• Magazine of the Korea Concrete Institute
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• v.17 no.4 s.87
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• pp.34-40
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• 2005

• The Korean Journal of Applied Statistics
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• v.21 no.1
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• pp.109-123
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• 2008

Many small area estimation methods have been suggested. Also for the comparison of the estimation methods, model diagnostic checking techniques have been studied. Almost all of the small area estimators were developed by minimizing MSE(Mean square error) and so the MSE is the well-known comparison criterion for superiority. In this paper we suggested a new small area estimator based on minimizing MSPE(Mean square percentage error) which is recently re-highlighted. Also we compared the new suggested estimator with the estimators explained in Shin et al. (2007) using MSE, MSPE and other diagnostic checking criteria.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.289-294
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• 2011

The installation of joint is to prevent random cracking due to drying shrinkage stress of concrete slab. However contraction joint spacing is empirically implemented into slab constructions without detail calculation based on quantitative criteria. In this study, shrinkage strain of concrete due to concrete shrinkage stress was measured to suggest joint spacing based on the study results. The test environmental conditions were applied temperature of $15^{\circ}C$ and relative humidity of 60%. The design compressive strength used was 30 MPa and 40 MPa, which are currently used in concrete slab designs. The drying shrinkage test result was applied to drying shrinkage models (ACI 209R, CEB MC 90, B3, GL 2000 and Sakata). The results showed that the most appropriate model was ACI 209R model. Based on the research findings, quantitative contraction joint spacing locations were calculated.

• Magazine of the Korea Concrete Institute
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• v.6 no.4
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• pp.102-112
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• 1994

The drying shrinkage of concrete has a close relation to the water movement. Since the diffusion process of water in concrete is strongly dependent on the temperature and the pore humidity, the process is highly nonlinear phenomena. This study consists of two parts. The first is the development of a finite element program which is capable of simulating the rnoisture distri- ,bution in concrete, and the other is the estimation of the differential drying shrinkage and stress considering creep by using the modified elastic modulus due to inner temperature change and maturity. It is shown that the analytical results of this study are in good agreement with experlimental data in the literatures, and results calculated by BP-KX model. The internal stress caused by moisture distribution which was resulted from the diffusion process, was calculated :quantitatively. The tensile stress which occured in the drying outer zone mostly exceeded the tensile strength of concrete, and necessarily would result in crack formation.

• Journal of the Korea Institute of Building Construction
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• v.14 no.1
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• pp.110-117
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• 2014

The objective of this study is to investigate an effect of curing temperature on autogenous shrinkage of high strength cement mortar with 0.15 of W/B incorporating fly ash and silica fume in terms of equivalent age. The contents of fly ash and silica fume are varied from 10% to 30%. Non linear regression model applying equivalent age was used to estimate the autogenous shrinkage evolution. To obtain apparent activation energy($E_a$), setting time method by Pinto and existing method were calculated and compared respectively. Test results showed that use of silica fume increased autogenous shrinkage while use of fly ash decreased it. It was also found that poor agreements were obtained when $E_a$ by setting time was applied. But, application of existing $E_a$ resulted in a good agreement between calculated autogenous shrinkage and measured one.

• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.119-125
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• 2009

In this paper, the engineering properties and estimation of drying shrinkage of concrete incorporating fly ash (FA), blast furnace slag (BS) and cement kiln dust (CKD) were discussed. FA, BS and CKD contents ranged from 0% to 20%. Water to binder ratio (W/B) also ranged from 40 to 50 %, with a 5% interval. For estimating drying shrinkage, an exponential model proposed by the author was applied, According to results, the use of FA, BS and CKD resulted in a decrease of flowability and air contents. As expected, the use of admixtures also decreases the early age strength of concrete, while at later age, due to a pozzolanic reaction of FA and BS, the compressive strength was recovered to a value comparable with that of plain concrete. For drying shrinkage, the use of admixtures led to an increase in the drying shrinkage of concrete. The exponential model suggested by the author showed good agreement between the calculated and experimental values both at early age and at later age.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.367-368
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• 2007

In this paper, we propose a new de-noising algorithm for 2 dimensional image using discrete wavelet transform. The proposed algorithm consists of edge detection in spatial domain, zero-tree estimation, subband estimation, and shrinkage algorithm. The results from it shows that the denoised image which Is damaged by 20% gaussian noise has 28dB quality for the original one.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.343-350
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• 2014

A probabilistic construction stage analysis using the Monte Carlo Simulation was performed to address the effects of uncertainty regarding the material properties, environmental factors, and applied forces. In the previous research, creep and shrinkage were assumed to be completely independent random variables. However, because of the common influencing factors in the material models for the creep and shrinkage estimation, strong correlation between creep and shrinkage can be presumed. In this paper, an Monte Carlo Simulation using CEB-FIB creep and shrinkage equations were performed to actually evaluate the correlation coefficient between two phenomena, and then another Monte Carlo Simulation to evaluate the statistical properties of axial strain affected by partially correlated random variables including the material properties, environmental factors, and applied forces. The results of Monte Carlo Simulation were compared with measured strains of a column on a first story in a 58-story building. Comparison indicated that the variation due to the uncertainty related with the material properties were most severe. And measured strains was within the range of mean+standard deviation.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.581-584
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• 2008

In this study, it is willing to present that fundamental data for proposing quantitatively shrinkage cracking evaluation method such as plat-ring type restrained test method. To examine suitable size of specimen of plat-ring type restrained test method, Evaluated concrete about restrained shrinkage crack properties of numerical analysis of 3D solid element using the MIDAS program, drying shrinkage deformation, restrained shrinkage stress, crack area and crack point with inside ring diameter of specimen in 100mm, 150mm, 200mm and high of Specimen in 30mm, 50mm after curing in condition of constant temperature and usual habit of temperature 20${\pm}$3$^{\circ}$C, humidity 60${\pm}$5%. As a result, it was available about suitable estimation with inside ring diameter of specimen in more than 150mm and high of Specimen in 50mm. Hereafter, it is considered that the study concerning environmental condition and mixing factor in plat-ring type restrained test method is need.

• The Journal of the Acoustical Society of Korea
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• v.42 no.4
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• pp.305-312
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• 2023

Physics-Informed Neural Network (PINN) is used to invert bubble size distributions from attenuation losses. By considering a linear system for the bubble population inversion, Adaptive Learned Iterative Shrinkage Thresholding Algorithm (Ada-LISTA), which has been solved linear systems in image processing, is used as a neural network architecture in PINN. Furthermore, a regularization based on the linear system is added to a loss function of PINN and it makes a PINN have better generalization by a solution satisfying the bubble physics. To evaluate an uncertainty of bubble estimation, deep ensemble is adopted. 20 Ada-LISTAs with different initial values are trained using the same training dataset. During test with attenuation losses different from those in the training dataset, the bubble size distribution and corresponding uncertainty are indicated by average and variance of 20 estimations, respectively. Deep ensemble Ada-LISTA demonstrate superior performance in inverting bubble size distributions than the conventional convex optimization solver of CVX.