• Tuberculosis and Respiratory Diseases
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• v.46 no.6
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• pp.803-810
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• 1999

Background : The patient's work of breathing(WOBp) during assisted ventilation may vary according to many factors including ventilatory demand of the patients and applied ventilatory setting by the physician. Pressure-controlled ventilation(PCV) which delivers gas with decelerating flow may better meet patients' demand to improve patient-ventilator synchrony compared with volume-controlled ventilation(VCV) with constant flow. This study was conducted to compare the difference in WOBp in two assisted modes of ventilation, PCV and VCV with constant flow. Methods : Ten patients with respiratory failure were included in this study. Initially, the patients were placed on VCV with constant flow at low tidal volume($V_{T,\;LOW}$)(6-8 ml/kg) or high tidal volume($V_{T,\;HIGH}$)(10-12 ml/kg). After a 15 minute stabilization period, VCV with constant flow was switched to PCV and pressure was adjusted to maintain the same tidal volume($V_T$) received on VCV. Other ventilator settings were kept constant. Before changing the ventilatory mode, WOBp, $V_T$, minute ventilation($V_E$), respiratory rate(RR), peak airway pressure (Ppeak), peak inspiratory flow rate(PIFR) and pressure-time product(PTP) were measured. Results : The mean $V_E$ and RR were not different between PCV and VCV during the study period. The Ppeak was significantly lower in PCV than in VCV during $V_{T,\;HIGH}$. HIGH ventilation(p<0.05). PIFR was significantly higher in PCV than in VCV at both $V_T$ (p<0.05). During $V_{T,\;LOW}$ ventilation, WOBp and PTP in PCV($0.80{\pm}0.37\;J/min$, $164.5{\pm}74.4\;cmH_2O.S$) were significantly lower than in VCV($1.06{\pm}0.39J/mm$, $256.4{\pm}107.5\;cmH_2O.S$)(p<0.05). During $V_{T,\;HIGH}$ ventilation, WOBp and PTP in PCV($0.33{\pm}0.14\;J/min$, $65.7{\pm}26.3\;cmH_2O.S$) were also significantly lower than in VCV($0.40{\pm}0.14\;J/min$, $83.4{\pm}35.1\;cmH_2O.S$)(p<0.05). Conclusion : During assisted ventilation, PCV with decelerating flow was more effective in reducing WOBp than VCV with constant flow. But since individual variability was shown, further studies are needed to confirm these results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6B
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• pp.565-575
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• 2011

The purpose of this study was to quantitatively evaluate the expression of both multi-metric qualitative habitat evaluation index (QHEI) and biological integrity index (IBI) for artificial structures eco-artificial fish reef (EAFR) for fishes asylum and habitat. Especially, both experimental evaluation and biological verification were performed in Water and Environmental Center's outdoor test-bed of Korea Institute of Construction Technology located in Andong-city, Gyeongsangbuk-do. The experimental conditions reflecting the situation of domestic river include the flow rate (e.g., $0.0{\sim}1.5m\;s^{-1}$), the width (e.g., 1.0~3.0 m), the depth (e.g., 0.05~0.70 m), and variable bed materials. Both QHEI and IBI were monitored for 8 months from May to December 2010. Whereas QHEI values were highest at experimental points of the E~F with an average of 83.1, those were lowest at B~C with an average of 78.1. However, QHEI values inside EAFR were more than 98.9, regardelss of space and time, and indicated more than the highest good of the state (Good) in the habitat. Overally, IBI values showed similar trend with QHEI, but were 44.2 in the winter dry season, compared to 32.8 of QHEI values. IBI values Also, IBI values inside EAFR were greater than those at the experimental channel by 5.7 to 11.4% and 18.7 to 34.8% in flow and stagnant conditions, respectively, indicating that EAFR can secure asylum and habitat for fish during the dry season. For comprehensive aquatic ecosystem assessment, the experimental channel showed generally fair conditions (Fair~Good), whereas EAFR showed good conditions (Good), suggesting that EAFR can be applied to aquatic ecosystem restoration and improvement.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.255-265
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• 1999

