• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.2
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• pp.106-121
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• 2020

In order to make harbor outskirt facilities robust using the reliability-based design, probabilistic models of wave heights at varying stage of shoaling process optimized for Korean sea waves are prerequisite. In this rationale, we numerically simulate the nonlinear shoaling process of random waves over the beach with a sandbar at its foreshore. In doing so, comprehensive numerical models made of spatially filtered Navier-Stokes Eq., LES [Large Eddy Simulation], dynamic Smagorinsky turbulence closure were used. Considering the characteristics of swells observed at the east coast of Korean Peninsula, random waves were simulated using JONSWAP wave spectrum of various peak enhancement coefficients and random phase method. The coefficients of probabilistic models proposed in this study are estimated from the results of frequency analysis of wave crests and its associated trough detected by Wave by Wave Analysis of the time series of numerically simulated free surface displacements based on the threshold crossing method. Numerical results show that Modified Glukhovskiy wave height distribution, the most referred probabilistic models at finite water depth in the literature, over-predicts the occurring probability of relatively large and small wave heights, and under predicts the occurrence rate of waves of moderate heights. On the other hand, probabilistic models developed in this study show vary encouraging agreements. In addition, the discrepancy of the Modified Glukhovskiy distribution from the measured one are most visible over the surf zone, and as a result, the Modified Glukhovskiy distribution should be applied with caution for the reliability-based design of harbor outskirt facilities deployed near the surf-zone.

• Journal of Animal Science and Technology
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• v.50 no.3
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• pp.285-292
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• 2008

Data were taken from the dairy herd improve- ment program from the year 2000, composed of 10,929 first lactation cows consisting of 290,144 test-day records and 37,723 udder type records. The objective of the study was to estimate genetic and phenotypic correlation between fore udder attachment, rear udder height, rear udder width, udder cleft, udder depth, and somatic cell score (SCS) and to calculate heritability of udder depth, front teat length and SCS in Holstein cattle in Korea. The variance component estima- tion using test day model was determined by a derivative-free algorithm-restricted maximum likeli- hood(DF-REML) analysis method. Generally phenotypic correlations were very low between udder traits and lactation SCS which varied from －0.03 to －0.06. Heritability of all type traits and SCS was smaller than 0.12. The results of this study would be applicable to SCS using linear genetic evaluation for future studies.

• 대한방사선치료학회:학술대회논문집
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• 2005.06a
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• pp.19-22
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• 2005

Introduction: Daily Q.A is the important step which must be preceded in a radiation treatment. Specially, radiation output measurement and laser alignment, SSD indicator related to a patient set-up recurrence must be confirmed for a reasonable radiation treatment. Daily Q.A proceeds correctness and a prompt way, and needs an objective measurement basis. Manufacture of the device which can facilitate confirmation of output measurement and appliances check at one time was requested. Methods and Materials: Produced the phantom formal daily check device which can confirm a lot of appliances check (output measurement and laser alignment, field size, SSD indicator) with one time of set up at a time, and measurement observed a linear accelerator (4 machine) for four months and evaluated efficiency. Result: We were able to confirm an laser alignment, field size, SSD indicator check at the same time, and out put measurement was possible with the same set up, so daily Q.A time was reduced, and were able to confirm an objective basis about each item measurement. As a result of having measured for four months, output measurement within ${\pm}\;2\%$, and measured laser alignment, field size, SSD indicator in range within ${\pm}\;1mm$. Conclusion: We can enforce output measurement and appliances check conveniently and time was reduced and was able to raise efficiency of business. We were able to bring n cost reduction by substitution expensive commercialized equipment. Further It is necessary to makes a product as strong and slight materials, and improve convenience of use.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.3-8
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• 2009

The traction system has been mainly used for rehabilitation and correction of patients with spine or gait diseases in orthopedics or at home. Some problems could occur in human body when patients forced their training using the traction system. So it needs to measure a traction force and control the training time. However, most of products on market have no sensor measuring traction force. Thus we designed and made a sensor detecting traction force using strain gauge, amplifier for transition to output signal and experiment devices for performance test. We carried out experiment of a sensor detecting a traction force and measured electric responses of it with respect to traction loads. Maximum error was within about 1% for experiments in static condition and the average error was about 0.7% for experiments in dynamic condition. We concluded that it is possible to use the developed sensor for measurement of traction force since the maximum output variation of a sensor detecting a traction force was about 0.3% in $0^{\circ}C-60^{\circ}C$ temperature condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1786-1795
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• 2011

The trajectory control for omni-directional mobile robot is not easy. Especially, the tracking control which system uncertainty problem is included is much more difficult. This paper develops trajectory controller of 3-wheels omni-directional mobile robot using fuzzy multi-layered algorithm. The fuzzy control method is able to solve the problems of classical adaptive controller and conventional fuzzy adaptive controllers. It explains the architecture of a fuzzy adaptive controller using the robust property of a fuzzy controller. The basic idea of new adaptive control scheme is that an adaptive controller can be constructed with parallel combination of robust controllers. This new adaptive controller uses a fuzzy multi-layered architecture which has several independent fuzzy controllers in parallel, each with different robust stability area. Out of several independent fuzzy controllers, the most suited one is selected by a system identifier which observes variations in the controlled system parameter. This paper proposes a design procedure which can be carried out mathematically and systematically from the model of a controlled system; related mathematical theorems and their proofs are also given. Finally, the good performance of the developed mobile robot is confirmed through live tests of path control task.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1036-1043
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• 2014

