• Economic and Environmental Geology
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• v.34 no.4
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• pp.375-383
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• 2001

We extracted sea surface heights(SSH) from the TopexJPoseidon(T/P) radar altimeter data to compare with fhe SSH estimated from in-situ lide gauges(T/G) at Ulleungdo, Pohang, and SockcholMucko sites. Selection criteria such as wet/dry troposphere, ionosphere, and ocean tide were used to estimate accurate SSH. For time series analysis, the one-hour interval tide gauge SSHs were resampled al lO-day interval of the satellite SSHs. The ocean tide model applied in the altimeter data processing showed periodic aliasings of 175.5 day, 87.8 day, 62J day, 58.5 day, 49.5 day and 46.0 day, and, hence, the ZOO-day filtering was applied to reduce these spectral noises. Wavenumber correlation analysis was also applied to extract common components between the two SSHs, resulting in enhancing the correlation coefficient(CC) dramatically. The original CCs between the satenite and tide gauge SSHs are 0.46. 0.26, and 0.]5, respectively. Ulleungdo shows the largest cc bec;luase the site is far from the coast resulting in the minimun error in the satellite observations. The CCs were then increased to 0.59, 030, and 0.30, respectively, after 200.day filtering, and to 0.69, 0.63. and 0.59 after removing inversely correlative components using wavenumber correlation analysis. The CCs were greatly increased by 87, 227, and 460% when the wavenumber correlation analysis was followed by 2oo-day filtering, resulting in the final CCs of 0.86, 0.85, 0.84, respectively. It was found that the best SSHs were estimated when the two methods were applied to the original data. The low-pass filtered TIP SSHs were found to be well correlated with the TIG SSHs from tide gauges, and the best correlation results were found when we applied both low-pass filtering and spectral correlation analysis to the original SSHs.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.3
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• pp.125-130
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• 1979

In this paper, the noise pressure propagated in the air on account of the engine revolution of a stern trawler, Sae-Ba-Da(G. T. 2275.71) was measured at the check points No.1 through No.43 when the vessel was cruising, towing nets, and drifting. The experiment was carried out in the period from August 23 to October 22, 1978 at the locations of lat. $33^{\circ}$ 47'N, long. $127^{\circ}$ 34'E; lat. $34^{\circ}$ 24'N, long. $128^{\circ}$ 23'E; and lat. $6^{\circ}$ 01'N, long. $108^{\circ}$ 04'E. In case of cruising, noise on the weather deck came from funnel noise. The highest noise pressure was 92dB at observation point No.9 where tile noise pressure from main engine was 105dB when the engine was operated at 730rpm and $12^{\circ}$ sorely propeller pitch. The noise measured was reduced to 90dB at observation point No.9 when the screw propeller pitch was changed to $8^{\circ}$ that resulted in reduction of engine to 103dB. In case of towing net, the main engine revolution and screw propeller pitch was fixed at 730rpm and $8^{\circ}$ respectively. But the engine noise pressure was increased up to 106dB due to the towing resistance by 14 tons of the nets, and the noise pressure was 90dB at No.9 point. A hight noise was also generated from screw because of the towing reoistance and could be measurable even in the wall of the insulated freezing room. When the vessel was drifting: the noise pressure from the generator operated, at 720rpm was 100dB. This caused 87dB noise pressure at No.9 point. The noise pressure in the boarding or residence sections was 45 to 60dB in each case of cruisinrg towing net or drifting but it was so high as 82dB on the open deck that voice could hardly be heap.

• Journal of KIISE:Software and Applications
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• v.33 no.2
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• pp.143-153
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• 2006

Microarray which enables us to obtain hundreds and thousands of expression of gene or genotype at once is an epoch-making technology in comparative analysis of genes. First of all, we have to measure the intensity of each gene in an microarray image from the experiment to gain the expression level of each gene. But it is difficult to analyze the microarray image in manual because it has a lot of genes. Meta-gridding method and various auto-gridding methods have been proposed for this, but thew still have some problems. For example, meta-gridding requires manual-work due to some variations in spite of experiment in same microarray, and auto-gridding nay not carried out fully or correctly when an image has a lot of noises or is lowly expressed. In this article, we propose Hierarchical Grid Alignment algorithm for new methodology combining meta-gridding method with auto-gridding method. In our methodology, we necd a meta-grid as an input, and then align it with the microarray image automatically. Experimental results show that the proposed method serves more robust and reliable gridding result than the previous methods. It is also possible for user to do more reliable batch analysis by using our algorithm.

