• Journal of the Korea Institute of Building Construction
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• v.10 no.5
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• pp.95-102
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• 2010

In recent years, the demand for the development of high quality and cost effective materials, as well as the competition to ensure a diverse and sufficient amount of ready-mixed concrete, has been increasing rapidly. In this experiment, concretes made with different admixtures are blended with each other in different combinations and ratios, in order to identify potential problems. The first test was a slump level test, in which all of the concretes met the required numbers, as they also did in the test for air content. Plain organic acid concrete scored the highest in bleeding amount, but organic acid mix in general showed a similar outcome. In the early measurement of compressive strength, plain naphthalene concrete was the strongest. Of the blends, the 5:5 mix of organic acid and naphthalene was the strongest. In the standard measurement, the 5:5 mix of naphthalene and lignin was the strongest. Tensile strength tests revealed similar results. Length change rate proved to be greater in blended concrete than in plain concrete, and dry shrinkage rate was highest in the 7:3 ratio blends. Through SEM photo analysis, it was confirmed that the 7:3 ratio blends contained more micro-voids. In conclusion, with the exception of a specific few combinations, it was found that the blending of different types of concrete is undesirable due to the delayed coagulation time as well as the early decrease in strength.

• Journal of Bio-Environment Control
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• v.10 no.2
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• pp.80-87
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• 2001

This study was conducted to provide basic data for the design of shading facility of greenhouse. The proper distance between external shading screen and roof surface, transmissivity of shading materials, and shading effects of external and internal shadings were analyzed. About a distance of 10 cm between inclined external shading screen and roof surface was enough to guarantee the external shading effect in the greenhouse without roof vent. The inside temperature of greenhouse installed with 85% internal shading screen was lower the maximum of 4$^{\circ}C$ and mean of 2$^{\circ}C$ than that with 55% internal shading screen in both natural ventilation and no ventilation condition. The difference of soil temperature between shading and no shading greenhouse was great, but the difference by shading rate or shading method was small. The performance of external shading for controlling inside temperature down was superior to that of the internal shading. The externally inclined shading screen parallel to the roof surface of greenhouse was more effective than the externally horizontal shading screen in controlling inside temperature of greenhouse without roof vent.

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.13-21
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• 2016

PURPOSES : In this study, we analyzed the compressive strength characteristics of lean base concrete in relation to changes in the outdoor temperature after analyzing the cold and hot weather temperature standards and calculated the minimum and maximum temperatures when pouring concrete. We examined the rate of strength development of lean base concrete in relation to the temperature change and derived an appropriate analysis formula for FRC base structures by assigning the accumulated strength data and existing maturity formula. METHODS : We measured the strength changes at three curing temperatures (5, 20, and $35^{\circ}C$) by curing the concrete in a temperature range that covered the lowest temperature of the cold period, $5^{\circ}C$, to the highest temperature of the hot period, $35^{\circ}C$. We assigned the general lean concrete and FRC as test variables. A strength test was planned to measure the strength after 3, 5, 7, 14, and 28 days. RESULTS : According to the results of compressive strength tests of plain concrete and FRC in relation to curing temperature, the plain concrete had a compressive strength greater than 5 MPa at all curing temperatures on day 5 and satisfied the lean concrete standard. In the case of FRC, because the initial strength was substantially reduced as a result of a 30% substitution of fly ash, it did not satisfy the strength standard of 5 MPa when it was cured at $5^{\circ}C$ on day 7. In addition, because the fly ash in the FRC caused a Pozzolanic reaction with the progress into late age, the amount of strength development increased. In the case of a curing temperature of $20^{\circ}C$, the FRC strength was about 66% on day 3 compared with the plain concrete, but it is increased to about 77% on day 28. In the case of a curing temperature of $35^{\circ}C$, the FRC strength development rate was about 63% on day 3 compared with the plain concrete, but it increased to about 88% on day 28. CONCLUSIONS : We derived a strength analysis formula using the maturity temperatures with all the strength data and presented the point in time when it reached the base concrete standard, which was 5 MPa for each air temperature. We believe that our findings could be utilized as a reference in the construction of base concrete for a site during a cold or hot weather period.

