• Journal of Korean Ophthalmic Optics Society
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• v.17 no.3
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• pp.273-278
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• 2012

Purpose: Average of the maximum accommodation amplitude of myopia in different generation, early 20's and early 40's were compared according to gender, degree of myopia. Methods: Maximum amplitude of accommodation for each 100 patients of early 20's and 40's were measured with push-up method. Maximum amplitude of accommodation expectations based on Hofstetter formula were classified into three groups of under, normal and excess. Results: The average of amplitude of accommodation was 9.77~11.64 D $(10.77{\pm}2.49D)$ in early 20's and 4.67~6.21 D $(5.34{\pm}1.28D)$ in early 40's. In early 20's, minimum expectations of amplitude of accommodation for under, normal and excess groups were 20%, 75%, and 5%, repectively. In early 40's, excess and under groups were 5% and 18%, repectively, but there was no excess group. Conclusions: According to increasing age, amplitude of accommodation of both age groups showed decreased, and no significant difference was found in degree of myopia with gender. Difference between mean of expected accommodation amplitude and maximum of accommodation amplitude was compared, and it was found that maximum of accommodation amplitude of 20's was smaller than mean of expected accommodation. From the result, it was expected that people in early 20's who have more working times might have festinated accommodative insufficiency than 40's.

• Journal of Radiation Protection and Research
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• v.38 no.1
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• pp.22-28
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• 2013

The skyshine effect is an essential and important phenomenon in the shielding design of the high energy accelerator. In this study, a new estimation method of neutron skyshine was proposed and was verified by comparison with existing methods. The effective dose of secondary neutrons and photons at the locations that was far away from high-energy electron accelerator was calculated using FLUKA and PHITS Monte Carlo code. The transport paths of secondary radiations to reach a long distance were classified as skyshine, direct, groundshine and multiple-shine. The contribution of each classified component to the total effective dose was evaluated. The neutrons produced from the thick copper target irradiated by 10 GeV electron beam was applied as a source term of this transport. In order to evaluate a groundshine effect, the composition of soil on the PAL-XFEL site was considered. At a relatively short distance less than 50 m from the accelerator tunnel, the direct and groundshine components mostly contributed to the total effective dose. The skyshine component was important at a long distance. The evaluated dose of neutron skyshine agreed better with the results using Rindi's formula, which was based on the experimental results at high energy electron accelerator. That also agreed with the estimated dose using the simple evaluation code, SHINE3, within about 20%. The total effective dose, including all components, was 10 times larger than the estimated doses using other methods for this comparison. The influence of multiple-shine path in this evaluation of the estimation method was investigated to be bigger than one of pure skyshine path.

• Journal of the Korean GEO-environmental Society
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• v.13 no.4
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• pp.13-26
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• 2012

The deformation modulus of rock masses is a very important design factor for the computation of stability of tunnels and their support systems. Several empirical formulas to estimate the deformation modulus using simple rock classification methods such as RQD or RMR are widely used because field tests to evaluate the deformation modulus are very expensive and time consuming work. However, these formulas can be depended on experiences from the characteristics of local sites in each country. So it is possible that there might be limitations to estimate appropriate deformation modulus in South Korea using the empirical formulas. Therefore, in this study, the applicability of empirical formulas was analyzed by comparing estimated value with the measured value from eight sites in South Korea. The results show that the estimated value based on the empirical formulas partially have tendency to overestimate. Especially, in case of sedimentary rocks, it was too difficult to apply to the empirical formulas because there was no relation ship between estimated value and measured value. For these reasons, additional data from many tests and accurate analyses are necessary to evaluate the estimation method for the deformation modulus considering the local characteristics of rock masses.

• Journal of the Korean GEO-environmental Society
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• v.20 no.3
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• pp.21-30
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• 2019

Composite pile, which is composed of the steel pipe pile in which the large horizontal force acts and the PHC pile in which the small horizontal force acts by a special connecting devices, is being commercialized as a base material for civil engineering structures. The core of such a composite pile can be said to be a design criterion for estimating the joint position and stability of the connection device between steel pipe pile and PHC pile. In Korea, there is no precise specification for the location of composite pile joints. In the LH Design Department (Korea Land & Housing Corporation, 2009), "Application of composite pile design and review of design book marking" was made with reference to Road Design Practice Volume 3 (Korea Expressway Corporation, 2001). this is used as a basis of the design of the composite pile. It can not be regarded as a section change of the composite pile, so it has a limitation in application. Therefore, In this study, we propose a design criterion for the location of the section of the composite pile (joint of steel pipe pile and PHC pile) and evaluate the stability and economical efficiency of it by using experimental method and analytical method. Analysis of composite pile design data installed in 79 domestic bridges abutment showed that the stresses, bending moments, and displacements acting on the pile body and connection of the pile were analyzed. Through the redesign process, it was confirmed that the stresses generated in the connecting device occur within the allowable stress values of the connecting device and the PHC pile. In conclusion, the design proposal of composite pile joint location through empirical case study in this study is an improved design method considering both stability and economical efficiency in designing composite pile.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.519-530
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• 2023