• Korean Journal of Remote Sensing
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• v.36 no.2_2
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• pp.351-363
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• 2020

It is well known that alluvial sediment located in coastal region has been easily affected by geohazard like ground subsidence, marine or meteorological disasters which threaten invaluable lives and properties. The subsidence is a sinking of the ground due to underground material movement that mostly related to soil compaction by water extraction. Thus, continuous monitoring is essential to protect possible damage from the ground subsidence in the coastal region. Radar interferometric application has been widely used to estimate surface displacement from phase information of synthetic aperture radar (SAR). Thanks to advanced SAR technique like the Small BAseline Subset (SBAS), a time-series of surface displacement could be successfully calculated with a large amount of SAR observations (>20). Because the ALOS-2 PALSAR-2 L-band observations maintain higher coherence compared with other shorter wavelength like X- or C-band, it has been regarded as one of the best resources for Earth science. However, the number of ALOS-2 PALSAR-2 observations might be not enough for the SBAS application due to its global monitoring observation scenario. Unfortunately, the number of the ALOS-2 PALSAR-2 Stripmap images in area of our interest, Busan which located in the Southeastern Korea, is only 11 which is insufficient to apply the SBAS time-series analysis. Although it is common that the radar interferometry utilizes multiple SAR images collected from same acquisition mode, it has been reported that the ALOS-2 PALSAR-2 Stripmap-ScanSAR interferometric application could be possible under specific acquisition mode. In case that we can apply the Stripmap-ScanSAR interferometry with the other 18 ScanSAR observations over Busan, an enhanced time-series surface displacement with better temporal resolution could be estimated. In this study, we evaluated feasibility of the ALOS-2 PALSAR-2 Stripmap-ScanSAR interferometric application using Gamma software considering differences of chirp bandwidth and pulse repetition frequency (PRF) between two acquisition modes. In addition, we analyzed the interferograms with respect to spectral shift of radar carrier frequency and common band filtering. Even though it shows similar level of coherence regardless of spectral shift in the radar carrier frequency, we found periodic spectral noises in azimuth direction and significant degradation of coherence in azimuth direction after common band filtering. Therefore, the characteristics of spectral bandwidth in the range and azimuth direction should be considered cautiously for the ALOS-2 PALSAR-2 Stripmap-ScanSAR interferometry.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.4
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• pp.163-168
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• 1987

The underwater observation of the ambient noise and the noise generated by the engine revolution in a ship was carried out in July to August, 1984, 1985 and 1987, near around some ports and in the Eastern Sea of Korea. Vertical distribution of the sound pressure of both noises were observed and the spectrum characteristics were analysed and compared. The results obtained are summarized as follows: 1. Sound pressure level of the ambient noise at 5m deep layer in calm sea condition (wind speed 0-2m/s) near around the ports were observed as 108dB at the eastern part of Pusan port, 106dB at the southern part of Pusan port and 101dB at Kuryongpo port. It shows that the level near around the large port which contains much noisy resources is higher than the small port. The level at 5m deep layer in the open sea, in the mid-region between Korean Peninsula and Ulnung Island was observed as 100dB. It mean that the level in the open sea is lower than that around the ports. The level at 20m and 70m deep layer were 1-2dB lower than that at 5m deep layer, and that at deeper layer than 100m was almost constantly 100dB around. 2. Sound pressure level of the ambient noise at 5m deep layer in windy open sea condition (wind speed 10-15m/s) was 108dB, and was gradually decreased in accordance with the increase of depth with representing 100dB at 70m deep layer and that at deeper layer was almost constantly 100dB. The level of the noise generated by engine revolution was 146, 125, 112, 110, 104dB at 5, 50, 100, 150 and 200m deep layer respectively. It means that the level decrease with the depth. 3. Spectrum level of the ambient noise at 5m deep layer with the frequency band of 10 Hz, 100 Hz, 1 KHz, 10 KHz, in the windy sea condition were 86, 75, 61, 32dB respectively and the level of the noise generated by engine revolution was 105, 95, 86, 55dB respectively. It means that the latter are about 20dB higher than the former. The level of the former at 200m deep layer was 80, 68, 47, 26dB and the latter 82, 70, 59, 31dB. It means that the latter are about 4dB higher than the former.