• Korean Journal of Soil Science and Fertilizer
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• v.22 no.1
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• pp.12-17
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• 1989

Soil and water temperature were evaluated to relate rice growth to topographical chracteristics in paddy soils. Water temperature (WT) and so il temperature (ST) were measured under the various altitudes, slopes and irrigation methods. Temperature fluctuation and growth status in the same field were measured; 1. Air temperature (AT) and ST of 10cm soil depth were decreased with increasing altitude. Difference of its fluctuation in AT, WT and ST of 10cm soil depth in the lapse rate was 0.64, 0.84 and $0.82^{\circ}C$ per 100m elevation, respectively. 2. Maximum WT, in panicle initiation stage, was decreased slowly with increasing altitude whereas minimum WT fallen rapidly. It suggested that the lapse rate of WT was affected by minimum WT. 3. Source of irrigation water and irrigation method affected the WT. WT, ST and rice growth varied with the locations within the same field. 4. Pumping irrigation of artesian well resulted in more fluctuation of WT between irrigation intervals than did the conventional irrigation.

• The Journal of Engineering Geology
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• v.22 no.1
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• pp.27-37
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• 2012

To investigate the effect of aquifer disturbance on hydraulic properties while well drilling at unconsolidated aquifer, the following tests were conducted: the surge block and air-surging methods, which are well development methods used after well drilling; and step-drawdown tests and constant-rate pumping tests, which are used to assess changes in the aquifer after well drilling and development. The result of step-drawdown tests indicated that drawdown for a pumping-rate of $700m^3/day$ was 21.62 m after well development, decreasing 4.39 m from 26.01 m after well drilling. The skin factor used to identify the well properties decreased from 7.92 after well drilling to 5.04 after well development, respectively, which shows the improvement of well. Constant-rate pumping tests revealed a small increase in aquifer transmissivity after well development at MW-2, -3, and -4, centering around pumping well, from $1.684{\times}10^{-3}{\sim}4.490{\times}10^{-3}m^2/sec$ to $4.002{\times}10^{-3}{\sim}4.939{\times}10^{-3}m^2/sec$. MW-1, however, showed decline in hydraulic conductivity from $1.018{\times}10^{-2}m^2/sec$ to $6.988{\times}10^{-3}m^2/sec$, which was caused by a small decrease of aquifer permeability around monitoring well MW-1 due to latent factor of air interception and clogging in aquifer during surging. This finding indicates that fine particles have an effect on hydraulic properties at unconsolidated aquifers during well drilling; therefore, we consider that well drilling and development have an effect on hydraulic properties.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.4
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• pp.280-292
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• 2017

Hail is not a frequently occurring weather event, and there are even fewer reports of hail damages to forest stands. Since the 2000s, an increase in hail incidence has been documented in Europe and the United States. In Korea, severe hails occurred in Jeollanam-do province on May 31 and in Gyeongsangbuk-do province on June 1, 2017. Hail size was ranged from 0.5 to 5.0 cm in diameter in Jeollanam-do, and from 1.5 to 3.0 cm in Gyeongsangbuk-do. This study was aimed to analyze the hail damages to forests by species and topography based on damage-categorized maps created by using drones and aerial photographs, and to analyze relationships of the damages with meteorological factors. The total damaged forest area was 1,163.1ha in Jeollanam-do, and 2,942.3ha in Gyeongsangbuk-do. Among the 'severe' damaged area 326.7ha, 91% was distributed in Jeollanam-do, and concentrated in the city of Hwasun which covers 57.2% of the total 'severe' damaged area. The most heavily damaged species was Korean red pine(Pinus densiflora S. & Z.) followed by P. rigida. Most broad-leaved trees species including oaks were recovered without any dead trees found. Liliodendron tulipifera was the most severely damaged in terms of the rate of 'severe' degree individuals which are needed to be checked whether they will die or be recovered. Cause of the death of pines was considered as the combination of physical damage caused by the hail and long-lasting drought with high air temperature that occurred before and after the hail event. No pathogens and insects were found which might have affected to tree deaths. We suggested a dieback mechanism of the pine trees damaged by hail and drought.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1092-1099
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• 2022

