• Korean Journal of Construction Engineering and Management
• /
• v.7 no.5
• /
• pp.167-176
• /
• 2006

It was found that Korean Standard of Estimate which has been used as the only basis of cost estimate of public construction projects had some side effects such as jerry-build construction and over-estimation because it failed to reflect the current price and the state-of-the-art construction methods in a changing construction environment. Therefore, the government decided to gradually introduce historical construction cost into cost estimate of public construction projects from 2004. This paper presents analytic criteria and a process model for deducing more current and reasonable historical construction cost for contract items from not only previous contract prices but also all of the other bid prices that were not contracted. The procedure of estimating actual unit cost proposed in this paper focuses on the removal of abnormal values including strategically too low or high prices and the time correction. In addition, basic research is conducted for the correction of actual unit cost through the analysis of fluctuation of bid price depending on bidding types and rates of successful bid. It is anticipated that the effective use of the proposed process model for estimating actual unit cost would make the cost estimation more current and reasonable.

• 한국태양에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.44-49
• /
• 2009

In this study, we performed urrban climate simulation how both the factor of environmental land and artificial factors influence on the formation of urban temperature. With deducing quantitative data, this study could get more accurate results of the urban temperature using urban climate simulation system. In the case of natural land cover, it appeared that there are effects on the lowering temperature and the lower temperature rate appeared in the water land cover on the whole. This is considered as temperature in water land was low because of the characteristics of water land having evaporation latent heat was high and convective sensible heat was low. In case of building which has building coverage ratio, 5% with 10 floors and building coverage ratio, 15 % with 6 floors, it appears that the temperature in the water land is $33.6^{\circ}C$. In case of building coverage ratio 5%, temperature dropped when buildings has more than 4 stories. This is regarded as the size of building is bigger, the temperature dropped in relatively because of the fluctuation of the rate of solar heat from the land. At the present time, the urban temperature are higher because of various artificial factors in the city. With these results, this study supposed to be a basies of the future studies for considering both the composition of building coverate ratio and floor plan.

• International Journal of Fluid Machinery and Systems
• /
• v.3 no.4
• /
• pp.315-323
• /
• 2010

This work investigates the influence of water compressibility on pressure pulsations induced by rotor-stator interaction (RSI) in hydraulic machinery, using the commercial CFD solver ANSYS-CFX. A pipe flow example with harmonic velocity excitation at the inlet plane is simulated using different grid densities and time step sizes. Results are compared with a validated code for hydraulic networks (SIMSEN). Subsequently, the solution procedure is applied to a simplified 2.5-dimensional pump-turbine configuration in prototype with different speeds of sound as well as in model scale with an adapted speed of sound. Pressure fluctuations are compared with numerical and experimental data based on prototype scale. The good agreement indicates that the scaling of acoustic effects with an adapted speed of sound works well. With respect to pressure fluctuation amplitudes along the centerline of runner channels, incompressible solutions exhibit a linear decrease while compressible solutions exhibit sinusoidal distributions with maximum values at half the channel length, coinciding with analytical solutions of one-dimensional acoustics. Furthermore, in compressible simulation the amplification of pressure fluctuations is observed from the inlet of stay vane channels to the spiral case wall. Finally, the procedure is applied to a three-dimensional pump configuration in model scale with adapted speed of sound. Normalized Pressure fluctuations are compared with results from prototype measurements. Compared to incompressible computations, compressible simulations provide similar pressure fluctuations in vaneless space, but pressure fluctuations in spiral case and penstock may be much higher.

• Journal of Biosystems Engineering
• /
• v.25 no.5
• /
• pp.369-378
• /
• 2000

The purpose of this study is to developed high-efficient rotary tillage system for a power tiller by improving the rotary blade. A kind of the rotary blade with single-edged blade(DS) was developed that requires lower tillage energy than conventional double-edged blade(CD) on the design theory for Japanese rotary blade. In order to find out the tillage characteristics between the single-edged blade and the double-edged blade for power tiller, experiments were performed in soil-bins which were filled up clay loam, loam and sandy loam, and then analyzed the effects of the factors such as soil texture, travelling speed, rotational speed, and tillage depth to each of the blades. And field tests were carried out to compare tillage performances of the two blades using rotary cultivator driven by conventional power tiller. The results of this study were summarized as follows; 1) On the soil bin experiment, it was found that tillage torque of the single-edged blade was less than the ones of the double-edged blade. The decreasing ratios of maximum tillage torque of the single-edged blade to the ones of the double-edged blade were 1 to 8% at clay loam, 5 to 20% at loam and 9 to 31% at sandy loam, respectively. 2) By the field tests, that the tillage performances with the single-edged blade compared with the double-edged blade was improved about 19% in field capacity, about 34% in fuel consumption, and 12.5% in soil breaking ratio. Furthermore, the fluctuation of engine speed, the variation of exhaust gas temperature, and the amount of soil clogging on the blade and straw wound on the rotary shaft showed lower values with the developed blade than the conventional blade. So, it may be concluded that tillage performance by the developed single-edged blade was improved compared with the one by the conventional double-edged blade.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.14 no.1
• /
• pp.1-13
• /
• 1986