CTD castings and current observations are taken in June, July and October, 1997 and May and July, 1998 to investigate the effect of the Keum River dyke on the structure of physical properties and the type of the Keum River estuary. Tide and tidal current relation shows that the ebbing is longer than the flooding by 1.5 hours with the early current reversing before high tide. In the rainy season (May to July), frequent large fresh water discharge during the ebbing from the dyke changes vertical salinity difference and time variation of salinity greatly near the head of the estuary, where salinity becomes lower than 2‰ in summer fresh water flooding. Halocline developed by the fresh water discharge makes two-layer structure, of which strength and depth increase in the low tide. The relationship between tide phase and surface salinity variation shows the phase lag of 2.5 hours near the head of the estuary but the standing wave relation down the estuary. This phase lag implies that a low salinity water diluted by the fresh water discharge for 2-3 hours in the ebb period moves with tidal excursion. In the dry season, vertical salinity difference reduces significantly. We calculate stratification and circulation parameters using the observed salinity structure, surface current and fresh water discharge. The Keum River estuary shows a partially mixed type, changing the stratification parameter from the rainy to the dry season. Mean flows of observed tidal current at lower and upper layer are landward and seaward, which are consistent with the circulation of a partially mixed estuary. Based upon the estuary type and circulation we suggest that the suspended materials will move toward the upstream due to low-layer mean flow and then the Keum River estuary will be a deposit environment.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.1
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• pp.1-12
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• 2013

Acoustic backscatter profiles were measured by Eco-sounder along an east-west section in the mid-eastern Yellow Sea and at an anchoring station in the low salinity region off the Keum River estuary in September 2012, with observing physical water property structure by CTD. Tidal front was established around the sand ridge developed in 50 m depth region. Internal waves measured by Eco-sounder during low tide period in the eastern side of the sand ridge were nonlinear depression waves with wave height of 15 m and mean wavelength of 500 m. These waves were interpreted into tidal internal waves that were produced by tidal current flowing over the sand ridge to the southeast. When weakly non-linear soliton model was applied, propagation speed and period of these internal depression wave were 50 m/s and 16~18 min. Red tides by Dinoflagelates Cochlodinium were observed in the sea surface where strong acoustic scattering layer was raised up to 7 m. Hourly CTD profiles taken at the anchoring station off the Keum River estuary showed the halocline depth change by tidal current and land-sea breeze. When tidal current flowed strongly to the northeast during flood period and land-breeze of 7 m/s blew to the west, the halocline was temporally raised up as much as 2 m and acoustic profile images showed a complex structure in the surface layer within 5-m depth: in tens of seconds the declined acoustic structure of strong and weak scattering signals alternatively appeared with entrainment and intrusion shape. These acoustic profile structures in the surface mixed layer were observed for the first time in the coastal sea of the mid-eastern Yellow Sea. The acoustic profile images and turbidity data suggest that relatively transparent low-layer water be intruded or entrained into the turbid upper-layer water by vertical shear between flood current and land breeze-induced surface current.

• Ecology and Resilient Infrastructure
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• v.4 no.3
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• pp.169-179
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• 2017

This study analyzed the aspect of bed change according to the stable channel design on the Wonju River to quantitatively evaluate habitat suitability (HS). According to the result of evaluating stable channel of object section in the Wonju River, 17 sections among total 20 sections were stable and 3 sections were unstable. Physical disturbance improvement evaluation (PDIE) was the range average showed good disturbance condition with a range average of 112.17 points. Habitat suitability index of Zacco Koreanus, the most dominant species of the Wonju River, was used for analysis of physical habitat for fish. According to the physical habitat analysis result, HS was 0.16 and weighted usable area (WUA) was $347.68m^2$. The methods of improving/introducing/removing structures and dredging stream channel were used for stable channel design of unstable channel, and analyzed PDIE according to the aspect of bed change and changes in habitat suitability. Stable channel design was possible in 19 sections in times of structures improvement/introduction/removal, and PDIE was 117.53 points, HS was 0.14 points, and WUA was $313.37m^2$. Stable channel design was possible in all 20 sections when dredging the stream channel. PDIE was 116.50 points, HS was 0.16, and WUA was $332.14m^2$. Therefore, this study obtained channel design measures that can improve physical soundness and stability of the Wonju River, and it was analyzed that it will have no impact on changes of physical disturbance and physical habitat. Furthermore, this study analyzed velocity and depth of each section and appearance frequency of riffle and pool to analyze correlation between physical disturbance and physical habitat. According to the analysis result, it was identified that the analysis of riffle and pool showed similar result as the evaluation result of physical habitat.

