• Proceedings of KOSOMES biannual meeting
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• 2003.11a
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• pp.157-162
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• 2003

The sludge oils were produced necessarily in the ships operation, so that it will be the best way to manage the sludge oils inside ship itself from a viewpoint of the prevention of marine oil pollution from ship. The ultrasonic breaking systems which recycle the sludge oil from ship into usable oil to be brunt is recognized as a most possible recycling device. In this regards, the purpose of this study is to examine erosion damage on the SS400 specimen by cavitation and the effect of impact pressure generated from the demolition of the cavity of ultrasonic vibration in the marine sludge oil environment .. The erosion damage of specimen was investigated mainly on weight loss, weight loss rate and maximum erosion rate with variation of the oil temperature as well as the change of space between transducer horn and specimen. The experimental results showed that as the space between ultrasonic vibrator horn and specimen disk increased, the weight loss and weight loss rate decreased and the values were larger in SFO than in SLO. The experimental results can be useful to the development of sludge oil disposing systems and to consider a countermeasure for the prevention of erosion damages by cavitation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.92-100
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• 2018

Vortical systems are considered a main feature to sustain turbulence in a boundary layer through interaction. Such turbulent structures result in frictional drag and erosion or vibration in engineering applications. Research for controlling turbulent flow has been actively carried out, but in order to show the effect of vortices in a turbulent boundary layer, it is necessary to clarify the mechanism by which turbulent energy is transferred. For this purpose, it is convenient to demonstrate and capture phenomena in a laminar boundary layer. Therefore, in this study, the interactions of disturbed flow around a hemisphere on a flat plate in laminar flow were analyzed. In other words, a street of hairpin vortices was generated following a wake region formed after flow separation occurred over a hemisphere. Necklace vortices surrounding the hemisphere also appeared due to a strong adverse pressure gradient that brought high momentum fluid into the wake region thereby leading to an increase in the frequency of hairpin vortices. To mitigate the effect of these necklace vortices, local suction control was applied through a hole in front of the hemisphere. Flow visualization was recorded to qualitatively determine flow modifications, and hot-film measurements quantitatively supported conclusions on how much the power of the hairpin vortices was reduced by local wall suction.

• Asian Journal of Atmospheric Environment
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• v.12 no.2
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• pp.109-126
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• 2018

This paper presents seasonal variation of $PM_{10}$ over five urban sites in Sabah, Malaysia for the period of January through December 2012. The variability of $PM_{10}$ along with the diurnal and weekly cycles of CO, $NO_2$, $SO_2$, and $O_3$ at Kota Kinabalu site were also discussed to investigate the possible sources for increased $PM_{10}$ concentration at the site. This work is crucial to understand the behaviour and possible sources of $PM_{10}$ in the urban atmosphere of Sabah region. In Malaysia, many air pollution studies in the past focused in west Peninsular, but very few local studies were dedicated for Sabah region. This work aims to fill the gap by presenting the descriptive statistics on the variability of $PM_{10}$ concentration in the urban atmosphere of Sabah. To further examine its diurnal and weekly cycle pattern, its responses towards the variations of CO, $NO_2$, $SO_2$, and ozone were also investigated. The highest mean value of $PM_{10}$ for the whole study period is seen from Tawau ($35.7{\pm}17.8{\mu}g\;m^{-3}$), while the lowest is from Keningau ($31.9{\pm}18.6{\mu}g\;m^{-3}$). The concentrations of $PM_{10}$ in all cities exhibited seasonal variations with the peak values occurred during the south-west monsoons. The $PM_{10}$ data consistently exhibited strong correlations with traffic related gaseous pollutants ($NO_2$, and CO), except for $SO_2$ and $O_3$. The analysis of diurnal cycles of $PM_{10}$ levels indicated that two peaks were associated during the morning and evening rush hours. The bimodal distribution of $PM_{10}$, CO, and $NO_2$ in the front and at the back of ozone peak is a representation of urban air pollution pattern. In the weekly cycle, higher $PM_{10}$, CO, and $NO_2$ concentrations were observed during the weekday when compared to weekend. The characteristics of $NO_2$ concentration rationed to CO and $SO_2$ suggests that mobile sources is the dominant factor for the air pollution in Kota Kinabalu; particularly during weekdays.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.757-764
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• 2019