The purpose of this study is to investigate the effect of temperature control by a shade tree and the lawn area. In this investigation, we find out that artificial-lawn, concerte, and exposed soil are more higher temperature than covered with plant materials. The results of the measurement may to summerized as follows; 1) Low-temperature effects of zoysia japonica is more controlled by condition of growth than leaf length of grass. Surface temperature make 0.7$^{\circ}C$ difference between long grass (15cm), and short grass (5cm), but make 5$^{\circ}C$ difference between good growth grass (230/10$\textrm{cm}^2$) and bad growth grass (80/10$\textrm{cm}^2$). 2) The surface temperature of the lawn area is 40.5$^{\circ}C$ lower on a maxinum than that of the artificial lawn (July 28, 1985). During the day of summer, shade area under the shade tree is 0.9$^{\circ}C$ lower then lawn area surface temperature, 6.9$^{\circ}C$ lower than bad growth lawn, 10.3$^{\circ}C$ lower than exposed soil, and 18$^{\circ}C$ lower than concrete surface temperature. 3) Natural irrigation effect on the surface temperature fluctuation. But this effect is changed by compositions of ground materials and time-lapse. 4) Sunny day is more effective than cloud day. 5) In summer season, surface temperature make a difference compare to temperature of 0.5-1.5m height from ground : Surface temperature is 3.4$^{\circ}C$ lower at the lawn area (11 a.m.), 4.2$^{\circ}C$ lower at the shade area the shade tree, 12.7$^{\circ}C$ higher at the concrete area (3p.m.), 38.8$^{\circ}C$ higher at the artificial lawn (2p.m.) 6) According to compositions of ground materials and season have specific vertical temperature distribution curve. 7) In summer season, temperature distribution of 0.5-1.5m hight at the shade tree is 4.8-5.7$^{\circ}C$ lower than concrete area (noon-3p.m.)

• Journal of Soil and Groundwater Environment
• /
• v.8 no.1
• /
• pp.81-86
• /
• 2003

Understanding the penetration behavior of the spilled oil is very important to remove itself and to minimize its impact on intertidal biological communities by earlier treatment of the oil. The purpose of this study is to clarify the effects of wave and tidal actions on the penetration of spilled oil and to evaluate main factors of oil penetration using a sandy-beach model. Infiltration processes into the sediments showed significant difference between seawater and crude oil. Seawater was infiltrated by both wave action and tidal fluctuation into the sediments in sandy beach. However, spilled crude oil penetrated into the sediments only by falling tides and not by wave action, and the first tide is most important for the penetration of stranded oil. Over 70% of bulk fraction in penetrated crude oil was concentrated to the top 2 cm sediment-layer when spilled oil volume was 1 L/$\textrm{m}^2$. Moreover, the penetration of stranded oil into the sandy beach sediments was strongly correlated with the oil viscosity affected by temperature.

• Korean Journal of Soil Science and Fertilizer
• /
• v.34 no.2
• /
• pp.92-97
• /
• 2001

Soil characteristics and crop productivity was compared between 5 soil physical treatment plots: check, reversion, subsoiling, explosive subsoiling and drainage in salt accumulated Gangseo Fine sandy loam soil from 1999 to 2000. Physical treatments of subsoil improved soil physical properties in the following order, reversion > drainage > explosive subsoiling > subsoiling > check. The effectiveness of physical treatment was sustained to the 2nd year after treatment. Soil moisture content of subsoil was highest in the reversion treatments and decreased in the order of drainage, subsoiling, and check. However there was little difference between treatments. The physical treatments increased fluctuation of soil moisture content. However the crop yield in the physical treatment plots were increased. It was considered that the increase of crop yield was caused by improvement of soil physical properties rather than soil water holding in the soil. An average increase rate of crop yield by physical treatments was 10 to 20 percent.