• Journal of Preventive Medicine and Public Health
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• v.17 no.1
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• pp.25-29
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• 1984

To assess the effect of noise on the blood pressure of workers, 70 weaving and 70 refining female workers in 15 to 24 years of ages were tested for the changes of blood pressure before and after exposure to the noise. The noise levels at work place were 99 dB (A) for weavers and 80 dB(A) for refiners. The mean age of refiners was 17,7 years and that of weavers was 18.6 years, and the difference in mean ages was statistically significant (p<0.05). The means of heights, weights and working durations were not significantly different between two groups. The mean systolic blood pressure of the weavers was 112.5mmHg before exposure to the noise and it was increased to 115.7mmHg after exposure to 99 dB(A) of noise for 30 minutes, and the mean diastolic blood pressure from 71.6mmHg to 74.1mmHg. These increments of blood pressure were statististically significant (p<0.05). The mean systolic blood pressure of the refiners was decreased from 108.9mmHg to 106.7mmHg after exposure to 80 dB(A) of noise for 30 minutes, and the mean diastolic blood pressure from 67.3mmHg to 67.1mmHg. These changes of blood pressure were not statistically significant. The mean systolic and diastolic blood pressure of the weavers before exposure to the noise were significantly higher than that of refiners (p<0.05). The difference of blood pressure between refiners and weavers was significantly associated with noises (p<0.05), and not ages and their interactions. The study results support the hypothesis that exposure to excessive noise increases the blood pressure of workers.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.2
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• pp.49-57
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• 2016

Even if an external forcing that will drive a climate change is given uniformly over the globe, the corresponding climate change and the feedbacks by the climate system differ by region. Thus the detection of global warming signal has been made on a regional scale as well as on a global average against the internal variabilities and other noises involved in the climate change. The purpose of this study is to estimate a timing of unprecedented climate due to global warming and to analyze the regional differences in the estimated results. For this purpose, unlike previous studies that used climate simulation data, we used an observational dataset to estimate a magnitude of internal variability and a future temperature change. We calculated a linear trend in surface temperature using a historical temperature record from 1880 to 2014 and a magnitude of internal variability as the largest temperature displacement from the linear trend. A timing of unprecedented climate was defined as the first year when a predicted minimum temperature exceeds the maximum temperature record in a historical data and remains as such since then. Presumed that the linear trend and the maximum displacement will be maintained in the future, an unprecedented climate over the land would come within 200 years from now in the western area of Africa, the low latitudes including India and the southern part of Arabian Peninsula in Eurasia, the high latitudes including Greenland and the mid-western part of Canada in North America, the low latitudes including Amazon in South America, the areas surrounding the Ross Sea in Antarctica, and parts of East Asia including Korean Peninsula. On the other hand, an unprecedented climate would come later after 400 years in the high latitudes of Eurasia including the northern Europe, the middle and southern parts of North America including the U.S.A. and Mexico. For the ocean, an unprecedented climate would come within 200 years over the Indian Ocean, the middle latitudes of the North Atlantic and the South Atlantic, parts of the Southern Ocean, the Antarctic Ross Sea, and parts of the Arctic Sea. In the meantime, an unprecedented climate would come even after thousands of years over some other regions of ocean including the eastern tropical Pacific and the North Pacific middle latitudes where an internal variability is large. In summary, spatial pattern in timing of unprecedented climate are different for each continent. For the ocean, it is highly affected by large internal variability except for the high-latitude regions with a significant warming trend. As such, a timing of an unprecedented climate would not be uniform over the globe but considerably different by region. Our results suggest that it is necessary to consider an internal variability as well as a regional warming rate when planning a climate change mitigation and adaption policy.

