• The Journal of Engineering Geology
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• v.21 no.1
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• pp.1-13
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• 2011

Joint roughness is one of the most important parameters in analysis of rock slope stability. Especially in probabilistic analysis, the random properties of joint roughness influence the probability of slope failure. Therefore, a large dataset on joint roughness is required for the probabilistic analysis but the traditional direct measurement of roughness in the field has some limitations. Terrestrial LiDAR has advantagess over traditional direct measurement in terms of cost and time. JRC (Joint Roughness Coefficient) was calculated from statistical parameters which are known from quantitative methods of converting the roughness of the material surface into JRC. The mean, standard deviation and distribution function of JRC were obtained, and we found that LiDAR is useful in obtaining large dataset for random variables.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.1-9
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• 2010

We reported the methodology for the shear test which is one of the evaluation procedure for mechanical reliability of flip-chip package. The shear speed and the tip height are found to be two significant experimental parameters in the shear test. We investigated how these two parameters have an influence on the results, the shear strength and failure mode. In order to prove these experimental inconsistency, simulation using finite element analysis was also conducted to calculate the shear strength and to figure out the distribution of plastic energy inside of the solder ball. The shear strength decreased while the tip height increased or the shear speed decreased. A variation in shear strength due to inconsistent shear conditions made confusion on analyzing experimental results. As a result, it was strongly needed to standardize the shear test method.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.45-55
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• 2004

In the past it has been often observed that the shear stresses at failure are much smaller than the shear strength obtained from traditional laboratory tests and conventional analysis technique is inadequate in stiff soil, such as cemented sand. Many researchers have brought attention to the fact that the presence of flaws i.e. fissures, cracks, joints have a great effect on the strength and overall stress-strain behavior of such materials. They have thought that fracture mechanics may appropriately be adopted as a good tool for analysis of these materials. However, the use of fracture mechanics concept especially for cemented sands is faced with difficulties in obtaining relevant parameters, because fracture parameters and predictions are highly dependent on the material constituents and the size of specimens as well as the size of particles. This paper addresses the effects of sizes which include specimen and aggregate on fracture properties of cemented sand. The results of laboratory tests show that the sizes of specimens and particle have a great effect on the fracture properties such as nominal strength of cemented sand.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.4
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• pp.325-330
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• 2018

This paper, following the shape parameters of the minimax distribution, describes the special form of the beta distribution, the Minimax distribution, as a function of the shape parameters for the software reliability model based on the non-homogeneous Poisson process. Characteristics and usefulness were discussed. As a result, the case of the shape parameter 1 of Minimax distribution than less than and greate in mean squared error is the smallest, in determination coefficient, appears to be high, the shape parameter 1 of Minimax distribution regard as an efficient model. The estimated determination coefficient of the proposed model is estimated to be more than 95%, which is a useful model in the field of software reliability. Through this study, software design and users can identify the software failure characteristics using mean square error, decision coefficient, and confidence interval can be used as a basic guideline.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.905-910
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• 2014

The steel grating discussed in this study is a drain cover that enhances the rigidity of the steel frame using an inclined inflow tract for wastewater, facilitates smooth drainage, and prevents the escape of bad smell from the drain. Recently, the urban problem of bad smell in sewerage lines has been hindering the improvement of living standards. Moreover, the frequent failure of existing products deters bad smell prevention measures and results in administrative power and budget wastage. The pressure to reduce budgets propels the increased demand for functional steel grating. Thus, this study focused on optimizing the design parameters of a steel grating by simultaneously considering its rigidity and drainage efficiency.

• Nutrition Research and Practice
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• v.8 no.1
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• pp.94-102
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• 2014

Diet attrition and failure of long term treatment are very frequent in obese patients. This study aimed to identify pre-treatment variables determining dropout and to customise the characteristics of those most likely to abandon the program before treatment, thus making it possible to modify the therapy to increase compliance. A total of 146 outpatients were consecutively enrolled; 73 patients followed a prescriptive diet while 73 followed a novel brief group Cognitive Behavioural Treatment (CBT) in addition to prescriptive diet. The two interventions lasted for six months. Anthropometric, demographic, psychological parameters and feeding behaviour were assessed, the last two with the Italian instrument VCAO Ansisa; than, a semi-structured interview was performed on motivation to lose weight. To identify the baseline dropout risk factors among these parameters, univariate and multivariate logistic models were used. Comparison of the results in the two different treatments showed a higher attrition rate in CBT group, despite no statistically significant difference between the two treatment arms (P = 0.127). Dropout patients did not differ significantly from those who did not dropout with regards to sex, age, Body Mass Index (BMI), history of cycling, education, work and marriage. Regardless of weight loss, the most important factor that determines the dropout appears to be a high level of stress revealed by General Health Questionnaire-28 items (GHQ-28) score within VCAO test. The identification of hindering factors during the assessment is fundamental to reduce the dropout risk. For subjects at risk, it would be useful to dedicate a stress management program before beginning a dietary restriction.

