• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.10
• /
• pp.1229-1235
• /
• 2011

Fatigue tests were conducted on the aluminum alloy, A7075-T6 to determine the most reliable fretting fatigue damage parameter. Specimens with grooves were used, so that either fretting fatigue crack at the pad/specimen interface or plain fatigue crack at the groove could be nucleated, depending on the pad pressure. Both the crack nucleation location and initial crack orientation were examined using optical microscopy, and the results were used to assess the reliability of the various fretting fatigue damage parameters that have been most commonly used in the literature. Finite element analysis was employed to obtain the stress and strain data of the specimen, which were needed to estimate the parameter values and the orientation of the critical plane. It was revealed that both the Fatemi.Socie and McDiarmid parameters, which assume shear-mode fatigue cracking, are the most reliable.

• Journal of Wetlands Research
• /
• v.18 no.3
• /
• pp.282-285
• /
• 2016

Peregrine falcon (Falco peregrinus) are listed as endangered species and Natural monument #323 in Korea, and this study examined the possibility of extinct of peregrine falcon in Jang Hang wetland near Han river using with the application of Population Viability Analysis (PVA) technique. In Jang Hang wetland areas population was monitored during 1999-2005 averaging 10.8 individuals and PVA analysis was done for the 5 years (2015-2020) using the average population size. Using the initial population was estimated 20% of extinct rate during the time. This estimation was quite low considering water pollution and loss of habitat. Also PVA only used population size lacking in other life history information. Nonetheless falcon population can be in risk of extinction if the current construction of crossovers in the river, cement bank are maintained. Long term information regarding life history needs essential.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.28 no.5
• /
• pp.257-264
• /
• 2016

In this study, experiments for measurements of entrainment rate of fluid mud were carried out using annular flume domestically for the first time. Six entrainment tests using kaolinite sediments were conducted with different initial concentrations of fluid mud. It is shown that sediment settling counteracts the otherwise buoyancy dependent entrainment of fluid mud, and that the settling effect leads to a measurably decreased entrainment rate at higher Richardson numbers in comparison with entrainment of salt water, due to additional dissipation of turbulent kinetic energy in the interfacial layer. Through the comparison with previous other studies, the overall performance of the annular flume, the experimental procedure and the test results in simulating the entrainment of fluid mud are shown to be good enough to verify.

• Health Policy and Management
• /
• v.28 no.3
• /
• pp.315-319
• /
• 2018

This paper aims to make a step-by-step strategy to formulate an unified health system by clarifying and overcoming challenges facing South and North Korea and to estimate costs needed for South Korea to assist North Korea to recover to normal health delivery system. We explored implications through literature review and estimated costs under the assumption that supportive activities be provided for 5 years in three ways: support for the development of health and medical care manpower; support for health and medical facilities; and support for the provision of both preventive and primary health care. Step-by-step strategy is formulated for a unified health system with the cost estimation resulting as follows: in case of basic scenario, a total of 3 trillion and 341 billion won (at present value of the year 2017) is in need for the 5-year period at the initial 'recovery support stage' with 135.9 billion won for the development of health and medical care manpower, approximately 2 trillion won for health and medical facilities, and 1.2 trillion won for the provision of both preventive and primary health care. Step-by-step approach is more realistic and applicable in formulating unified health system. Suggested stages are 'recovery support stage,' 'system homogenization stage,' and 'unified system stage.' Strategies at 'recovery support stage' suggested in this paper need to be pursued and followed by those at 'system homogenization stage' and 'unified system stage.'

• Journal of the Institute of Convergence Signal Processing
• /
• v.11 no.3
• /
• pp.203-208
• /
• 2010

In this paper, we convert underwater acoustic signal made by sonar system into digital image. We propose the algorithm that detects target candidate and emphasizes information of target introducing image processing technique for the digital image. The process detecting underwater target estimates background noise in underwater acoustic signal changing irregularly, recomposes it. and eliminates background from original image. Therefore, it generates initial target group. Also, it generates weighted map through proceeding doppler information, ensures information for target candidate through filtering using weighted map for image eliminated background noise, and decides the target candidate area in the single frame. In this paper, we verified that proposed algorithm almost had eliminated the noise generated irregularly in underwater acoustic signal made by simulation, targets had been displayed more surely in the image of underwater acoustic signal through filtering and process of target detection.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.12
• /
• pp.97-106
• /
• 2011