• Journal of the Korean earth science society
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• v.21 no.4
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• pp.408-422
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• 2000

Multiple geophysical methods were applied over the Manjang cave area in Cheju Island to compare and contrast the effectiveness of each method for exploration of underground cavities. The used methods are gravity, magnetic, electrical resistivity and GPR(Ground Pentrating Radar) survey, of which instruments are portable and operations are relatively economical. We have chosen seven survey lines and applied appropriate multiple surveys depending on the field conditions. In the case of magnetic method. two-dimensional grid-type surveys were carried out to cover the survey area. The geophysical survey results reveal the characteristic responses of each method relatively well. Among the applied methods, the electric resistivity methods appeared to be the most effective ones in detecting the Manjang Cave and surrounding miscellaneous cavities. Especially, on the inverted resistivity section obtained from the dipole-dipole array data, the two-dimensional distribution of high resistivity cavities are revealed well. The gravity and magnetic data are contaminated easily by various noises and do not show the definitive responses enough to locate and delineate the Manjang cave. But they provide useful information in verifying the dipole-dipole resistivity survey results. The grid-type 2-D magnetic survey data show the trend of cave development well, and it may be used as a reconnaissance regional survey for determining survey lines for further detailed explorations. The GPR data show very sensitive response to the various shallow volcanic structures such as thin spaces between lava flows and small cavities, so we cannot identify the response of the main cave. Although each geophysical method provides its own useful information, the integrated interpretation of multiple survey data is most effective for investigation of the underground caves.

• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.127-136
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• 2008

To identify the potential area of gas hydrate in the Ulleung Basin, 2-D and 3-D seismic surveys using R/V Tamhae II were conducted in 2005 and 2006. Seismic survey equipment consisted of navigation system, recording system, streamer cable and air-gun source. For reliable velocity analysis in a deep sea area where water depths are mostly greater than 1,000 m and the target depth is up to about 500 msec interval below the seafloor, 3-km-long streamer and 1,035 $in^3$ tuned air-gun array were used. During the survey, a suite of quality control operations including source signature analysis, 2-D brute stack, RMS noise analysis and FK analysis were performed. The source signature was calculated to verify its conformity to quality specification and the gun dropout test was carried out to examine signature changes due to a single air gun's failure. From the online quality analysis, we could conclude that the overall data quality was very good even though some seismic data were affected by swell noise, parity error, spike noise and current rip noise. Especially, by checking the result of data quality enhancement using FK filtering and missing trace restoration technique for the 3-D seismic data inevitably contaminated with current rip noises, the acquired data were accepted and the field survey could be conducted continuously. Even in survey areas where the acquired data would be unsuitable for quality specification, the marine seismic survey efficiency could be improved by showing the possibility of noise suppression through onboard data processing.

• Journal of Oral Medicine and Pain
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• v.37 no.3
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• pp.183-188
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• 2012

Previous studies of the relationship of TMJ signs and symptoms in elderly people have provided inconsistent findings. The objective of this study was to retrospectively analyze the prevalence of signs and symptoms of temporomandibular disorders(TMD). Additionally, young subjects were examined as a control group. Forty old patients (28 female, 12 male, mean age: $65.2{\pm}2.5$ years) and forty young patients (30 female, 10 male, mean age: $23.3{\pm}2.6$ years) clinically diagnosed with TMD were screened. Patient records were analyzed regarding: pain on chief complain, amount of range of mouth opening, TMJ noises(clicking sounds, crepitus), pain on palpation of the TMJ and masticatory muscles and neck and upper back muscles. Differences between the groups were assessed using t-test and the chi-squared test. (SPSS v.17) P value <0.05 was considered statistically significant. Geriatric subjects more often exhibited crepitus on mouth opening (25%), muscular palpation pain of masseter muscles (82.5%) and temporal muscles(60%). In contrast, young subjects more frequently exhibited joint sounds (62.5%), more amount of range of passive mouth opening (p=0.043). It was found that the younger subjects (82.5%) and the older subjects (87.5%) suffered from subjective sign (orofacial pain on chief complain). There were not statistically significant relationships between orofacial pain (VAS) and the groups. Differences between the groups with respect to joint sounds, muscular palpation pain and mandibular range of motion were significant. Although older subjects more frequently exhibited objective signs (crepitus on opening, pain on muscular palpation) of TMD, younger subjects more frequently objective signs (clicking sound on mouth opening, amount of mandibular range of motion).