• Journal of Korean Neurosurgical Society
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• v.59 no.4
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• pp.346-351
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• 2016

Objective : Early progressive infarction (EPI) is frequently observed and related to poor functional outcome in patients with middle cerebral artery (MCA) infarction caused by MCA occlusion. We evaluated the perfusion parameters of magnetic resonance imaging (MRI) as a predictor of EPI. Methods : We retrospectively analyzed patients with acute MCA territory infarction caused by MCA occlusion. EPI was defined as a National Institutes of Health Stroke Scale increment ${\geq}2$ points during 24 hours despite receiving standard treatment. Regional parameter ratios, such as cerebral blood flow and volume (rCBV) ratio (ipsilateral value/contralateral value) on perfusion MRI were analyzed to investigate the association with EPI. Results : Sixty-four patients were enrolled in total. EPI was present in 18 (28%) subjects and all EPI occurred within 3 days after hospitalization. Diabetes mellitus, rCBV ratio and regional time to peak (rTTP) ratio showed statically significant differences in both groups. Multi-variate analysis indicated that history of diabetes mellitus [odds ratio (OR), 6.13; 95% confidence interval (CI), 1.55-24.24] and a low rCBV ratio (rCBV, <0.85; OR, 6.57; 95% CI, 1.4-30.27) was significantly correlated with EPI. Conclusion : The incidence of EPI is considerable in patients with acute MCA territory infarction caused by MCA occlusion. We suggest that rCBV ratio is a useful neuro-imaging parameter to predict EPI.

• Journal of Pharmaceutical Investigation
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• v.36 no.4
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• pp.277-282
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• 2006

Lisinopril is one of the angiotensin-converting enzyme inhibitors, which have been used for treatment of hypertension and heart failure. The aim of this study was to evaluate the bioequivalence of two lisinopril tablet, $Lisihexal^{\circledR}$ and $Zestril^{\circledR}$ as a test and reference, respectively. The study was came out on 28 healthy male Korean volunteers in $2{\times}2$ crossover design. An analytical method with LC-MS-MS was developed for the quantification of lisinopril and enalapril(IS) using SPE method. The condition was selective, sensitive and precise in human plasma, that was enough for the pharmacokinetic study of lisinopril. The pharmacokinetic parameters such as $AUC_t,\;AUC_{inf},\;C_{max},\;T_{max}\;and\;t_{1/2}$ were calculated and ANOVA test was used for the statistical analysis of the parameters using log transformed $AUC_t,\;AUC_{inf}\;and\;C_{max}$. $t_{1/2}$ of test and reference drugs were calculated $11.4{\pm}5.1\;and\;16.1{\pm}9.9\;hr$, respectively. The 90% confidence intervals of $AUC_t,\;AUC_{inf}\;and\;C_{max}$ were log 0.9245$\sim$log 1.0603, log 0.9270$\sim$log 1.0601 and log 0.9548$\sim$log 1.1009, within the acceptable range of log 0.8 to log 1.25 by KFDA bioequivalence criteria. Two medications of lisinopril were evaluated bioequivalent and thus may be prescribed interchangeably.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.47-53
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• 2014

The paper investigates the limit state of deflection for short and medium span steel girder bridges. Deflection depends on stiffness of steel girders and integrity of the reinforced concrete slab (composite action). Load and resistance parameters are treated as random variables. A probabilistic model is developed for prediction of the deflection. The structural performance can be affected by deterioration of components, in particular corrosion of steel girders. In addition, the creep of concrete can greatly influence the deflection of composite structures. Therefore, the statistical models for creep and corrosion of structural steel are incorporated in the model. Structures designed according to the AASHTO LRFD Code are considered. Load and resistance models are developed to account for time-variability of the parameters. Monte Carlo simulations are used to estimate the deflections and probabilities of serviceability failure. Different span lengths and girder spacing are considered for structures designed as moment-controlled and deflection-controlled. A summary of obtained results is presented.

• Coupled systems mechanics
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• v.7 no.2
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• pp.197-209
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• 2018

Fiber-reinforced concrete (FRC) is a material with increasing application in civil engineering. Here it is assumed that the material consists of a great number of rather small fibers embedded into the concrete matrix. It would be advantageous to predict the mechanical properties of FRC using nondestructive testing; unfortunately, many testing methods for concrete are not applicable to FRC. In addition, design methods for FRC are either inaccurate or complicated. In three-point bending tests of FRC prisms, it has been observed that fiber reinforcement does not break but simply pulls out during specimen failure. Following that observation, this work is based on an assumption that the main components of a simple and rather accurate FRC model are mechanical properties of the concrete matrix and fiber pullout force. Properties of the concrete matrix could be determined from measurements on samples taken during concrete production, and fiber pullout force could be measured on samples with individual fibers embedded into concrete. However, there is no clear relationship between measurements on individual samples of concrete matrix with a single fiber and properties of the produced FRC. This work presents an inverse model for FRC that establishes a relation between parameters measured on individual material samples and properties of a structure made of the composite material. However, a deterministic relationship is clearly not possible since only a single beam specimen of 60 cm could easily contain over 100000 fibers. Our inverse model assumes that the probability density function of individual fiber properties is known, and that the global sample load-displacement curve is obtained from the experiment. Thus, each fiber is stochastically characterized and accordingly parameterized. A relationship between fiber parameters and global load-displacement response, the so-called forward model, is established. From the forward model, based on Levenberg-Marquardt procedure, the inverse model is formulated and successfully applied.