• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.414-419
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• 2006

In this paper, the numerical results using the Mohr-Coulomb and the Duncan-Chang models, on the stresses and strains of a tunnel under a deep open-cut site and the surrounding ground, were compared with each other. The Mohr-Coulomb model produced larger values than the Duncan-Chang model in stress and displacement of tunnel and ground.

• Journal of the Korean GEO-environmental Society
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• v.19 no.12
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• pp.47-58
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• 2018

Duncan & Chang(1970) proposed the Duncan-Chang model that a linear relation of transformed stress-strain plots was reconstituted from a nonlinear relation of stress-strain curve of triaxial compression test using hyperbolic theory so as to estimate an initial tangent modulus and ultimate deviator stress for the soil specimen. Although the transformed stress-strain plots show a linear relationship theoretically, they actually show a nonlinearity at both low and high values of strain of the test. This phenomenon indicates that the stress-strain curve is not a complete form of a hyperbola. So, if linear regression analyses for the transformed stress-strain plot are performed over a full range of strain of a test, error in the estimation of their linear equations is unavoidable depending on ranges of strain with non-linearity. In order to reduce such an error, a modified regression analysis method is proposed in this study, in which linear regression analyses for transformed stress-strain plots are performed over the entire range of strain except the range the non-linearity is shown around starting and ending of the test, and then the initial tangent modulus and ultimate deviator stresses are calculated. Isotropically consolidated-drained triaxial compression tests were performed on compacted weathered soil with a modified Proctor density to obtain their model parameters. The modified regression analyses for transformed stress-strain plots were performed and analyzed results are compared with results estimated by 2 points method (Duncan et al., 1980). As a result of analyses, initial tangent moduli are about 4.0% higher and ultimate deviator stresses are about 2.9% lower than those values estimated by Duncan's 2 points method.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.291-298
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• 2019

In order to study the mechanical properties of rock salt, triaxial compression tests under different temperatures and confining pressure are carried out on rock salt specimens, the influence of temperature and confining pressure on the mechanical properties of rock salt was studied. The results show that the temperature has a deteriorative effect on the mechanical properties of rock salt. With the increase of temperature, the peak stress of rock salt decreases visibly; the plastic deformation characteristics become much obvious; the internal friction angle increases; while the cohesion strength decreases. With the increase of confining pressure, the peak stress and peak strain of rock salt will increase under the same temperature. Based on the test data, the Duncan-Chang constitutive model was modified, and the modified Duncan-Chang rock salt constitutive model considering the effect of temperature and confining pressure was established. The stress-strain curve calculated by the modified model was compared with the stress-strain curve obtained from the test. The close match between the test results and the model prediction suggests that the modified Duncan-Chang constitutive model is accurate in describing the behavior of rock slat under different confining pressure and temperature conditions.

• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.2
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• pp.21-30
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• 2005

The primary purpose of this paper is to prove a clear relationship among land use type, vegetation level and surface temperature. For this purpose, this paper presents series of spatial distribution maps of the three features obtained through the visual interpretation of digital images. The result of study tells us that the spatial distribution of the vegetation level is very similar with that of surface temperature. By analyzing the relationship between surface temperature and land use types, this study categorizes the eighteen urban land uses into 7-8 groups according to their average surface temperature. The Duncan test was conducted to categorize the land uses. The surface temperature of manufacturing related land use is the highest, semi-residential use is the next, non-residential land use is the next to the lowest, and the agricultural and forest land use is the lowest. This paper provides another strong evidence of the relationship by showing the regression result.

• Geomechanics and Engineering
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• v.10 no.1
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• pp.37-48
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• 2016

The hyperbolic stress-strain model has been shown to be valid for modeling nonlinear stress-strain behavior for rockfill materials. The Duncan-Chang nonlinear constitutive model was adopted to characterize the behavior of the modeled rockfill materials in this study. Accurately estimating the model parameters of rockfill materials is a key problem for simulating dam deformations during both the dam construction period and the dam operation period. In order to estimate model parameters, triaxial compression experiments of rockfill materials were performed. Based on a genetic algorithm, the constitutive model parameters of the rockfill material were determined from the triaxial compression experimental data. The investigation results show that the predicted strains provide satisfactory precision when compared with the observed strains and the strains forecasted by a gradient-based optimization algorithm. The effectiveness of the proposed inversion procedure of model parameters was verified by experimental investigation in a laboratory.

