• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.1959-1970
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• 1996

Effects of oscillatory flow upon heat transfer characteristics have been studied experimentally for oscillating flow in a circular tube. The experimental apparatus was designed to simulate the heat exchangers of the Stirling or Vuilleumier cycle machines and the test section consists of heater and cooler. Measurements were presented of heat flux, axial wall temperature distribution, and radial temperature profile of the working fluid for several cases of oscillation frequency and swept distance ratio. The influences of two main parameters, frequency and tidal displacement of the oscillation were investigated. Then the heat transfer coefficient at the heater is obtained. The carried by the authors with a assumption of oscillatory laminar slug flow.

• 한국해양학회지
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• v.1
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• pp.49-55
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• 1971

After the heavy precipitation from April 1969 to September 1970, more than 1.359 10$\^$6/㎥ of fresh water was discharged through diversion channel of the Namgang Dam. The sands and muds in the northern Sachon Bay were moved and swept away by the strong southsard flow which was observed to be speedier than five knots. The shellfish culture facility as well as the oysters and bivalves were buried. In Sachon Bay, a southward surface ebb current of approximately one knot stratifies above the northward flow of approximately 0.5 knot, which seems to be similar to the salt wedge estuary. The stratified current is responsible for the breaking of the gill nets and other fishing gears. The salinity of sea water in Chinju Bay decreased remarkably and the abnormal low salinity water lower than 5 was distributed in Sachon Bay. The low salinity water front was observed in eastern Chinju Bay and the Samchonpo Channel, where the salinity was increased from 4.6 to approximately 30 within half a tidal cycle. These caused the oysters and bivalves die, and drove anchovies and octopus out to the sea and prevented them from approaching the bay. The decrease of salinity causes the decrease of density and osmotic pressure of sea water. Turbid water would prevent the sunlight from penetrate into deep layer.

• 한국해양학회지
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• v.23 no.3
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• pp.130-145
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• 1988

Spatial distribution and temporal variations of phytoplankton population were investigated in Ch$\check{o}$nsu Bay, the Korean western coast. Diurnal fluctuations of phytoplankton standing crop are associated with semidiurnal tidal cycle, as high concentration at low tide and low at high tide. In monthly variations of phytopolankton standing crop, the 1st peak occurrs in March and the 2nd one in August. The study area could be divided into two parts, outer bay and inner bay according to the physical and biological factors such as water temperature and salinity, and phytoplankton distribution patterns. The northern waters of the bay, however, may be affected by irregular fresh water influx through the lock of the dike. Because of the hydrographical differences among the surveyed stations, phytoplankton species succession patterns of each station have some differences. On the whole in this study area, Paralia sulcata and Skeletonema costatum are dominant species all the year round. However, except June, Paralia sulcata, a tychopelagic diatom is not dominant species at Station 6 (northern end of the bay). This seems to be caused by the fact that the waters of northern part of the bay is less turbulent than that of the outer bay. The result of principal component analysis (PCA) indicates that Ch$\check{o}$nsu Bay is normal coastal ecosystem where the environmental conditions are cycled in a year, and water temperature and nitrogenous nutrients such as nitrate, nitrite and ammonia are major factors to influence the annual cycle of environmental conditions.

• Korean Journal of Remote Sensing
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• v.14 no.2
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• pp.117-128
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• 1998

Topex/Poseidon satellite, launched in Auguest 1992, has provided more 5 years of very good quality data. Efficient improvements, either about instrumental accuracy or about sea level data correction, have been made so that Topex/Poseidon has become presently a wonderful tool for many researchers. The first mission data of 73 cycles, September 1992 - August 1994, was used to our study in order to know characteristics of environmental correction factors in the Amsterdam-Crozet-Kerguelen region of the South Indian Ocean. According to standard procedures as defined under user handbook for sea surface height data processes, then we have chosen cycles 43 as the cycle of reference because this cycle has provided the completed data for measurement points and has presented the exacted position of ground track compared to another cycles. It was computed variations of various factors for correction in ascending ground track 103(Amsterdam-Kerguelen continental plateau) and descending ground track170 (Crozet basin). Here the variations of ionosphere, dry troposphere, humid troposphere, electromagnetic bias, elastic tide and loading tide were generally very smaller as a few of cm, but the variations of oceanic tide(30-35cm) and inverted barometer(15-30cm) were higher than another factors. For the correction of ocean tide, our model(CEFMO: Code d' Elements Finis pour la Maree Oceanique) - This is hydrodynamic model that is very well applicated in all oceanic situations - was used because this model has especially good solution in the coastal and island area as the open sea area. Conclusionally, it should be understood that the variation of ocean free surface is mainly under the influence of tides(>80-90%) in the Amsterdam - Crozet- Kerguelen region of the South Indian Ocean.