Research on exhaust aftertreatment devices to reduce air pollutants and greenhouse gas emissions is being actively conducted. However, in the case of the particulate matters/nitrogen oxides (PM/NOx) simultaneous reduction device for ships, the problem of back pressure on the diesel engine and replacement of the filter carrier is occurring. In this study, for the optimal design of the integrated device that can simultaneously reduce PM/NOx, an appropriate standard was presented by studying the flow inside the device and change in back pressure through the inlet/outlet pressure. Ansys Fluent was used to apply porous media conditions to a diesel particulate filter (DPF) and selective catalytic reduction (SCR) by setting porosity to 30%, 40%, 50%, 60%, and 70%. In addition, the ef ect on back pressure was analyzed by applying the inlet velocity according to the engine load to 7.4 m/s, 10.3 m/s, 13.1 m/s, and 26.2 m/s as boundary conditions. As a result of a computational fluid dynamics analysis, the rate of change for back pressure by changing the inlet velocity was greater than when inlet temperature was changed, and the maximum rate of change was 27.4 mbar. This was evaluated as a suitable device for ships of 1800kW because the back pressure in all boundary conditions did not exceed the classification standard of 68mbar.

• Journal of Korean Society of Forest Science
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• v.105 no.4
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• pp.510-516
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• 2016

This study was conducted to investigate the physiological responses of newly-germinated seedlings of Fraxinus rhynchophylla Hance, Zelkova serrata (Thunb.) Makino, Betula costata Trautv. and Quercus variabilis Blume to open-field experimental warming. The seedlings in the warmed plots were warmed with $2.7^{\circ}C$ higher air temperature than those in the control plots using infrared heaters since April, 2015. Physiological responses (stomatal conductance, transpiration rate, chlorophyll content and net photosynthetic rate) to experimental warming varied with the species and the time of the measurement. Stomatal conductance ($mmol{\cdot}m^{-2}{\cdot}s^{-1}$) tended to decrease for F. rhynchophylla (Control: $158.97{\pm}42.76$; Warmed: $42.07{\pm}8.24$), Z. serrata (Control: $170.53{\pm}27.22$; Warmed: $101.17{\pm}42.27$) and B. costata (Control: $249.93{\pm}47.39$; Warmed: $150.73{\pm}26.52$). Transpiration rate ($mmol{\cdot}m^{-2}{\cdot}s^{-1}$) also decreased for F. rhynchophylla (Control: $4.08{\pm}0.62$; Warmed: $1.74{\pm}0.39$), Z. serrata (Control: $4.32{\pm}0.44$; Warmed: $3.24{\pm}1.14$) and B. costata (Control: $6.21{\pm}0.38$; Warmed: $4.66{\pm}0.28$). However, warming exhibited only minimal effects on stomatal conductance and transpiration rate of Q. variabilis seedlings. Chlorophyll content increased by the warming treatment while the effect of warming was not significant on net photosynthetic rate, since the warming treatment had a weak influence for changing net photosynthetic rate.

• Resources Recycling
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• v.13 no.1
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• pp.47-53
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• 2004