To analyze the lateral load-deflection behavior of steel-concrete composite drilled shafts, a series of lateral pile load tests were performed. The test results were compared with the results from various analytical methods for lateral pile behaviors using the coefficients of subgrade reaction ($k_h$) estimated by pressuremeter test (PMT) and standard penetration test (SPT). As a result, it was found that the analytical methods using the $k_h$ estimated by SPT N value were not suitable for evaluating the pile head lateral load-deflections of the piles within the allowable deflection. However, the methods using the $k_h$ calculated from PMT were able to represent the initial lateral behavior at the head of the piles fairly well. Also, the method by the pressuremeter curve, which was applied directly to the p-y curve of the piles, offered a reasonable lateral behavior estimation by applying the correction factor to the pile materials.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.20 no.1
• /
• pp.26-33
• /
• 2012

Competition between air transportation and railways has grown fiercer in major countries around the world with the rise of high-speed railways. In South Korea, air passenger travel has been rapidly decreasing since the initial launch of the Seoul-Pusan KTX line in 2004 and second opening that followed in 2010. Further expansion of the high-speed railway is expected. At present, research efforts to verify the validity of constructing an underwater express railway tunnel between Ho-nam and Jeju Island are taking place. Considering the possible high speed railway connection between Seoul and Jeju Island, this thesis has analyzed the choice behavior of existing passengers of the major and low-cost carriers. For this, Stated Preference (SP) research has been performed for three variables, including fare, travel time and the number of runs, to estimate the substitution rate of each of the three variables. Binomial Logit Model has been estimated with the obtained data. The estimation of the model has found that airline passengers of major and low-cost carriers are willing to pay approximately 7,200 KRW and 5,000 KRW, respectively, to reduce travel time by one hour. If the number of runs in one day increases, it has been estimated that the passengers are willing to pay additional fares of about 390 KRW and 30 KRW, respectively. On the other hand, the substitution rate between the number of runs and the travel time was found to be somewhat insignificant. If the construction of the Seoul-Jeju line progresses in the future, this study could be used as preliminary data for determining fares, travel time and the number of runs.

• Journal of Korean Society for Geospatial Information Science
• /
• v.20 no.3
• /
• pp.41-48
• /
• 2012

Using multi-sensor or multi-temporal high resolution satellite images together is essential for efficient applications in remote sensing area. The purpose of this paper is to estimate geometric difference of translations between high-resolution optical and SAR images automatically. The geometric and radiometric pre-processing steps were fulfilled to calculate the similarity between optical and SAR images by using Mutual Information method. The coarsest-level pyramid images of each sensor constructed by gaussian pyramid method were generated to estimate the initial translation difference of the x, y directions for calculation efficiency. The precise geometric difference of translations was able to be estimated by applying this method from coarsest-level pyramid image to original image in order. Yet even when considered only translation between optical and SAR images, the proposed method showed RMSE lower than 5m in all study sites.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.5
• /
• pp.604-610
• /
• 2018

Recently, due to the rapid growth of the leisure industry, demand for small-scale flotation and mooring pontoon platforms has been increasing rapidly. Standard rules for the design and structural safety of such structures have become necessary. This paper provides criteria that can be referenced when designing pontoon platforms, and also introduces structural safety evaluation procedures. In this study, the structural safety and stability of a 15-meter pontoon platform were investigated through structural design and finite element analysis. For platforms of less than 10 meters in length, a simple structural calculation can be used, but for platforms over 10 meters, a detailed structural strength review must be considered to meet safety guidelines defined in existing regulations. The structural strength of the initial design was examined and its structural safety was verified. For future research, it is an evaluative system was developed that can be used to examine the various loading conditions during design.

• Nuclear Engineering and Technology
• /
• v.39 no.6
• /
• pp.747-752
• /
• 2007

The Proton Engineering Frontier Project (PEFP) has designed and developed a proton linear accelerator facility operating at 100 MeV - 20 mA. The radiological effects of such a nuclear facility on the environment are important in terms of radiation safety. This study estimated the production rates of radionuclides in the soil around the accelerator facility using MCNPX. The groundwater migration of the radioisotopes was also calculated using the Concentration Model. Several spallation reactions have occurred due to leaked neutrons, leading to the release of various radionuclides into the soil. The total activity of the induced radionuclides is approximately $2.98{\times}10^{-4}Bq/cm^3$ at the point of saturation. $^{45}Ca$ had the highest production rate with a specific activity of $1.78{\times}10^{-4}Bq/cm^3$ over the course of one year. $^3H$ and $^{22}Na$ are usually considered the most important radioisotopes at nuclear facilities. However, only a small amount of tritium was produced around this facility, as the energy of most neutrons is below the threshold of the predominant reactions for producing tritium: $^{16}O(n,\;X)^3H$ and $^{28}Si(n,X)^3H$ (approximately 20 MeV). The dose level of drinking water from $^{22}Na$ was $1.48{\times}10^{-5}$ pCi/ml/yr, which was less than the annual intake limit in the regulations.