The installation of PV system to the power distribution system is being increased as one of solutions for environmental pollution and energy crisis. Because the output efficiency of PV system is getting decreased because of the aging phenomenon and several operation obstacles, the technology development of output prediction and state diagnosis of PV modules are required in order to improve operation performance of PV modules. The conventional methods for output prediction by considering various parameters and standard test condition values of PV modules may have difficult and complex computation procedure and also their prediction values may produce large error. To overcome these problems, this paper proposes an optimal prediction algorithm and state diagnosis algorithm of PV modules by using least square methods of linear regression analysis. In addition, this paper presents a state diagnosis evaluation system of PV modules based on the proposed optimal algorithms of PV modules. From the simulation results of proposed evaluation system, it is confirmed that the proposed algorithms is a practical tool for state diagnosis of PV modules.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.97-107
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• 2014

Finite element modelling and analysis were conducted for the roll-type steel mats which were placed on loose sand and subjected to a standard truck wheel load in this study. The roll-type steel mats mean that the steel mats can be folded as a circle shape for the carrying to fields in cold regions where workability is limited and are developed for a rapid rehabilitation method for roadway across soft ground which is caused by thawing during the summer season in cold regions. The model is composed of link elements to simulate nonlinear behavior of connections between steel mats, thick shell elements to have flexural stiffness of the steel mats, and springs to simulate characteristics of foundation soils. The structural behaviors of the shell, link elements, and springs were verified at each modelling step through experiment and analysis. Beam and shell analysis without the link elements were conducted and compared to results obtained from the model presented in this study. Significant vertical displacement is shown in the shell model with hinge connections. Therefore, the results demonstrate that the analysis model for the roll-type steel mats on loose sand needs further detail parametric studies.

• Korea journal of population studies
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• v.25 no.1
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• pp.33-50
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• 2002

This study examines cross-national patterns of asymmetry of marriage tables with respect to educational level and tries to measure the degree of gender inequality across nations. A Primary assumption of the study is that gender inequality inhibits symmetric marriage between men and women. As men and women differ more in status, the rate of symmetric marriage between them declines thus producing asymmetric marriage with respect to social status. More specifically, the main object of the study is to develop statistical models and index with which to assess the patterns and degree of asymmetric marriage. Additionally, it is intended to assess the appropriateness of several theoretical perspectives for explaining these variations identified by the statistical models. Two most important such perspectives are industrialism and theory of politics and culture. To answer these questions, this study relies on twenty-seven marriage tables with respect to educational level, some from published tables, and some extracted from other sources. The main findings of the study are: (1) compared to less industrialized countries, more industrialized countries have lower degrees of asymmetric marriage(gender inequality) with respect to educational level, and (2) other things being equal, differences in politics and culture seem to have the some impact on marriage pattern; for instance, social democracy and state socialism reduce the degree of asymmetric marriage while the high emphasis on gender-based hierarchy in Asian countries seems to increase it In short, these results suggest a weaker or modified version of industrialists That is, while with economic growth most nations show a decline in the degrees of asymmetric marriage with respect to social status, for some nations the degrees of asymmetric marriage are affected by their specific politics or cultures.

• Land and Housing Review
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• v.4 no.3
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• pp.271-277
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• 2013

The BNWF (Beam on Nonlinear Winkler Foundation) model is one of the simplest idealizations for a pile embedded in soil as it ignores the continuity of the soil. This method is difficult to model the behavior of pile group foundation subjected to lateral loading. The limitation can be overcome with the utilization of the finite element method (FEM) or finite different method (FDM) to represent a pile element embedded in a soil medium. Both the ground and piles are modeled with soild elements. The solid elements, which do not have rotational degree of freedom, is not appropriate for modeling piles. It can be overcome by substantially increasing the number of elements, which can be prohibitive for 3D modeling. This paper used the beam element and rigid link incorporated in the OpenSees to model the pile. The accuracy of the model is validated through comparison with lateral load test and BNWF analysis. It is shown that the method can capture the measured behavior accurately. It is therefore recommended to be used in group pile analyses.

• Journal of Korean Society of Transportation
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• v.20 no.7
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• pp.95-105
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• 2002

Under a specific roadway alignment condition by design-speed standards, safety of the roadway is determined by an actual operating speed of a driver. This research takes first lanes of four-lane(hi-direction) rural highways as target facility. It also takes the straight and curved lanes of the selected highways for in-depth study. This study used NC-97 to detect speeds of passenger cars whose speeds are not affected by front vehicles. This research analyzed properties of 85th percentile operating speed at upstream of horizontal and through curves under various alignment conditions. The results show that 53∼65 Percent of drivers drive faster than the posted speed-limit (80KPH) by 14∼20 KPH on average. It also shows that the 85th-percentile operating speeds are the lowest at the middle point of curve length when curve radius is smaller. However, they are lowest at 1/4 point of curve length when curve radius is greater. Along roadways where curve radius is small, difference between upstream speed and the speed along the curve is considerably large. On the other hand. the speed difference is setting smaller as the curve radius is increasing. According to the results, significant variables affecting the 85th percentile operating speeds are curve radius and the 85th-Percentile operating speeds of upstream curves.