Depressurization occurs around underwater objects moving at high speeds. This causes cavitation nuclei to expand, resulting in cavitation. Cavitation is accompanied by an increase in noise and vibration at the site, particularly in the case of thrusters, and this has a detrimental ef ect on propulsion performance. Therefore, predicting cavitation is necessary. In this study, an analytical method for cavitation noise is developed and applied to an elliptic wing. First, computational fluid dynamics are performed to obtain information about the flow fields around the wing. Then, through the cavitation nuclei density function, number of cavitation nuclei is calculated using the initial radius of the nuclei and nuclei are randomly placed in the upstream with large pressure drop around the wing tip. Bubble dynamics are then applied to each nucleus using a Lagrangian approach for noise analysis and to determine cavitation behavior. Cavitation noise is identified as having the characteristics of broadband noise. Verification of analytical method is performed by comparing experimental results derived from the large cavitation tunnel at the Korea Research Institute of Ships & Ocean Engineering.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.64.3-65
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• 2016

The NISS (Near-infrared Imaging Spectrometer for Star formation history) is the near-infrared instrument optimized to the Next Generation of small satellite series (NEXTSat). The capability of both imaging and low spectral resolution spectroscopy in the near-infrared range is a unique function of the NISS. The major scientific mission is to study the cosmic star formation history in local and distant universe. For those purposes, the main observational targets are nearby galaxies, galaxy clusters, star-forming regions and low background regions. The off-axis optical design is optimized to have a wide field of view ($2deg.{\times}2deg.$) as well as the wide wavelength range from 0.95 to $3.8{\mu}m$. Two linear variable filters are used to realize the imaging spectroscopy with the spectral resolution of ~20. The mechanical structure is considered to endure the launching condition as well as the space environment. The compact dewar is confirmed to operate the infrared detector as well as filters at 80K stage. The electronics is tested to obtain and process the signal from infrared sensor and to communicate with the satellite. After the test and calibration of the engineering qualification model (EQM), the flight model of the NSS is assembled and integrated into the satellite. To verify operations of the satellite in space, the space environment tests such as the vibration, shock and thermal-vacuum test were performed. Here, we report the test results of the flight model of the NISS.

• Journal of the Korea Society of Computer and Information
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• v.19 no.3
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• pp.1-9
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• 2014

In this paper, we design and implement location information system and user mapping system using DSDV(Destination Sequenced Distance Vector) routing algorithm in ad-hoc network environment to efficient manage a number of mobile devices. The software part in proposed system construct ad-hoc network using DSDV routing algorithm and it activate alarm system, such as vibration, when one of devices disappears in the network. The hardware system, called u_LIN (User Location Information Node) construct ad-hoc network and it helps to find a disappeared device by using warning system. When we evaluate the performance of our prototype system, we have checked a correct operation, within the range of 250m in case of 1:1 communication and within the range of 100m in case of 1:N communication. The implemented system in this paper is highly expected to flexibly use in juvenile protection system, stray-child protection system, tourist guide system and so on.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.40.1-40.1
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• 2017

The NISS (Near-infrared Imaging Spectrometer for Star formation history) is the near-infrared spectro-photometric instrument optimized to the Next Generation of small satellite series (NEXTSat). To achieve the major scientific objectives for the study of the cosmic star formation in local and distant universe, the spectro-photometric survey covering more than 100 square degree will be performed. The main observational targets will be nearby galaxies, galaxy clusters, star-forming regions and low background regions. The off-axis optics was developed to cover a wide field of view ($2deg.{\times}2deg.$) as well as the wide wavelength range from 0.95 to $2.5{\mu}m$, which were revised based upon the recent test and evaluation of the NISS instrument. The mechanical structure were tested under the launching condition as well as the space environment. The signal processing from infrared sensor and the communication with the satellite were evaluated after the integration into the satellite. The flight model of the NSS was assembled and integrated into the satellite. To verify operations of the satellite in space, the space environment tests such as the vibration, shock and thermal-vacuum test were performed. The accurate calibration data were obtained in our test facilities. Here, we report the test results of the flight model of the NISS.

