• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.39-45
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• 2006

Analysis of the internal state of the blast furnace is needed to predict and control the operating condition. Especially, it is important to develop modeling of blast furnace for predicting cohesive zone because shape of cohesive zone influences overall operating condition of blast furnace such as gas flow, chemical reactions and temperature. because many previous blast furnace models assumed cohesive zone to be fixed, they can't evaluate change of cohesive zone shape by operation condition such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace process. In this model, cohesive zone is changed by solid temperature range, FVM is used for numerical simulation. To find location of cohesive zone whole calculation procedure is iterated Until cohesive zone is converged. Through this approach, shape of cohesive zone, velocity, composition and temperature within the furnace are predicted by model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.401-407
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• 2014

In this paper, the effect of cohesive laws on the finite element analysis of crack propagation using cohesive elements is investigated through three-point bending and double cantilever beam problems. The cohesive elements are implemented into ABAQUS/Standard user subroutines(UEL), and the shape of cohesive law is varied by changing parameters in polynomial functions of cohesive traction-separation relations. In particular, crack propagation behaviors are studied by comparing load-displacement curves of the analysis models which have different shapes of cohesive laws with the same values of fracture energy and cohesive strength. Furthermore, the influence of the element size on crack propagation is discussed in this study.

• Korean Journal of Ecology and Environment
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• v.44 no.1
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• pp.66-74
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• 2011

This numerical study aims to investigate the effect of cohesive sediment on turbulence structure due to density stratification. The transport model for cohesive sediment incorporated with flocculation model has been selected and calculates the concentration, fluid momentum, and turbulence. From the model results, it is known that suspension of sediment decreases turbulence intensity. It is also found that cohesive sediment has a relatively weak effect on turbulence damping compared to noncohesive sediment. The low settling velocity and more suspension of cohesive sediment are considered to be mechanisms of this behavior. Richardson number determined with results of this study quantitatively shows that cohesive sediment causes less stable density stratification condition and, as a result, the turbulence structure is less damped compared to the case of noncohesive sediment.

• Advances in aircraft and spacecraft science
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• v.1 no.2
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• pp.177-196
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• 2014

A theoretical exploration for determining the characteristic length of the cohesive zone for a double cantilever beam (DCB) specimen under mode I loading was conducted. Two traction-separation laws were studied: (i) a law with only a linear elastic stage from zero to full traction strength; and (ii) a bilinear traction law illustrating a progressive softening stage. Two analytical solutions were derived for the first law, which fit well into two existing solution groups. A transcendental equation was derived for the bilinear traction law, and a graphical method was presented to identify the resultant cohesive zone length. The study using the bilinear traction law enabled the theoretical investigation of the individual effects of cohesive law parameters (i.e., strength, stiffness, and fracture energy) on the cohesive zone length. Correlations between the theoretical and finite element (FE) results were assessed. Effects of traction law parameters on the cohesive zone length were discussed.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.409-415
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• 2009

Kozeny-Carman equation has been generally applied to prediction of permeability for soil. The Kozeny-Carman equation has indicated fairly good results in prediction of sandy soils, but it is known that the equation is not appropriate for fine-grained soils such as cohesive soils. Therefore, a theoretical equation based on Kozeny-Carman equation is proposed to predict of permeability for cohesive soils in this paper. To develop the theoretical equation, soil properties of cohesive soil existed in the coastal areas and compacted cohesive soil used for the core of a dam were investigated and analyzed. As the results of this limited study, the most related factors between soil properties and permeability were #200 passing percentage for compacted cohesive soil, and clay content for cohesive soil at the coast areas.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.911-918
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• 2014

In this paper, a selective activation strategy of cohesive elements using user subroutine UMPC was studied as an efficient solution for the added compliance problem in cohesive zone model crack propagation analyses. The cohesive elements were inserted between every bulk elements in region where cracks were expected to initiate and propagate, but initially not activated by tying the cohesive nodes using multi-point constraints. During analyses, the cohesive elements for which specified criterion was met were selectively activated by releasing the constraints. The effect of initial cohesive stiffness and the release criterion on the crack propagation behavior was carefully investigated.

• Journal of the Korean Society of Combustion
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• v.14 no.4
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• pp.1-6
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• 2009

Analysis of the internal state of the blast furnace is necessary to predict and to control the operating conditions. Especially, it is important to develop models of the blast furnace to predict the cohesive zone because shape of the cohesive zone influences overall operating conditions of blast furnace such as gas flow, chemical reactions and temperature. Because many previous blast furnace models have assumed cohesive zone to be fixed, it was not possible to evaluate the shape change of cohesive zone in relation with operating conditions such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace processes. In this model, cohesive zone is determined by the solid temperature. Finite volume method is employed for numerical simulation. To find location of the cohesive zone, entire calculation procedure is iterated until converged. Through this approach, shape of the cohesive zone, velocity and temperature within the furnace are predicted from the model.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1275-1284
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• 2021

This paper presents a machine learning technique applied to prediction of time-dependent local scour around bridge piers in both non-cohesive and cohesive beds. The support vector machines (SVM), which is known to be free from overfitting, is used. The time-dependent scour depths are expressed by 7 and 9 variables for the non-cohesive and cohesive beds, respectively. The SVM models are trained and validated with time series data from different sources of experiments. Resulting Mean Absolute Percentage Error (MAPE) indicates that the models are trained and validated properly. Comparisons are made with the results from Choi and Choi's formula and Scour Rate in Cohesive Soils (SRICOS) method by Briaud et al., as well as measured data. This study reveals that the SVM is capable of predicting time-dependent local scour in both non-cohesive and cohesive beds under the condition that sufficient data of good quality are provided.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2038-2043
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• 2007

Analysis of the internal state of the blast furnace is needed to predict and control the operating condition. Especially, it is important to develop modeling of blast furnace for predicting cohesive zone because shape of cohesive zone influences on overall operating condition of blast furnace such as gas flow, temperature distribution and chemical reactions. Because many previous blast furnace models assumed cohesive zone to be fixed, they can't evaluate change of cohesive zone shape by operation condition such as PCR, blast condition and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace process using the general purpose-simulation code. And Porous media is assumed for the gas flow and the potential flow for the solid flow. Velocity, pressure and temperature distribution for gas and solid are displayed as the simulation results. The cohesive zones are figured in 3 different operating conditions.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.3
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• pp.89-95
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• 2010

There is the freezing method as one of the ground improvement methods for excavating an underground tunnel, and due to its improved reliability, recently construction cases of applying this method into sandy soil grounds as well as cohesive soil grounds of cities have been reported. But, applying the freezing method into cohesive soil grounds could bring concerns of the expansion of the whole ground and the settlements from thawing of ground. In this study, the deformation strength characteristics of cohesive soil which received freezing and thawing hysteresis were examined using the sample collected from the site of cohesive soil ground applied with the freezing method and its structural characteristics were analyzed using an electronic microscope. And, the test with cohesive soil reconstituted from cohesive soil which received freezing and thawing hysteresis was carried out and its result was analyzed comparatively. The result of this test showed that the structure of natural clay was significantly changed due to freezing and thawing hysteresis.