• Magazine of the Korean Society of Agricultural Engineers
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• v.14 no.3
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• pp.2703-2715
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• 1972

1. Title of Research Research on the Loss of Irrigation Water Flowing in Earth Channel. 2. Purpose and Importance of Research The purpose of this research is to obtain the accurate loss rated of irrigation water flowing in earth channels so as to give a criterion of designing rational and effective suplpy project of irrigations water. It is the present status that the loss rates of 10 to 20% are obscurely applied without any scientific proof. Therefore, the importance of this research lies in securing loss rates, which are experimentally proves to be suitable for specific local conditions. 3. Content and Scope of Research The selected test reach of the main channel is 1,000m long. Discharges were measured at up and downstream enps by using current meter. The test reach of the lateral channel is 500m long, and parshall flumes were set at both ends to measure inflow and outflow. Finally, for the supply ditch, the test section is 200m long, and sharp-edged rectangular weirs were provided at both ends to measure inflow and outflow. In addition, various factors influence on the loss of irrigation water in channel wer examined. 4. Results of Research and Proposition Results: 1. In the main channel, which is 1,000 M long, and has a slope of 1/3,000 and was constructed by cutting earth, its loss rate is 9.64%. 2. In the lateral, which has a slope of 1/1,500, and is 500m long, and was constructed by cutting, its loss rate is 15.55%. Its average seepage rate is 2.08cm/day. 3. In the supply ditch, which has a slope of 1/300, and is 200m long, and was constructed by filling earth, its loss rate is 12.34%, its average seepage rate being 3.37cm/day. Proposition: As could be seen in the results above-mentioned, it is contradictory to apply a loss rate of 20% for every main channels and 15% for every laterals without variation, as done so for in planning irrigation project. The fact, however, is that loss rates must be different according to localities and characteristics. Due to the fact that this experiment is small in its scope and is nothing but a preliminary one, it is hardly possible to draw decisive conclusions with the results obtained in this research. Loss rates, that are secured through more extensive research, should be used, in order to establish precise irrigation project. Moreover, such researches should be carried out for a number of loclities throughout the nation.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.295-302
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• 2014

This study demonstrates a double-path CDI as an alternative of advanced wastewater treatment process. While the CDI typically consists of many pairs of electrodes connected in parallel, the new double-path CDI is designed to have series flow path by dividing the module into two stages. The CFD model showed that the double-path had uniform flow distribution with higher velocity and less dead zone compared with the single-path. However, the double-path was predicted to have higher pressure drop(0.7 bar) compared the single-path (0.4 bar). From the unit cell test, the highest TDS removal efficiencies of single- and double-path were up to 88% and 91%, respectively. The rate of increase in pressure drop with an increase of flow rate was higher in double-path than single-path. At 70 mL/min of flow rate, the pressure drop of double-path was 1.67 bar, which was two times higher than single-path. When the electrode spacing was increased from 100 to $200{\mu}m$, the pressure drop of double-path decreased from 1.67 to 0.87 bar, while there was little difference in TDS removal. When proto type double-path CDI was operated using sewage water, TDS, $NH_4{^+}$-N, $NO_3{^-}$-N and $PO_4{^{3-}}$-P removal efficiencies were up to 78%, 50%, 93% and 50%, respectively.

• Journal of Korean Society of Forest Science
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• v.49 no.1
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• pp.11-31
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• 1980

