• Journal of Korea Port Economic Association
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• v.37 no.4
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• pp.127-144
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• 2021

The purpose of this study is to derive service factors based on the "Rail Statistical Yearbook" data of railroad service providers from 1990 to 2019, and to analyze the effect of the service factors on the operating profit ratio(OPR), a representative management performance variable of railroad transport service providers. In particular, it has academic significance in terms of empirical research to evaluate whether the management innovation of the KoRail has changed in line with the purpose of establishing the corporation by dividing the research period into the first period (1990-2003) and the latter (2004-2019). The contents of this study investigated previous studies on the quality of railway passenger transportation service and analyzed the contents of government presentation data related to the management performance evaluation of the KoRail. As an empirical analysis model, a research model was constructed using OPR as a dependent variable and service factor variables of infrastructure, economy, safety, connectivity, and business diversity as explanatory variables based on the operation and management activity information during the analysis period 30 years. On the results of research analysis, OPR is that the infrastructure factor is improved by structural reform or efficiency improvement. And economic factors are the fact that operating profit ratio improves by reducing costs. The safety factor did not reveal the significant explanatory power of the regression coefficient, but the sign of influence was the same as the prediction. Connectivity factor reveals a influence on differences between first period and latter, but OPR impact direction is changed from negative in before to positive in late. This is an evironment in which connectivity is actually realized in later period. On diversity factor, there is no effect of investment share in subsidiaries and government subsidies on OPR.

• Analytical Science and Technology
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• v.35 no.6
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• pp.267-273
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• 2022

In this study, a quality evaluation was conducted to change the sell-by date of fish cakes to the use-by date. For product quality evaluation, storage conditions were set at 5, 10, and 15 ℃, and five tests of pH, acid value, volatile basic nitrogen, bacterial count, and coliform group were performed. As a result of the experiment, the quality safety limit period of fish cakes stored at 5 ℃ was 43 days, that of fish cakes stored at 10 ℃ were 30 days, and that of fish cakes stored at 15 ℃ was 7 days. Among the five test items used for quality evaluation, the quality-limit indicators were acid value, number of bacteria, and coliform groups. The index that determined the quality safety-limit period under the three storage conditions was the bacterial count. The sell-by date of the fish cake used in this experiment was 10 days. However, through quality evaluation, the use-by date at 10 ℃ was 28.5 days, which was calculated by multiplying the 30 days; the quality limit period, by a safety factor of 0.95. However, this study conducted a quality study on one item of fish cakes from a single company, and it was difficult to use the quality safety-limit period and use-by date set in this study universally. To change the sell-by date to the use-by date, extensive quality research on various products will be required. If this system is well established, it can help reduce food waste through proper consumption of food, and consumers will be able to consume food with confidence.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1178-1185
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• 2010

Recently, high speed of container freight cars is causing fatigue damage of wheel. Sudden failure accidents cause a lot of physical and human damages. Therefore, damage analysis for wheel prevents failure accident of container freight car. Wheel receives mechanical and thermal loads at the same time while rolling stocks are run. The mechanical loads applied to wheel are classified by the horizontal load from contact of wheel and rail in curve line section and by the vertical force from rolling stocks weight. Also, braking and deceleration of rolling stocks cause repeated thermal load by wheel tread braking. Specially, braking of rolling stocks is frictional braking method that brake shoe is contacted in wheel tread by high breaking pressure. Frictional heat energy occurs on the contact surface between wheel tread and brake shoe. This braking converts kinetic energy of rolling stocks into heat energy by friction. This raises temperature rapidly and generates thermal loads in wheel and brake shoe. There mechanical and thermal loads generate crack and residual stress in wheel. Wetenkamp estimated temperature distribution of brake shoe experimentally. Donzella proposed fatigue life using thermal stress and residual stress. However, the load applied to wheel in aforementioned most researches considered thermal load and mechanical vertical load. Exact horizontal load is not considered as the load applied to wheel. Therefore, above-mentioned loading methods could not be applied to estimate actual stress applied to wheel. Therefore, this study proposed safety estimation on wheel of freight car using heat-structural coupled analysis on the basis of loading condition and stress intensity factor.

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.11-24
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• 2013

This study presents a design method for typical rainfall-induced landslide considering in-situ matric suction. Actual landslide data are used to validate the proposed method. The soil-water characteristic curve (SWCC) and unsaturated permeability are experimentally determined to estimate hydraulic properties of testing site. The field measurement of matric suction is carried out to monitor in-situ matric suction in a natural slope subjected to rainfall infiltration, which is incorporated in the landslide analysis. The wetting band depth and safety factor of the slope are assessed to clarify the effect of domestic rainfall pattern. Especially, the effect of antecedent rainfall on the slope stability is investigated and discussed in terms of wetting band depth using parametric study. It is found from the result of this study that proposed design method can consider the characteristic of unsaturated soil and effect of antecedent rainfall. The location of the scarp zone is fairly well predicted by proposed design method. Moreover, heavy rainfall, concentrated in the backward part with time, causes the lowest safety factor of the slope. These results demonstrate that decrease in matric suction due to antecedent rainfall may trigger slope instability. After the antecedent rainfall, additional rainfall may cause the slope failure due to increasing wetting band depth.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.161-169
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• 2012