• Journal of the Korean Arthroscopy Society
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• v.8 no.1
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• pp.37-44
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• 2004

Purpose: To evaluate the optimal number of additional half hitches for achieving an optimal knot-holding capacity (KHC) of Lockable sliding knots. Methods: Four configurations of arthroscopic knots (Duncan loop, Field knot, Giant knot, and SMC knot) were tested for their knot-holding capacity. For each knot configuration, 6 sequential knots were made including the initial sliding knot and additional 5 knots by incrementing one half hitches at a time. Each added half-hitch were in reversing half-hitches with alternate posts (RHAPs) fashion. For each sequential knot configuration, 12 knots were made by No. 2 braided sutures. On the servo-hydraulic material testing system (Instron 8511, MTS, Minneapolis, MN), cyclic loading, load to clinical failure (3-mm displacement), load to ultimate failure, and mode of failure were measured. Results: Most of the initial loop without additional half-hitch showed dynamic failure with cyclic loading. The mean displacement after the end of cyclic loading decreased with each additional half-hitches. SMC and Giant knot reached plateau to 0.1 mm or less displacement after one additional half-hitch, shereas Field and Duncan loop needed 3 additional half-hitches. The SMC and Duncan knots needed 1 additional half-hitch to reach greater than 80N at clinical failure, whefeas the other 2 knots needed2 additional half-hitches. For the load exceeding 100N for clinical failure, the SMC knot required 3 additional half-hitches and the other three knots needed 4 additional half-hitches. As the number of additional half-hitches incremented, the mode of failure switched from pure loop failure (slippage) to material failure (breakage). Duncan loop showed poor loop security in that even with 5 additional half-hitches, some failed by slippage (17%). On the other hand, after 3 additional half-hitches, the 3 other knots showed greater than 75% of failure by material breakage mode (SMC and Field 92%, Giant 75%). Conclusion: Even with its own locking mechanism, lockable sliding knot alone does not withstand the initial dynamic cyclic load. For all tested variables, SMC knot requires a minimum of 2 additional half-hitches. Duncan knot may need more than 3 additional half-hitches for optimal security. All knots showed a mear plateau in knot security with 3 or more additional half-hitches.

• Journal of the Korean GEO-environmental Society
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• v.19 no.4
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• pp.27-32
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• 2018

There were many ground excavation projects from past to present to make effective use of the limited land. And it is very important to predict the ground behavior depending on construction stage for ground excavation. Excavation of the ground involves changes in the stress and displacement of the ground around the excavated surface. Thus it affects the stability of the adjacent structure as well as the excavated surface. Therefore, it is very important to predict the ground behavior and stability of adjacent structure. And nowadays, numerical analysis methods are most often used to predict the effects of ground excavation. Recent, improvements of numerical analysis programs, along with improved computer performance, have helped solve complicated ground problems. However, except some specialized numerical analysis, most numerical analysis often predicts larger excavation floor displacement than field data due to adopt the Mohr-Coulomb analysis model. As a result, it raise the problem that increasing the amount of support on ground and structure. In this study, ground behavior analysis depending on analysis model (Mohr-Coulomb, Duncan-Chang, Modified Mohr-Coulomb and Hardening Soil model) has been carried out through the numerical analysis. When numerical analysis is carried out, this study is expected to be used as a basic data for adopting a suitable analysis model in various ground excavation project.

• Journal of Navigation and Port Research
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• v.31 no.5 s.121
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• pp.377-383
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• 2007

The number of calling ports has been decreased and the degree of inter- and intra-port competition has been increased, which is caused by the market trends that shipping liners have and operate their own terminals, strategic M & A frequency occurs among shipping liners, and container vessel size is increasing. The trends also cause shipping liners to change the evaluation factors for decision to call a particular port such as port preference, potential for growth, port competitiveness, etc. Since the decision of liners greatly influences the policies for port and terminal development, it is worth having interest in the evaluation factors. Therefore, this work intended to evaluate 8 major ports (Port of Singapore, Hong Kong, Shanghai, Busan, Rotterdam, Kaoshing, and Tokyo) with regard to liners' evaluation factors (calling port preference, potential for growth and port competitiveness) and to classify ports by similarity of evaluation factors with the methodologies of ANOVA analysis and Duncan test. The result shows implication for liners' viewpoint to evaluate major ports in the world.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.41-47
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• 2008

The purpose of this study was to provide foundations for proper stretching method not to lose muscle strength caused by shrink of muscle for preventing injury and improving performance when we make training programs. This study compared and analyzed isokinetic variables related to the static stretching frequency of knee joint extensor by isokinetic instruments applied to normal adults. 45 normal adults are randomly sampled into 3 different groups. All the measured variables were processed with SPSS and, means and standard deviations at each angle speed were calculated. The difference of means between before and after stretching of each groups were processed by paired t-test. One-way ANOVA and after test(Duncan) This study was able to see that stretching decrease acute isokinetic muscle strength High frequency stretching group showed more efficient decrease of muscle strength than low frequency stretching group. As a result, making training program for a game requiring strong muscle strength should consider proper stretching method not to lose muscle strength.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.16
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• pp.245-264
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• 2001

This study aims to evaluate and compare the service quality level of major container ports in Asia. Seven factors are used to evaluate the port service qualities; informational assistance, location, processing speed, facilities, port operation, costs, and user convenience. Ten ports are selected as a sample; Singapore, Kobe, Osaka, Kaohsiung, Hong Kong, Shanghai, Tianjin, Busan, Kwangyang and Inchon. ANOVA and Duncan's multiple range test are used to analyze the survey data. The empirical results shows that, in general, Korean ports provides poorer service qualities than Singapore, Hong Kong, Kobe, and Osaka. Furthermore, the service quality levels of Korean ports are similar to or no better than Chinese ports.