The morphological, anatomical and physiological traits were eximined for Populus alba ${\times}$ glandulosa which is an important planting species in Korea. The results obtained are as follows: 1. External characters in the leaf shape and chaff shape in the catkin were inherited as incomplete dominance but nectar gland was inherited as dominance. 2. Among the 15 selected clones, 9 clones were male, 2 clones female and 2 clones monoecious. 3. There were well-developed cork layers and bast fiber bundles in the bark. 4. Primordial leaves composed of 3 layers of cells and those undifferentiated into palisade and spongy parenchymas differed in its origin. 5. Leaf scare consisted of two kinds of tissues; one is connected to vascular bundle and the other not to vascular bundle. Tissues which had been connected to vascular bundle were isolated with only 2 or 3 layers of cork cells from the outside. 6. There was complicated arrangement in the vascular bundle of petioles. 7. Growth of the hybrid was sensitively influenced by external temperature, day-length and amount of light. In particular, it was apparent in height growth. 8. Flatness, loam soils and a $60{\times}60cm$ spacing might be best factors for the growth of P. alba ${\times}$ glandulosa. 9. The rooting of 15 clones was dependant upon external factors. 10. The growth of P. alba ${\times}$ glandulosa was best at around 80% of soil moisture content on the basis of plot water capacity. 11. Temperature difference between inside and outside stems below 100cm during the winter was the greatest at the south among seasons and among directions. 12. The sap movement was markedly influenced by air temperature, relative humidity in forest stand and moisture content in stem. 13. Total sugars in the cortex changed with season but did not differ in the dircetion of the stem. 14. Isoperoxidase variations in the leaf were different among 15 clones. Thus, it may be useful as a criterium for clonal identification. 15. The rate of soil moisture content decreased at a rapid slope was faster than that at a slow slope. Poor growth of P. alba ${\times}$ glandulosa at the slope was probably due to depletion of soil moisture.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.468-477
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• 2019

The numerical model of Boussinesq approximation, which is mainly used for evaluating the port calmness due to the irregular waves, has a limit of applicability of lattice size in ports such as marinas with narrow port openings of around 30m. The SWASH model controls the partial reflection according to the depth, porosity coefficient and structure size when applying the reflected wave incident on the structure and terrain. In this study, the partial reflection evaluation at the front of the structure according to the bottom shape and the shape of the structure are examined. In order to evaluate the reproducibility of the model due to the diffraction waves entering the term, the area of incidence at right angles and inclination of the structure is constructed and compared with the diffraction theory suggested by Goda et al. (1978). The experimental results of the sectional structure reflectances calculated as the depth mean show reflectances similar to the approximate values of the reflectances presented by Stelling and Ahrens (1981). It is considered that the reflected wave is well reproduced according to the control of the reflected wave at the boundary and the shape and topography of the structure. Compared with previous studies to examine the diffraction of the wave incident from the breakwater opening, the wave incidence angle and the shape of the diffraction wave are very similar to the theoretical values, but both oblique and rectangular incidence In the case where the direction concentration is small, the diffraction degree is underestimated in some sections with the crest ratio of 0.5 to 0.6.

• Journal of Wetlands Research
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• v.19 no.2
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• pp.252-258
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• 2017

To determine the effects of small dam on benthic macro-invertebrate community, benthic macro-invertebrates were surveyed with both quantitative and qualitative collecting methods from 4 sites at a terraced interval (3.02 small dams per 100 m) and from 5 sites at a non-terraced interval (0.96 small dams per 100 m) in upper reach of Dorim stream, Seoul. The average water flow rate was higher at the non-terraced interval (0.149 m/s) than at the terraced interval (0.043 m/s). Diptera, which prefer slow water flow or lentic habitats, appeared more abundantly in the terraced interval (78.3%) than in the non-terraced interval (32.0%)(p<.05). Ephemeroptera, which prefer fast water flow or lotic habitats, appeared more abundantly in the non-terraced interval (14.1%) than in the terraced interval (4.5%)(p=.203). There was a difference in species distribution of Trichoptera in terraced and non-terraced intervals depending on preferred environment. In the terraced interval, the occupancy ratio of gathering-collector was 1.8 times higher than in the non-terraced interval (p<.05). In contrast, filtering-collector appeared to be about 4.4 times higher rate in the terraced interval (p=.124). The evenness indexes (J′) were found to be 0.41 and 0.77, respectively in terraced area and non-terraced intervals. KSI, evaluating biological water quality, showed an average of 4.0 and 2.4 respectively in terraced and non-terraced intervals. EPT/C index, indicating the balance of the community, showed an average of 0.1 and 0.7 respectively in terraced and non-terraced intervals. It suggests that we should make small dams in order to maintain biodiversity of benthic macro-invertebrates.