For low relative breakage, the relationship between the peak apparent friction angle and b is close to the Lade-Duncan failure model, whereas it conforms to the Matsuoka-Nakai failure model for high relative breakage. In addition, the increasing tendency of relative breakage, calculated based on a fractal particle size distribution with the fractal dimension being 2.5, declines with the increasing confining pressure and axial strain, which implies the existence of an ultimate graduation. Finally, the relationship between particle breakage and plastic work is found to conform to a unique hyperbolic correlation regardless of the test conditions.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.2
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• pp.70-75
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• 2006

Owing to the strike of lightning a breakage of insulator would happen. This breakage may give rise to many problems such as increment of reclosing failure, a drop for reliance and a hardship of maintenance and repair. To solve those problem, this study develop a protected equipment for insulator which is suitable to 22.9[kV] distribution line towers and is purposed to investigation for a Proper adaption, Protection efficiency of insulator and effect of adaption.

• Proceedings of the KAIS Fall Conference
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• 2006.11a
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• pp.172-175
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• 2006

Owing to the strike of lighting a breakage of insulator would happen. This breakage may give rise to many problems such as increment of reclosing failure, a drop for reliance and a hardship of maintenance and repair. To solve those problems, this study develop a protected equipment for insulator which is suitable to 22.9kV distribution line towers and is purposed to investigation for a proper adaption, protection efficiency of insulator and effect of adaption.

• Resources Recycling
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• v.29 no.3
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• pp.11-23
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• 2020

This study aims to investigate breakage and liberation characteristics of iron ore from Shinyemi mine, Jeongseon by ball mill. Parameters of breakage functions for three grade samples of iron ore were obtained using single-sized-feed breakage test and back-calculation based on nonlinear programming. The results showed that with the increase in the grade of iron ore, the breakage rate factor decrease whereas the particle size sensitivity decreases. This results from retardation of microcrack-propagation by magnetite grain in the ore. Breakage distribution analysis showed that the breakage mechanism appear to be impact fracture dominant with the increase of grade owing to the stress distribution effect by magnetite grain. Degree of liberation (DOL) increased with the increase in grade and decrease in particle size, respectively. Using the breakage function and size-DOL relationship, a model that can predict time-dependent-DOL is established. When scale-up factors from operating condition are available, the model is expected to be capable of predicting size and DOL with time in actual mining process.

• Journal of Korea Water Resources Association
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• v.52 no.5
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• pp.373-380
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• 2019

In this study, the optimum pump operation technique is suggested to decrease the damage rate of water distribution system. Pump operation system was developed to achieve the effective pump operation. Pressure sensors which can communicate with pumps are installed at the end of water distribution system. Pump operation system can control the pressure of water pump according to data sent from the pressure sensors. Therefore, water distribution system can reduce the pressure and maintain enough pressure which can supply the demand of water users. For proving effectiveness of new system, reliability model was introduced to compare the results of damage rates between the maintaining high pressure and selective pressure in water pump. Unsteady analysis was conducted with several scenarios. And the results were used to calculate the probability of pipe breakage. From the results, it was found that new pump operation system can reduce the energy usage and probability of pipe breakage by applying to pumps.

• Resources Recycling
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• v.28 no.3
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• pp.26-34
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• 2019

Due to the increasing demand of rare earth magnet for various application, it is predicted that the amount of waste rare earth magnet will increase sharply. The process of waste rare earth magnet recycling is mainly consisted of leaching and separation of rare earth element contained in the magnet. However, there is no study on the breakage characteristics of the waste rare earth magnet for production of magnet powder. Therefore, in this study, effective crushing/grinding process and breakage characteristics were investigated for waste rare earth magnet. In the case of jaw crusher, the particle size of magnet was effectively reduced without rapid oxidation. In ball mill grinding test, it was found that the grinding process was not performed properly at the early stage of grinding. Moreover, waste rare earth magnet showed very low specific rate of breakage(S) and high fraction of fine particle breakage distribution(B) compared to ordinary minerals. These results can be used as a basic data for developing crushing/grinding circuit of waste rare earth magnet.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.172-175
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• 2005

The numerical simulation is performed for the acoustic emission and the wave propagation due to fiber breakage in single fiber composite plates by the finite element transient analysis. The acoustic emission and the following wave motions from a fiber breakage under a static loading is simulated to investigate the applicability of the explicit finite element method and the equivalent volume force model as a simulation tool of wave propagation and a modeling technique of an acoustic emission. For such a simple case of the damage event under static loading, various parameters affecting the wave motion are investigated for reliable simulations of the impact damage event. The high velocity and the small wave length of the acoustic emission require a refined analysis with dense distribution of the finite element and a small time step. In order to fulfill the requirement for capturing the exact wave propagation and to cover the 3-D simulation, we utilize the parallel FE transient analysis code and the parallel computing technology.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.365-372
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• 2016

Using the computational fluid dynamics (CFD) technique, we simulated the fluid flow in a Taylor reactor considering the aggregation and breakage of particles. We calculated the population balance equation (PBE) to determine the particle-size distribution by implementing the quadrature method-of-moment (QMOM). It was used that six moments for an initial moments, the sum of Brownian kernel and turbulent kernel for aggregation kernel, and power-law kernel for breakage kernel. We predicted the final mean particle size when the particle had various initial volume fraction values. The result showed that the mean particle size and initial growth rate increased as the initial volume fraction of the particle increased.