• Journal of Soil and Groundwater Environment
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• v.26 no.6
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• pp.95-105
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• 2021

Extensive groundwater abstraction has been recognized as one of the major challenges in management of coastal groundwater. The purpose of this study was to assess potential changes of groundwater distribution of northeastern Jeju Island over 10-year duration, where brackish water have been actively developed. To quantitatively estimate the coastal groundwater resources, numerical simulations using three-dimensional finite-difference density-dependent flow models were performed to describe spatial distribution of the groundwater in the aquifer under various pumping and recharge scenarios. The simulation results showed different spatial distribution of freshwater, brackish, and saline groundwater at varying seawater concentration from 10 to 90%. Volumetric analysis was also performed using three-dimensional concentration distribution of groundwater to calculate the volume of fresh, brackish, and saline groundwater below sea level. Based on the volumetric analysis, a quantitative analysis of future seawater intrusion vulnerability was performed using the volume-based vulnerability index adopted from the existing analytical approaches. The result showed that decrease in recharge can exacerbate vulnerability of coastal groundwater resources by inducing broader saline area as well as increasing brackish water volume of unconfined aquifers.

• Investigative Magnetic Resonance Imaging
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• v.2 no.1
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• pp.58-66
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• 1998

Purpose : This paper introduces a new three dimensional magnetic Resonance Image classification which is based on Mar kov Random Field-Gibbs Random Field with a line model. Material and Methods : The performance of the Gibbs Classifier over a statistically heterogeneous image can be improved if the local stationary regions in the image are disassociated from each other through the mechanism of the interaction parameters defined at the local neighborhood level. This usually involves the construction of a line model for the image. In this paper we construct a line model for multisignature images based on the differential of the image which can provide an a priori estimate of the unobservable line field, which may lie in regions with significantly different statistics. the line model estimated from the original image data can in turn be used to alter the values of the interaction parameters of the Gibbs Classifier. Results : MRF-Gibbs classifier for volumetric MR images is developed under the condition that the domain of the image classification is $E^{3}$ space rather thatn the conventional $E^{2}$ space. Compared to context free classification, MRF-Gibbs classifier performed better in homogeneous and along boundaries since contextual information is used during the classification. Conclusion : We construct a line model for multisignature, multidimensional image and derive the interaction parameter for determining the energy function of MRF-Gibbs classifier.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.562-568
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• 1999

The model using homogenization technique based on energy concept for the prediction of the failure criterion of staple fiber mixed soil was developed to increase the practice and the application of staple fiber as a reinforcement for improving soft ground and agrictural structures. Parameters of the model are aspect ration and volumetric ocntnet of fiber, cohesion and internal friction angle of soil, adhesiion intercept of soil and fiber. It is judged that the model developed in this study is applicable to the soil composed of clay, silt and sand mixed by linear types of fiber such as steel bar, steel fiber , natural fiber etc..

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.2
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• pp.86-92
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• 2000

The model using homogenization technique based on energy concept for the prediction of the failure criterion of staple fiber mixed soil was developed to increase the practice and the application of staple fiber as a reinforcement for improving soft ground. Parameters of the model are aspect ratio and volumetric content of fiber, cohesion and internal friction angle of soil, adhesion intercept and interface friction angle of soil and fiber. It is considered that the model developed in this study is applicable to the soil composed of clay, silt and sand mixed by thread types of fiber such as steel bar, steel fiber, natural fiber etc.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.521-529
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• 2002

We have recently proposed the new concept of a phase-measuring volumetric interferometer that enables us to accurately measure the xyz-coordinates of the probe without metrology frames. The interferometer is composed of a movable target and a fixed photo-detector array. The target is made of point diffraction sources to emit two spherical wavefronts, whose interference is monitored by an array of photo-detectors. Phase shifting is applied to obtain the precise phase values of the photo-detectors. Then the measured phases are fitted to a geometric model of multilateration so as to determine the xyz-location of the target by minimizing least square errors. The proposed interferometer has been designed and built with a volumetric uncertainty of less than 1.0 $\mu\textrm{m}$ within a cubic working volume of side 120 mm. Here, in this paper, we also present error sources, an evaluated uncertainty, and test results from the prototype system. The self-calibration of two-dimensional precision metrology stages is applied to test the performance of the interferometer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.217-229
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• 1994