As a basic study of the re-using molten converter slag as an ordinary portland cement by conversion process, molten slag and sintered CaO pellet was reacted each other. The dissolution rate of the sintered CaO pellet into the molten slag was measured and the changes of the reaction layer was also investigated. The converter slag reagent-grade $SiO_2$ added was melted and hold for 30 minutes in MgO crucible between $1350∼1500 ^{\circ}C$. Then sintered CaO pellet heated at the same temperature was dipped into the molten slag and hold for 10∼30 min. After the reaction, the crucible was cooled in air and the specimen was cut off to the horizontal direction of the crucible. The dissolution rate of CaO pellet was measured by the change of the radius of sintered CaO pellet and the interface layer was observed by SEM/EDX and XRD. The dissolution rate of sintered CaO pellet contacted with the slag of basicity 1 was 9.8 $\mu\textrm{m}$/min at $1350^{\circ}C$ and increased to 18.0 $\mu\textrm{m}$/min at $1500^{\circ}C$. The rate was slightly decreased to 7.6 $\mu\textrm{m}$/min at $1350^{\circ}C$ and 15.0 $\mu\textrm{m}$/min at $V^{\circ}C$ in the slag of basicity 2. The dissolution rate of CaO in converter slag was followed to the rule of Arrhenius' temperature dependency, and the apparent activation energy of the dissolution of CaO was 36 kcal/mole. In case of the slag basicity of 1, the thickness of $C_2$S layer was 64-118 $\mu\textrm{m}$ and the thickness of $C_3$S was 28∼90 $\mu\textrm{m}$ for 10∼30 minutes at $1500^{\circ}C$. And the thickness of the $C_3$S layer was 90∼120 $\mu\textrm{m}$ at the same conditions in the slag basicity of 2.

• 보존과학연구
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• s.25
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• pp.119-132
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• 2004

Annals of the Joseon Dynasty is the authentic record of the historical facts and events taken place throughout the entire period of 472 years(25 generations, 1392~1863)described in a chronological order. The tremendous volume of the records contains the factual events taken place in almost all the fields of the Joseon Dynasty ranging from politics, economy to history of the dynasty. Not only because of its affluent contents but also with the precision of its records, it was designated as the National Treasure No. 151 in1973 by the Korean government and also registered as the Memory of the World by UNESCO in October 1997.This study is to report a exhaustive investigation results on the conservation state of annals of the Joseon Dynasty, especially Mt. Jeongjoksan edition, under the storage of the Kyujanggak in order to obtain the current condition, and thereby to estimate the any deterioration of the waxed volumes in the future. According to results of the investigation, we are going to verify damage causes of annals of the Joseon Dynasty, and to consider scientific conservation methods for the permanent preservation of invaluable cultural heritage. The major problem with the preservation of annals has arisen particularly from the deterioration of the waxed volumes of the Mt. Jeongjoksan edition. In order to provide for the counter measures for this problem, we have conducted twice investigations(first :1998~1999, second : 2003) to the internal and external conditions of waxed volumes(Annals of King Taejo~Annals of King Myeongjong).The result of the investigation has indicated that the paper quality of the some of the waxed volumes (Annals of King Taejong~Annals of King Sejong) is cracked and folded and the pages are imbedded to each other due to the hardened or congealed wax on the paper. Some of the pages are even getting moldy. And in order to detect as to whether“ there has been any deterioration progressed to the waxed books in the modern storage facility of the Kyujanggak equipped with constant temperature and humidity condition, the first investigation(1998~1999) and the second investigation(2003) have recorded the values of acidity, whiteness and moisture rate of the waxed paper, reporting an observation that there has been no difference on the measuring items. This indicates that no virtual deterioration has been progressed so far to the waxed volumes preserved in the Kyujanggak. Also, except for the causes of deterioration to the paper by insects and microorganisms, the major cause for the paper damage seems to the change of moisture of the paper caused from the alteration of the temperature and humidity of the storage environment. With this understanding in mind, we have conducted an environmental investigation on the three selected points of the storage in the aspects of the temperature, humidity, air current, $CO_2$,HCHO, and $SO_2$.It has been observed that the temperature stood at $16.9^{\circ}C~20.2^{\circ}C$ and the humidity was stable between 53%~56% during the period of the investigation. The concentration of the carbon monoxide and carbon dioxide of the storage were very similar to those in the air. These data lead to presume that there is no problem in the aspect of carbon oxidization. But the concentration of sulfur dioxide, hydrogen sulfide and formaldehyde of the storage were detected a little higher than those of standard. Therefore, we consider that it is necessary to ventilate the internal air of the store room by means of operating air purification devices.