Moye's analytical solution was examined as a method for constant-head tests under steady-state conditions, and results were compared with transient-state analyses in in situ hydraulic tests. The sensitivity of hydraulic conductivities calculated using Moye's method increased with the length of the test section, which should be as large as possible under test conditions. Particularly in low-permeability media with less than 10^-8 m/sec of hydraulic conductivity, hydraulic conductivity is lower than that under transient-state conditions and can be recalculated by adjusting the boundary between radial and spherical flow assumed in Moye's equation. Constant-head tests performed in the research borehole at the KAERI Underground Research Tunnel (KURT) indicated that transmissivities derived from the constant-head withdrawal test under transient-state conditions in low-permeability media were higher than those derived from steady-state tests, likely because the groundwater flow boundary was smaller than the "half of the test-section length"assumed by Moye's equation. When interpreting constant-head test results for crystalline rock, the hydrogeological properties of the medium may be better understood by considering assumed conditions accompanying analysis of the steady-state condition and comparing them with results for the transient-state analysis, rather than simply assuming properties based on steady-state analyses.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.179-193
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• 1994

In the development of engineering designs, decisions are required irrespective of the state of completeness and quality of information, and are formulated under conditions of uncertainty. Furthermore, under conditions of uncertainty the design invokes risks. Thus, in the design of the structures, the currently used deterministic design method does not provide a realistic assessment of the actual safety or the reliability of the structures. It is desirable that decisions required in The process of the design invariably must be made based on the reliability analysis. Properties of soil material are subject to more uncertainty than those of other structural material. In the field of soil mechanics and foundation engineering, it needed to develop reliability-based design methods. In order to simplify the reliability analysis or the reliability-based design process of the structures associated with the active earth pressure, it is necessary to find the variation and the distribution type of the active earth pressure calculated from the basic properties of soils. Monte Carlo simulation is performed to obtain the relationship between the variation of the active earth pressure for cohessionless soils calculated by using Rankine formula and the basic soil properties and the distribution type of the earth pressure. A series of regression equations obtained by utilizing the multi-linear regression analysis is suggested in this paper and the sensitivity of the basic soil properties to the variation of The earth pressure is investigated. The type of distribution of the active earth pressure was found to be the beta distribution in most cases or to be very similar to the beta distribution, if the basic soil variables are normally distributed.

• Journal of the Korean Professional Engineers Association
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• v.20 no.3
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• pp.15-25
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• 1987

Statistical control charts are useful tools to monitor and control the manufacturing processes and are widely used in most Korean industries. Many Korean companies, however, do not always obtain desired results from the traditional control charts by Shewhart such as the X-chart, X-chart, X-chart, etc. This is partly because the quality charterstics of the process are not distributed normally but are skewed due to the intermittent production, small lot size, etc. In Shewhart X-chart, which is the most widely used one in Korea, such skewed distributions make the plots to be inclined below or above the central line or outside the control limits although no assignable causes can be found. To overcome such shortcomings in nonnormally distributed processes, a distribution-free type of confidence interval can be used, which should be based on order statistics. This thesis is concerned with the design of control chart based on a sample median which is easy to use in practical situation and therefore properties for nonnormal distributions may be easily analyzed. Control limits and central lines are given for tile more famous nonnormal distributions, such as Gamma, Beta, Lognormal, Weibull, Pareto, Truncated-normal distributions. Robustness of the proposed median control chart is compared with that of the X-chart, the former tends to be superior to the latter as the probability distribution of the process becomes more skewed. The average run length to detect the assignable cause is also compared when the process has a Normal or a Gamma distribution for which the properties of X are easy to verify, the proposed chart is slightly worse than the X-chart for the normally distributed product but much better for Gamma-distributed products. Average Run Lengths of the other distributions are also computed. To use the proposed control chart, the probability distribution of the process should be known or estimated. If it is not possible, the results of comparison of the robustness force us to use the proposed median control chart based on a normal distribution. To estimate the distribution of the process, Sturge's formula is used to graph the histogram and the method of probability plotting, $X^2$-goodness of fit test and Kolmogorov-Smirnov test, are discussed with real case examples. A comparison of the propose4 median chart and the X chart was also performed with these examples and the median chart turned out to be superior to the X-chart.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.10 no.16
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• pp.101-106
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• 1987