A probabilistic method was employed to compare the prediction accuracy of axial and volumetric strains of Lade's double surface model with that of single surface model. Several experiments were conducted to examine the variabilities of soil parameters for two models using Back-ma river sand. Mean values and standard deviations of soil parameters obtained from experimental data were used for the evaluation of the uncertainty of analyzed strains by the first order approximation. It is shown that the variabilities of parameters in the single surface model are more consistent than those of the double surface model. However, in the accuracy of axial strain by probabilistic analysis, double surface model is more stable than single surface model. It is also shown that two models are excellent in view of the accuracy of the volumetric strain. The method given in this paper may be effectively utilized to estimate the constitutive model because other results of the comparison of two models coincide with those of this paper.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.115-121
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• 2010

To evaluate the engineering characteristics of aggregate base materials, cyclic triaxial, CBR and permeability tests were performed for 15 samples. The CBR values of aggregate base materials have wide range from 32 to 110(average 81) and the amount of swelling in submerged conditions has below 0.04mm. The Modulus of aggregate base materials were significantly affected by volumetric stress, linear volumetric model was best for fitting. The modulus of aggregate base materials were determined within range of 100MPa~600MPa, 80~270 and 0.1~0.6 for model coefficient $k_1$ and $k_2$ respectively. The empirical correlation model was suggested that prediction the modulus from the basic properties obtained from particle size distribution test and compaction test. The coefficient of determination of the proposed correlation model was 0.423 for model coefficient $k_1$, 0.920 for model coefficient $k_2$ and 0.872 for modulus with stress level.

• Clean Technology
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• v.19 no.3
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• pp.306-312
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• 2013

We investigated the effects of the concentration of carbon dioxide on the char-$CO_2$ gasification reaction under isothermal conditions of $850^{\circ}C$ using the Drayton coal. Potassium carbonate was used to improve the low-temperature gasification reactivity. The enhancement of carbon dioxide concentration increased the gasification rate of char, while gasification rate reached a saturated value at the concentration of 70%. The best $CO_2$ concentration for gasification is determined to be 70%. We compared the shrinking core model (SCM), volumetric reaction model (VRM) and modified volumetric reaction model (MVRM) of the gas-solid reaction models. The correlation coefficient values, by linear regression, of SCM are higher than that of VRM at low concentration. While the correlation coefficients values of VRM are higher than that of SCM at high concentration. The correlation coefficient values of MVRM are the highest than other models at all concentration.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.80-85
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• 2014

High-volume low-speed (HVLS) fans are one category of ceiling fan installed in large enclosings such as warehouses, large barns and health clubs in order to generate comfortable air circulation. As a rotary blade, aerodynamic performance of a HVLS fan is predominantly related to its airfoil(s), and the pitch and twist angles. This paper first, investigates the effects of airfoil on the performances of three different HVLS fans with NACA 5414, 6413 and 7415 airfoils. The fans have six untwisted blades with the diameter of 6 m and rotate at 60 RPM. The blades pitch angels are $12^{\circ}$, $12^{\circ}$ and $13^{\circ}$, respectively. The results are presented in the form of the aerodynamic forces and moments, volumetric flow rate and streamlines. Regarding the volumetric flow of air, the results show that the model with NACA 7415 has the best performance. Hence, two other HVLS fans with the same airfoil but, with four and five blades are studied in order to investigate the effects of number of blades. From the point of view of air circulation still the six-bladed fan is the best one; however, the five-bladed fan is more efficient in power consumption.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.6
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• pp.631-637
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• 2013

The characteristics of involute gear pump with eccentric gap between gear tip and housing have been studied in terms of volumetric flow rate and/or flow efficiency. The analysis has been done with FLUENT/R-13 employing with k-e model for the turbulent flow under the given conditions of rotational velocity, gap distance and outlet pressure. The effect of parameters continues to be shown for the eccentric gear as same as for the concentric gear such that the volumetric flow rate (volumetric efficiency) increases as the increases of rotational velocity and decrease of gap distance and of outlet pressure. In the meantime, the shape of pressure build-up appears to be exponentially increase as gap distance decreases at upstream position. The pressure is rapidly developing in the upstream and remains almost constant thereafter in the downstream of circumferential flow path. This typical characteristics becomes more profound as eccentricity increases. The pump performance for the eccentric gear pump with minimum gap distance shows better than its concentric counterpart. However, it shows not for the concentric pump with minimum gap distance. Therefore, the gap reduction due to eccentricity may be positive for pump performance.