This paper presents the safety and strength of simplified composite H-beam panel bridges (SCHPBs) using 3-dimentional finite-element program, ABAQUS (2007) and experimental tests. Two finite-element models (one-steel-girder-and-composite-deck model and four-steel-girder-and-wide-composite-deck model) were reviewed to predict the strength and load distribution factor (LDF) values of the composite bridges. Based on the results of the finite-element analyses, the behaviors of the two models were investigated, and deflection and strain gauges for the experimental specimens were set up to obtain the ultimate strengths and the LDF values. The ultimate strength of the one-steel-girder-and-composite-deck specimen was estimated to be 840 kN. The yield and plastic moments of the four-steel-girder-and-wide-composite-deck specimen were obtained to be 2.4 and 4.1 times the design moment based on the live loading condition of the Korea Bridge Design Specifications (2005). The SCHPB were found to have enough strength for safety under and after construction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.504-509
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• 2012

Automotive suspension mat is installed at seat back frame. As the back part of passenger is aupported by suspension mat, it is prevented from the pressure concentration. The tired feeling at driving is minimized and the comfortable feeling is increased. In this study, vibration and fatigue are analyzed with plastic suspension mat modelled by 3 Dimension. By the analysis result, the natural frequency becomes 30 Hz with life of $10^6$ cycle and safety factor of 1.6055. Development time and evaluation cost can be cut down by utilizing this analytical technique.

• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.27-34
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• 1988

Since the lack of the spent fuel storage capcity has been expected for all Korean nuclear power plants in the mid-1990s, the maximum density rack (MDR) with consolidated fuels can be proposed to overcome the shortage of the storage capacity in KNU 9 & 10 which have most limited capacities. To ensure the safety when the alternatives are applied in the KNU 9 & 10, the multiplication factor are calculated with varying the rack pitch and the thickness of consolidated storage box by the AMPX-KENO IV codes. The computing system is verified by the benchmark calculation with criticality experiments for arrays of consolidated fuel modules, which was reported by B & W in 1981. Also an abnormal condition, i.e. malposition accident, is simulated. The results indicate that the KNU 9 & 10 storage pools with consolidated fuel are safe in the view of the criticality. Thus the storage capacity can be expanded from 9/3 cores into 27/3 cores even with considering equipments and cooling spaces.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.18-25
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• 2006

In order to perform system requirements quickly and accurately, an automatic design program of solid rocket motors(SRM) structure designated as the 'ProDes software' has been developed and verified. from given system design criteria and constraints, it has the capabilities to design, analysis, simulation and drawing process to greatly reduce the over 'design cycle time' and manpower of a project. The conception of the program is modular, and calculations are performed step by step allowing parametric design studies and providing final selected design goal. Each configurations of SRM components and joint types composed of various master models is obtained from the data base module of the library. Between the design results of the ProDes software and those of the previous detail design of the established motor showed good agreements.

• Geotechnical Engineering
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• v.5 no.1
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• pp.27-34
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• 1989

This study presents a probabilistic analysis of the stability of homogeneous soil slopes during earthquakes. The stability of the slope is measured through its probability of failure rather than the customary factor of safety. The maximum horizontal ground acceleration is deterimined with Donovan and McGuire equation. The earthquake magnitude (m) is a random variable the Probability density function f(m) has been obtained with a use of Richter law. The potential failure surfaces are taken to be of an exponential shape (log-spiral) , Uncertainties of the shear strength parameters along potential failure surface are expressed by one-dimensional random field model. From a first order analysis the mean and variance of safety margin is osculated. The dependence on significant seismic parameters of the probability of failure of the slope is examined and the results are presented in a number of graphs and tables. On the base of the results obtained in this study, it is concluled that (1) the present model is useful in assessing the reliability of soil slopes under both static and seismic conditions: and (2) the probability of failure of a soil slope is greatly affected by the values of the seismic parameters that are associated with it.

• Journal of the Korean Society of Radiology
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• v.17 no.2
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• pp.249-255
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• 2023

In this study, radiation exposure doses were measured in the course of clinical practice of radiation workers, radiological technologists in the radiation-related worker group, and preliminary-radiological technologists who were classified as frequent visitors. Radiological technologists who worked in the radiation area of C University Hospital in Incheon for a year from January 2021 and 121 students who completed clinical practice at the same medical institution from July 1 to August 31 were the subjects of the study. The nominal risk factor based on ICRP 103 was used to evaluate the probability of side effects due to the exposure dose to the lungs, which are organs at risk of damage due to radiation exposure dose. During the clinical practice period, radiology students, who were classified as frequent visitors, had a surface dose of 0.98 ± 0.14 mSv and a deep dose of 0.93 ± 0.14 mSv. In other words, 6.7 per 1,000,000 for shallow dose and 6.4 per 1,000,000 for deep dose were found to have side effects due to exposure to the lungs. This is a value in terms of exposure dose in one year. Considering that the radiation (science) education course is 3 or 4 years, systematic management and attention to prospective radiation workers who are going to clinical practice are required, and the stochastic effect of radiation In relation to this, it is considered that it will be used as basic data for radiation safety management.