• Journal of Korean Society of Water and Wastewater
• /
• v.12 no.4
• /
• pp.86-96
• /
• 1998

In this study, an intermittently aerated activated sludge process, modified process from conventional activated sludge process, was developed to treat high strength swine wastewater, which has been blamed as major pollutant for stream pollution. Therefore, the optimum cycle for oxic and anoxic period, SRT, and OLR were studied as design parameters. The effects of different time interval for oxic and anoxic period on nitrification and denitrification were examined by operating two reactors with 60/60min and 60/90min as oxic/anoxic period. Although the reactor with 60/60min showed complete denitrification of $NO_x-N$ generated during oxic period, the reactor with 60/90min showed incomplete nitrification due to the inactivity of nitrifier by accumulated $NH_3-N$ toxicity during anoxic period. Therefore, it is recommended to operate same interval for oxic and anoxic period. In order to determine the optimum cycle for oxic/anoxic period, four different reactors with 30/30, 60/60, 90/90 and 120/120min were examined. The reactor operation with 90/90min was optimum to get the most stable results in this study. However, the optimum cycle for oxic and anoxic period should be changed with characteristics of influent wastewater and operating conditions. According to lie operation results of three reactors with SRT of 15, 20 and 30days. The reactor with 2Odays SRT showed best removal efficiency of T-N. The optimum OLR would be $2.5Kg\;COD/m^3/day$ which showed the most stable nitrification and denitrification. Since characteristics of influent wastewater in the real system has a severe fluctuation, so it is very difficult to determine each interval for oxic and anoxic period. Therefore, ORP curves, describing the change of oxidation/reduction potential in reactor, can be used as a control parameter for automatic control of oxic and anoxic period. In other words, bending point (Nitrate Knee) of ORP curve during anoxic period could be used as a starting point of oxic period.

• 한국해양학회지
• /
• v.1
• /
• pp.25-36
• /
• 1971

The structure of the south Korean coastal front, their fluctuation, the properties and the probable effects of the front on the mackerel fishery are discussed based on the data of 26 cruises in 1967-1969 in the southern waters of Korea. In the south Korean coastal water the annual variations of the properties shows the greatest magnitude among the other water masses in the north of East China Sea. The salinity profile provides a fairly accurate description of the interface between the two kinds of water and agree with the temperature structure in winter. The temperature front does not always coincide with the salinity front in summer, while the former corresponds to the later in winter. The sharpest and most stable front between the Tsushima Warm Current and the south Koren coastal water was found in autumn and winter. In autumn 1969, the most successful catches of mackerel was recorded in the south Korean front of great borizontal gradients of properties(temperature 5.0$^{\circ}C$/10miles, salinity 1.2 /10miles) in the east of Cheju Is. If future investigation finds the peculiar oceanographical conditions like that shown in summer, 1969, the conditions of frontal layer in coming autumn will be estimated and finally the success of the mackerel fishery will be predictable from preseason information on temperature and salinity structure in the southern waters of Korea.

• Journal of Chest Surgery
• /
• v.54 no.3
• /
• pp.200-205
• /
• 2021

Background: Various methods have been used to reduce postoperative pain after thoracic surgery. However, these methods may affect the patient's respiratory response and delay recovery from anesthesia. We aimed to evaluate the effects of fentanyl and remifentanil during extubation after video-assisted thoracic surgery (VATS). Methods: This study included 45 randomly-selected male patients who underwent VATS for pneumothorax between July 2011 and August 2012. We divided the participants into 3 groups: the F group, which received a bolus injection of 1.0 ㎍/kg of fentanyl; the R1 group, which received a 0.04 ㎍/kg/min remifentanil infusion; and the R2 group, which received a 0.08 ㎍/kg/min remifentanil infusion. Hemodynamics, pain, cough, consciousness level, and nausea were assessed for each group. Results: The number and severity of coughs were lower in the R1 and R2 groups than in the F group, and there were no differences between the R1 and R2 groups. Respiratory depression and loss of consciousness were not observed in any of the patients, and there were no differences in hemodynamics. Conclusion: In comparison with fentanyl, remifentanil did not result in a wide fluctuation of blood pressure and heart rate upon emergence from general anesthesia. Moreover, remifentanil contributed to cough suppression and postoperative pain control. Remifentanil seems to be a safe and effective analgesic after VATS.