Statistical control charts are useful tools to monitor and control the manufacturing processes and are widely used in most Korean industries. Many Korean companies, however, do not always obtain desired results from the traditional control charts by Shewhart such as the $\bar{X}$-chart, $\bar{X}$-chart, $\bar{X}$-chart, etc. This is partly because the quality charterstics of the process are not distributed normally but are skewed due to the intermittent production, small lot size, etc. In Shewhart $\bar{X}$-chart. which is the most widely used one in Kora, such skewed distributions make the plots to be inclined below or above the central line or outside the control limits although no assignable causes can be found. To overcome such shortcomings in nonnormally distributed processes, a distribution-free type of confidence interval can be used, which should be based on order statistics. This thesis is concerned with the design of control chart based on a sample median which is easy to use in practical situation and therefore properties for nonnormal distributions may be easily analyzed. Control limits and central lines are given for the more famous nonnormal distributions, such as Gamma, Beta, Lognormal, Weibull, Pareto, Truncated-normal distributions. Robustness of the proposed median control chart is compared with that of the $\bar{X}$-chart; the former tends to be superior to the latter as the probability distribution of the process becomes more skewed. The average run length to detect the assignable cause is also compared when the process has a Normal or a Gamma distribution for which the properties of X are easy to verify, the proposed chart is slightly worse than the $\bar{X}$-chart for the normally distributed product but much better for Gamma-distributed products. Average Run Lengths of the other distributions are also computed. To use the proposed control chart, the probability distribution of the process should be known or estimated. If it is not possible, the results of comparison of the robustness force us to use the proposed median control chart based oh a normal distribution. To estimate the distribution of the process, Sturge's formula is used to graph the histogram and the method of probability plotting, $\chi$$^2$-goodness of fit test and Kolmogorov-Smirnov test, are discussed with real case examples. A comparison of the proposed median chart and the $\bar{X}$ chart was also performed with these examples and the median chart turned out to be superior to the $\bar{X}$-chart.

• Journal of the Korean Society for Library and Information Science
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• v.8
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• pp.183-207
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• 1981

Library standards have been the source of considerable controversy, whereas many problems are involved in developing stardard for university library collections. For evaluation purposes, standards should be precise, quantifiable and measurable. In the United States, however, standards for academic libraries are limited to qualitative statements and principles. Quantitative standards, when given, are ususally related to the number of population in the institution being served, or the prescribed quantitative objectives are often arbitrarily formulated by value judgements. The study in this paper attempts to explain the problems involved in developing quantitative standard for academic library collections. Two problems facing in the formulation of the optimal size of collection are identified. One is the theoretically faulty concept of adequacy of collection to meet the situations of diversity of university libraies, and the other is the difficulties in quantification and measurement, along with the lack of concept of adequacy of collection. However, quantification of adequate size of collection is proved to be useful on the pratical level, even though not valid theoretically. ACRL, Clapp/Jordan and Voigt developed formulas or models for setting the optimal size of a library collection for any particular university library. The main purpose of this study is the analysis of the above formulas. ACRL standard was drawn from obervation and analysis of statistcs in leading library collections. In academic field, this judgement appears to have been based on the assumption that a high-grade institution would be apt to have a good library collection. This study criticizes ACRL standard for its failure to include some determinants of measurements, and points out the limitations of the standard. In contrast. Clapp/Jordan developed a formula rather scientifically based upon bibliographical sources. This is similarly empirical but has the advantage of bringing into play the elements which make universities diverse in nature. Both ACRL and Clapp/Jordan formulas share two major defects. (1) the specific subject needs of the collection are not indiacted directly, and (2) percentage rate of growth is an indicator in measuring the potential utility of a collection. Thus both formulas failed to provide a basis for meaningful evaluation. Voigt further developed a model for determining acquisition rates for currently published materials based on bibliographic technique. Voigt model encourages experimentation with different programs and different allocations of input resources, designed to meet the needs of the library's particular population. Standard for university library collections can be formulated in terms of input(traditional indicator), or additionally, in terms of output(cost-effectiveness). Cost effectiveness is expressed as user satisfaction, ability to provide wanted materials within a reasonable time period. Thus simple quantitative method does not cover all the situations of diversity of university library collections, nor measures the effectiveness of collections. Valid standard could not be established without further research.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.2
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• pp.1-8
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• 2024

The expansion joint is installed to offset the expansion of the superstructure and must ensure sufficient gap during its service life. In detailed guideline of safety inspection and precise safety diagnosis for bridge, damage due to lack or excessive gap is specified, but there are insufficient standards for determining the abnormal behavior of superstructures. In this study, a data-based maintenance was proposed by continuously monitoring the expansion-gap data of the same expansion joint. A total of 2,756 data were collected from 689 expansion joint, taking into account the effects of season. We have developed a method to evaluate changes in the expansion joint-gap that can analyze the thermal movement through four or more data at the same location, and classified the factors that affect the superstructure behavior and analyze the influence of each factor through deep learning and explainable artificial intelligence(AI). Abnormal behavior of the superstructure was classified into narrowing and functional failure through the expansion joint-gap evaluation graph. The influence factor analysis using deep learning and explainable AI is considered to be reliable because the results can be explained by the existing expansion gap calculation formula and bridge design.