• Radiation Oncology Journal
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• v.26 no.3
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• pp.181-188
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• 2008

Purpose: In order to enhance the efficiency of respiratory gated 4-dimensional radiation therapy for more regular and stable respiratory period and amplitude, a respiration training system was designed, and its efficacy was evaluated. Materials and Methods: The experiment was designed to measure the difference in respiration regularity following the use of a training system. A total of 11 subjects (9 volunteers and 2 patients) were included in the experiments. Three different breathing signals, including free breathing (free-breathing), guided breathing that followed training software (guided-breathing), and free breathing after the guided-breathing (post guided-breathing), were consecutively recorded in each subject. The peak-to-peak (PTP) period of the breathing signal, standard deviation (SD), peak-amplitude and its SD, area of the one cycle of the breathing wave form, and its root mean square (RMS) were measured and computed. Results: The temporal regularity was significantly improved in guided-breathing since the SD of breathing period reduced (free-breathing 0.568 vs guided-breathing 0.344, p=0.0013). The SD of the breathing period representing the post guided-breathing was also reduced, but the difference was not statistically significant (free-breathing 0.568 vs. guided-breathing 0.512, p=ns). Also the SD of measured amplitude was reduced in guided-breathing (free-breathing 1.317 vs. guided-breathing 1.068, p=0.187), although not significant. This indicated that the tidal volume for each breath was kept more even in guided-breathing compared to free-breathing. There was no change in breathing pattern between free-breathing and guided-breathing. The average area of breathing wave form and its RMS in postguided-breathing, however, was reduced by 7% and 5.9%, respectively. Conclusion: The guided-breathing was more stable and regular than the other forms of breathing data. Therefore, the developed respiratory training system was effective in improving the temporal regularity and maintaining a more even tidal volume.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.1
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• pp.1-17
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• 2019

In this study, the surveys were carried out from October (2016) to October (2017) along the tidal flat of Geunso Bay, Taean Peninsula of the western edge of Korea. The sampling trips were carried out for a total of 16 times, once or twice a month. In order to investigate the monthly variation of the microphytobenthos (MPB) biomass, community composition and photo-physiology were analyzed by HPLC (High performance liquid chromatography). The total chlorophyll a (TChl a) concentrations used as an indicator of biomass of MPB in the upper 1 cm sediment layer ranged from 40.4 to $218.9mg\;m^{-2}$ throughout the sampling period. TChl a concentrations showed the maximum level on $24^{th}$ of February and remained high throughout March after which it started to declined. The biomass of MPB showed high values in winter and low values in summer. The monthly variations of Phaeophorbide a concentrations suggested that the low grazing intensity of the predator in the winter may have partly attributed to the MPB winter blooming. As a result of monthly variations of the MPB community composition using the major marker pigments, the concentrations of fucoxanthin, the marker pigment of benthic diatoms, were the highest throughout the year. The concentrations of most of the marker pigments except for chlorophyll b (chlorophytes) and peridinin (dinoflagellates) increased in winter. However, the concentrations of fucoxanthin increased the highest, and the relative ratios of the major marker pigments to TChl a except fucoxanthin decreased during the same period. The vertical distribution of Chl a and oxygen concentrations in the sediments using a fluorometer and an oxygen micro-optode Chl a concentrations decreased with oxygen concentrations with increasing depth of the sediment layers. Moreover, this tendency became more apparent in winter. The Chl a was uniformly vertical down to 12 mm from May to July, but the oxygen concentration distribution in May decreased sharply below 1 mm. The increase in phaeophorbide a concentration observed at this time is likely to be caused by increased oxygen consumption of zoobenthic grazing activities. This could be presumed that MPB cells are transported downward by bioturbation of zoobenthos. The relative ratios (DT/(DD+DT)) obtained with diadinoxanthin (DD) and diatoxanthin (DT), which are often used as indicators of photo-adaptation of MPB, decreased from October to March and increased in May. This indicated that there were monthly differences in activity of Xanthophyll cycle as well.