• Journal of Environmental Health Sciences
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• v.22 no.3
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• pp.37-48
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• 1996

The purpose of this study is to provide the valuable basic information that helps set the advanced direction of study in environmental pollution in the future. It classifies and analyzes 6, 531 papers according to their years, fields, and contents from 1962 to 1993 in Korea through Chunrian, a PC communication network, National Environment Research Institute(1989) in Seoul. Classifying papers by their fields, this study shows 19.6%(1, 281 papers) of total papers on water pollution, on which most emphasis was placed in the studies, 17.2%(1, 121 papers) on general remarks, 14.6%(952 papers) on environmental ecology, and 13.6%(891 papers) on air pollution. Classifying papers by their contents, this study tells us that the survey of state and evaluation of pollution degree took 28%(1, 829 papers) of total papers, and it seemed the most active study was carried out on this content. It then shows us that the treatment technology and mechanism shared 17.5%(1, 144 papers), and facilities and design took 1.9%(127 papers) which needed more studies in the future. As for the trends of study, the papers published until 1979 show that the water pollution accounted for 28.9% of total studies, on which the greatest emphasis was placed, while the papers in 1990s tell us that general remarks 34.7%, air pollution 14.9%, and water pollution 14.1%. It also shows that treatment technology and mechanism has had more importance since 1980s in water pollution, noise and vibration, waste materials, human wastes, and radioactive pollution. However, in sea pollution, policy and standard rather than treatment technology or method of measurement and analysis has been considered a more important one in 1990s. Analyzing the studies on general remarks, it tell us that the paper on environmental act, which were frequently conducted, accounted for 33.3% until 1979, while the papers on the environmental policy, in which the highest interest was kept, accounted 34.6% in 1990s. This study concludes that most papers had examined the survey on status and evaluation of pollution degree before 1980, while studies on solving the problems of environmental pollution have had more importance in the 1980s and 1990s. Therefore, in the future, more studies should be conducted actively on policy development to solve the problems of environment pollution as well as on encouragement of environmental consciousness.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.1
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• pp.40-48
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• 2009

Leading of the computer, IT technology has make great strides. As a information-industry-community was highly developed, user's needs to convenience about intelligence and humanization of interface is being increase today. Nowadays, researches with are related to BCI are progress put the application-technology development first in importance eliminating research about fountainhead technology with DB construction. These problems are due to a BCI-related research studies have not overcome the initial level, and not toward a systematic study. Brain wave are collected from subjects is a signal that the signal is appropriate and necessary in the experiment is difficult to distinguish. In addition, brain wave that it's not necessary to collect the experiment, serious eyes flicker, facial and body movements of an EMG and electrodes attached to the state, noise, vibration, etc. It is hard to collect accurate brain wave was caused by mixing disturbance wave in experiment on the environment. This movement, and the experiment of subject impact on the environment due to the mixing disturbance wave can cause that lowering cognitive and decline of efficiency when embodied BCI system. Therefore, in this paper, we propose an accurate and efficient brain-wave DB building system that more exactness and cognitive basis studies when embodied BCI system with brain-wave. For the minimize about brain wave DB with mixing disturbance, we propose a DB building method using an automatic control and prevent unnecessary action, put to use the subjects face tracking.

• Journal of Digital Contents Society
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• v.17 no.2
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• pp.71-79
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• 2016

This study is intended to compare the performances of sound source localization methods used for stable automobile control by improving voice recognition rate in automobile environment and suggest how to improve their performances. Generally, sound source location estimation methods employ the TDOA algorithm, and there are two ways for it; one is to use a cross correlation function in the time domain, and the other is GCC-PHAT calculated in the frequency domain. Among these ways, GCC-PHAT is known to have stronger characteristics against echo and noise than the cross correlation function. This study compared the performances of the two methods above in automobile environment full of echo and vibration noise and suggested the use of a median filter additionally. We found that median filter helps both estimation methods have good performances and variance values to be decreased. According to the experimental results, there is almost no difference in the two methods' performances in the experiment using voice; however, using the signal of a song, GCC-PHAT is 10% more excellent than the cross correlation function in terms of the recognition rate. Also, when the median filter was added, the cross correlation function's recognition rate could be improved up to 11%. And in regarding to variance values, both methods showed stable performances.