• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.67-72
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• 2010

In this study, performance analysis and design optimization is carried out for a multi-rate spring brake system, which is used in a cable ride to stop the arriving passengers in safe and comfortable manner. Mathematical model for the spring is developed toward the objective of minimizing the impact at the arrival while satisfying the constraint of limited distance at the stop. Matlab code is utilized to examine parameters affecting the performance of the brake system. The results are validated by a commercial software RecurDyn. Kriging meta model is used to reduce the computational cost of the analysis. Optimization is conducted by RecurDyn, from which the design parameters are determined that minimizes the impact at the stop.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.1
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• pp.86-93
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• 2015

Anchovy (Engraulis japonicus) is one of the most important species in the South Sea of South Korea. In order to estimate the biomass of anchovy, acoustic surveys, concurrently with trawling, were conducted in April, July, and September of 2013 and February of 2014 off the coast of Tongyeong and Yeosu. However, anchovies were found only during spring (April) and winter (February) surveys. To display only anchovy species confirmed by trawls on empty spaced echograms, virtual echograms were created. Three target strength (TS) values of anchovy were used: TS_z = 20 log L - (20/3) log (1+z/10) - 67.6 (Zhao et al.), TS_y =20 log L - 72.9 (Yoon et al.), TS_f = 20 log L - 71.9 (Foote). For anchovy schools combined with other species e.g., hairtail, squid, and Korean pomfret, their TS values were used to calculate an average TS. As a result, the anchovy biomass in the winter survey was approximately 75,000 tons (TS_z), 90,000 tons (TS_f), 114,000 tons (TS_y), respectively. The biomass in spring was 9,000 tons (TS_z), 9,200 tons (TS_f), 10,000 tons (TS_y). The sampling variance of spring was 70% and of winter was 30%. In order to manage anchovy resource sustainably, larvae and adult anchovy should be separately surveyed, the optimal area, date, and time for acoustic survey should be investigated, and the biomass survey should be done for relatively long and regular base.

• Fisheries and Aquatic Sciences
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• v.21 no.8
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• pp.24.1-24.9
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• 2018

The Korean bottom trawl survey has been deployed on a regular basis for about the last decade as part of groundfish stock assessments. The regularity indicates that they sample groundfish once per grid cell whose sides are half of one latitude and that of one longitude, respectively, and whose inside is furthermore divided into nine nested grids. Unless they have a special reason (e.g., running into a rocky bottom), their sample location is at the center grid of the nine nested grids. Given data collected by the survey, we intended to show how to appropriately estimate not only the survey index of a fish stock but also its uncertainty. For the regularity reason, we applied the systematic sampling theory for the above purposes and compared its results with a reference, which was based on the simple random sampling. When using the survey data about 11 fish stocks, collected by the spring and fall surveys in 2014, the survey indices of those stocks estimated under the systematic sampling were overall more precise than those under the simple random sampling. In estimates of the survey indices in number, the standard errors of those estimates under the systematic sampling were reduced from those under the simple random sampling by 0.23~27.44%, while in estimates of the survey indices in weight, they decreased by 0.04~31.97%. In bias of the estimates, the systematic sampling was the same as the simple random sampling. Our paper is first in formally showing how to apply the systematic sampling theory to the actual data collected by the Korean bottom trawl surveys.

• The Journal of Engineering Geology
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• v.33 no.2
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• pp.257-273
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• 2023

Hydrochemical characteristics and microbial communities of spring (Samtong), surface water, and groundwater in Cheorwon, Korea, were analyzed. Field surveys and water quality analyses were undertaken at 10 sampling points for five spring, two surface, and three groundwater samples on 15 December 2022. Hydrochemical analysis revealed that most water samples were Ca-HCO₃ type and that water-rock interactions were the predominant mineral source. Radon concentrations were <1 kBq m^-3 for surface water, 1~10 kBq m^-3 for spring water, and 1~1,000 kq m^-3 for groundwater. Microbial cluster analysis showed that the main phyla were Proteobacteria, Planctomyceta, Verrucomicrobia, Acidobacteria, and Actinomycetota.Non-metric multidimensional scaling (NMDS) analysis indicated that water temperature, pH, and Si content were closely related to microorganism content. NMDS and canonical correspondence analysis results revealed that environmental factors affecting spring water were temperature, and Mg and Si concentrations, particularly for Acidobacteria and Proteobacteria, and Pseudomonas brenneri. Both hydrochemical and microbial community analyses yielded similar results at some spring and groundwater sampling points, likely due to the effects of a basalt aquifer.