• Journal of the Korean Chemical Society
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• v.8 no.4
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• pp.192-199
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• 1964

Seasonal variations of the contents of some chemical constituents of the estuary water at two definite stations of the laver bed in Nack Dong River have been determined over one tidal cycle in spring tide from Nov. 1962 to Oct. 1963. The ranges of annual variations of the contents at station 1 and station 2 are as follows: water temp. $2.2-30.8^{\circ}C$, $3.3-28.0^{\circ}C$; pH 7.8-8.5, 7.9-8.4; chlorosity 0.025-19.66 g/l, 4.31-19.56 g/l; magnesium 0.00355-1.565 g/l, -1.524 g/l; calcium 0.00557-0.482 g/l, - -0.590 g/l; saturation % of dissolved oxygen 71.8-123.2%, 88.2-113.8%; silicate-Si 8.00-125.5 ${\mu}$g-at./l, 6.70-100.5 ${\mu}$g-at./l; phosphate-P 0.12-1.47 ${\mu}$g-at./l, 0.11-1.09 ${\mu}$g-at./l; ammonia-N 4.88-25.45 ${\mu}$g-at./l, 4.12-17.58 ${\mu}$g-at./l; nitrite-N 0.07-0.75 ${\mu}$g-at./l, 0.08-0.58 ${\mu}$g-at./l; nitrate-N 2.11-6.89 ${\mu}$g-at./l, 1.85-7.43 ${\mu}$g-at./l each. The annual tidal variations of the constituents at station 1 are more remarkable than of station 2. The chlorosity, magnesium and calcium contents are decreased nearing the slack after ebb, and increased abruptly then one hour after the slack. The contents of the other constituents are varied according to the chlorosity variety. The values of pH, chlorosity, magnesium and calcium contents are lower in summer than winter, while the difference of seasonal variations of the % saturation of dissolved oxygen is not remarkable. The phosphate-P and total nitrogen contents have a tendency of increasing within a definite range, while the silicate-Si increase proportionally, to the increasing of mixing percentage of fresh water. The average values of Si/P and N/P are several times greater than of the normal in sea water. The chemical composition considered from the value of Mg/Cl or Ca/Cl of estuarine water varies according to the variety of chlorosity, even at the high chlorosity of 19 g/l.

• Korean Journal of Remote Sensing
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• v.37 no.5_2
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• pp.1329-1340
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• 2021

The intertidal zone, which is a transitional zone between the ocean and the land, requires continuous monitoring as various changes occur rapidly due to artificial activity and natural disturbance. Monitoring of coastal topography changes using remote sensing method is evaluated to be effective in overcoming the limitations of intertidal zone accessibility and observing long-term topographic changes in intertidal zone. Most of the existing coastal topographic monitoring studies using remote sensing were conducted through high spatial resolution images such as Landsat and Sentinel. This study extracted the waterline using the NDWI from the GOCI-II (Geostationary Ocean Color Satellite-II) data, identified the changes in the intertidal area in Gyeonggi Bay according to various tidal heights, and examined the utility of DEM generation and topography altitude change observation over a short period of time. GOCI-II (249 scenes), Sentinel-2A/B (39 scenes), Landsat 8 OLI (7 scenes) images were obtained around Gyeonggi Bay from October 8, 2020 to August 16, 2021. If generating intertidal area DEM, Sentinel and Landsat images required at least 3 months to 1 year of data collection, but the GOCI-II satellite was able to generate intertidal area DEM in Gyeonggi Bay using only one day of data according to tidal heights, and the topography altitude was also observed through exposure frequency. When observing coastal topography changes using the GOCI-II satellite, it would be a good idea to detect topography changes early through a short cycle and to accurately interpolate and utilize insufficient spatial resolutions using multi-remote sensing data of high resolution. Based on the above results, it is expected that it will be possible to quickly provide information necessary for the latest topographic map and coastal management of the Korean Peninsula by expanding the research area and developing technologies that can be automatically analyzed and detected.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.3
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• pp.225-237
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• 1990

Various chemical constituents were measured from April to August 1988 at the down-ward 20 stations of Keum River, which is located in the Midwest of Korea, to understand the characteristics of water quality with respect to spatio-temporal variations of each constituent. The 24-hrs continuous measurements with 2-hrs interval were made simultaneously at station 2 near the estuary weir and station 9(Ganggyeong) of 35 km upstream from the weir in April. By the results observed for one day in April at station 2, salinity has a range of $7.88\~22.14\%_{\circ}$ and its temporal variability is identical to the pattern of tidal cycle in the neigh-bouring Kunsan Harbor. However, turbidity shows relatively high values only at an interval of 4~5 hours after the lowest salinity time, though hourly fluctuation of pH is very small. Silicate and dissolved inorganic nitrogen have inversively linear correlationships with salinity, implying the concentration of the two nutrients strongly regulated by estuarine mixing of sea and river waters. In contrast, phosphate sustains roughly a constant level over a wide salinity range and distinctly lower values than those corresponding to nitrate in the oceans. Such distributions of phosphate have been observed in some estuaries, and interpreted as driven by removal of dissolved phosphate into bottom sediments and the bufforing of phosphate by particulate matter. COD values at station 2 are relatively high in day-time(particularly afternoon) and in high-salinity periods. At station 9, saltwater intrusion was never found but water level changed to the extent of 2.5 m for one day. Although each parameter at this station exhibits very slight variations in their abundance for 24 hours compared with station 2, the contents of COD, silicate and ammonia are significantly higher than at station 2. Concentration of suspended matter is relatively high in the brackish water region up to $\~20$ km above the river mouth, probably due to strong tidal stirring of the bottom de-posits. Also, relatively high pH, COD and $O_2$ saturation at the upward stations of $40\~50$ km from the weir are presumably attributable to active photosynthesis of plants in the region. In general, COD and nutrients except phosphate are higher values at the upper stations than in the estuary zone, and show the highest abundances in July nearly at all stations. Finally, in the estuarine region tidal mixing of sea-river waters seems to be an important factor controlling the distributions of turbidity, COD, silicate and nitrate as well as salinity. However, water quality in the upward fresh-water zone is remarkably variable according to months or seasons.

• Tuberculosis and Respiratory Diseases
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• v.46 no.5
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• pp.628-635
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• 1999

Background : Maximal expiratory flow rate is determined by the size of airway, elastic recoil pressure and the collapsibility of airway in the lung. The obstruction of expiratory flow is one of the major functional impairments of emphysema, which represents COPD. Nevertheless, expiratory narrowing of upper airway may be recruited as a mechanism for minimizing airway collapse, and maintaining lung volume and hyperinflation by an endogenous positive end-expiratory pressure in patients with airflow obstruction. We investigated the physiologic role of trachea in respiration in emphysema. Method : We included 20 patients diagnosed as emphysema by radiologic and physiologic criteria from January to August in 1997 at Seoul Municipal Boramae Hospital. Chest roentgenogram, high resolution computed tomography(HRCT), and pulmonary function tests including arterial blood gas analysis and body plethysmography were taken from each patient. Cross-sectional area of trachea was measured according to the respiratory cycle on the level of aortic arch by HRCT and calibrated with body surface area. We compared this corrected area with such parameters of pulmonary function tests as $PaCO_2$, $PaO_2$, airway resistance, lung compliance and so on. Results : Expiratory cross-sectional area of trachea had significant correlation with $PaCO_2$ (r=-0.61, p<0.05), $PaO_2$ (r=0.6, p<0.05), and minute ventilation (r=0.73, p<0.05), but inspiratory cross-sectional area did not (r=-0.22, p>0.05 with $PaCO_2$, r=0.26, p>0.05 with $PaO_2$, and r=0.44, p>0.05 with minute ventilation). Minute ventilation had significant correlation with tidal volume (r=0.45, p<0.05), but it had no significant correlation with respiratory frequency (r=-0.31, p>0.05). Cross-sectional area of trachea had no significant correlation with other parameters of pulmonary function including $FEV_1$, FVC, $FEV_1$/FVC, peak expiratory flow, residual volume, diffusing capacity, airway resistance, and lung compliance, whether the area was expiratory or inspiratory. Conclusion : Cross-sectional area of trachea narrowed during expiration in emphysema, and its expiratory area had significant correlation with $PaCO_2$, $PaO_2$, and minute ventilation.