• Ocean Science Journal
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• v.43 no.3
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• pp.127-133
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• 2008

Reproductive patterns of an epifaunal amphipod, Pontogeneia rostrata, were studied on Dolsando sandy shore in Korea. The life history pattern was iteroparous, with recruitment mainly occurring from winter to spring. The sex ratio was malebiased, especially during breeding periods. The mean body length of females was significantly larger than that of males. Brood size and egg volume were positively related to the body length of ovigerous females. There was no significant difference in brood size between successive breeding periods, but egg volumes were significantly higher in early winter (December) than in late spring breeding (May and June), increasing the probability of survival to hatching. These traits contribute to more reproductive potential in early winter than in late spring breeding. The mean brood size of epifaunal P. rostrata was larger but the mean egg volume smaller than that of infaunal amphipods in this sampling area. We suggest that reproductive effort for epifaunal species may be proportionally greater than for infaunal species in risky environments.

• Journal of Environmental Health Sciences
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• v.42 no.4
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• pp.274-279
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• 2016

Objectives: We investigated bacterial diversity in the Han River water resource protection area in order to provide basic microbiological information on the drinking water safety of the Seoul metropolitan region. Methods: Samples were collected in the spring and winter, but not during the rainy season. Pyrosequencing, gene amplification, and extraction of nucleic acids were employed in this study. Results: In total, 57 and 48 operational taxonomic units were respectively analyzed in samples collected during spring and winter. Proteobacteria were predominant in all samples. The samples contained phylogenetically diverse bacterial communities, with eleven major phyla and 36 genera. Cyanobacteria were predominant in the spring samples, but not in the winter samples. The predominant species in the samples collected during both seasons belonged to the genus Aquamicrobium and Bradyrhizobium. Moreover, no pathogenic bacteria were detected in the samples. Conclusion: Proteobacteria were predominant in the samples from the Han River water source protection area. Cyanobacteria were more predominant in the spring samples than in the winter samples, but Aquamicrobium and Bradyrhizobium were predominant in both sampling seasons.

• The Journal of Engineering Geology
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• v.30 no.3
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• pp.379-397
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• 2020

In this study, Long-term change of water quality in Donrae Hot Spring was characterized using water quality data from 1922 to 2019. According to Mann-Kendall analysis and Sen's slope using long-term water quality data of Dongnae Hot Spring from 1922 to 2019, temperature, Ca, SiO₂, and HCO₃ show an increasing trend whereas EC, Na, K, Mg, Cl, and SO₄ show a decreasing trend or negligible trend. In addition, the water type of Dongnae Hot Spring stably belongs to Na-Cl type over time. The spatial distributions of water temperature and chemical constituents in 2004, 2009, 2014, and 2019 show variable patterns with showing some difference depending on sampling locations in different years. These results indicate that despite the long-term pumping of the hot spring water, the water quality is quite stable during the entire study period.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.396-401
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• 2019

A virtual rigid is modeled as the parallel structure of a virtual spring and a virtual damper. The reflective force from the virtual model is designed to be as large as possible to improve the realism of the virtual environment while maintaining the stable interaction. So, it is important to analyze the stability boundary of the virtual spring and damper. In the previous researches, the stability boundary is analyzed based on the zero-order-hold (ZOH) method, but it is analyzed based on the first-order-hold (FOH) method and the virtual damper in the paper. The boundary value of the stable virtual damper is inverse proportional to the sampling time and the maximum value of stable virtual stiffness is inverse proportional to the square of the sampling time. And the maximum value in the FOH method is increased to 110% of the value in the ZOH method. If the virtual damper is smaller than about 50% of the boundary value of the virtual damper in the FOH method, the stable virtual stiffness in the FOH method is several times larger than that in the ZOH method.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.8
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• pp.590-596
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• 2016

Biopsy is a typical needle type intervention procedure performed under radiographic image equipment such as computed tomography (CT) and cone-beam CT. This minimal invasive procedure is a simple and effective way for identifying cancerous condition of a suspicious tissue but radiation exposure for the patients and interventional radiologists is a critical problem. In order to overcome such trouble and improve accuracy in targeting of the needle, there have been various attempts using robot technology. Those devices and systems, however, are not for full procedure automation in biopsy without consideration for tissue sampling task. A robotic end-effector of a master-slave tele-operated needle type intervention robot system has been proposed to perform entire biopsy procedure by the authors. However, motorized sampling adopted in the device has different cutting speed from that of biopsy guns used in the conventional way. This paper presents the design of a novel robotic mechanism and protocol for the automation of biopsy procedure using spring-triggered biopsy gun mechanism. An experimental prototype has been successfully fabricated and shown its feasibility of the automated biopsy sequence.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.389-394
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• 2014

This paper presents the effect of a reflective force computed from a first-order-hold method on the stability of a haptic system. A haptic system is composed of a haptic device with a mass and a damper, a virtual spring, a sampler and a sample-and-hold. The boundary condition of the maximum virtual stiffness is analytically derived by using the Routh-Hurwitz criterion and the condition shows that the maximum virtual stiffness is proportional to the square root of the mass and the damper of a haptic device and also is inversely proportional to the sampling time to the power of three over two. The effectiveness of the derived condition is evaluated by the simulation. When the reflective forces are computed by using the first-order-hold method, the maximum available stiffness to guarantee the stability is increased several hundred times as large as when the zero-order-hold method is applied.