• Resources Recycling
• /
• v.14 no.4 s.66
• /
• pp.34-40
• /
• 2005

Reusing of electroless Co-Cu-P waste solution was investigated in the respect of plating time, plating rate, solution composition and deposit. Plating time of cobalt-catalytic surface took longer than that of zincated-catalytic surface. It was possible to reuse the waste solution by mixing $50\%$ fresh solution at batch type. Plating time of initial solution at continuous type took longer 7.5 times over than that of batch type. Plating time of $50\%$ waste solution additive at continuous type took longer 2.5 times over than that of batch type. Component change of cobalt-topper for electroless deposition was greatly affected by deposit inferiority and rapid decrease in plating rate.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.6
• /
• pp.122-129
• /
• 2013

Since electrical resistivity of concrete can be measured in a more rapid and simple way than chloride diffusivity, it should be primarily regular quality control of the electrical resistivity of concrete which provides the basis for indirect of quality control of chloride diffusivity during concrete construction. If this is realized, the electrical resistivity of concrete can be a crucial parameter to establish maintenance strategy for marine concrete structures. The purpose of this study is to develop, design and test a surface electrical resistivity measurement protocol. Microstructural affecting factors such as capillary water, porosity, tourtousity, and so on, on the electrical resistivity of concrete were examined taking into account for mixing proportion properties, and hydration stage. This study can provide a non-destructive approach for durability design of marine concrete. From the relationship between electrical resistivity and chloride diffusivity, it is expected that the result is subsequently used as a calibration curve for an indirect control of the chloride diffusivity based on regular measurements of the electrical resistivity during concrete construction.

• Journal of Korean Society for Atmospheric Environment
• /
• v.26 no.6
• /
• pp.666-682
• /
• 2010

The forecasting system for Today's and Tomorrow's PM10 was developed based on the statistical model and the forecasting was performed at 9 AM to predict Today's 24 hour average PM10 concentration and at 5 PM to predict Tomorrow's 24 hour average PM10. The Today's forecasting model was operated based on measured air quality and meteorological data while Tomorrow's model was run by monitored data as well as the meteorological data calculated from the weather forecasting model such as MM5 (Mesoscale Meteorological Model version 5). The observed air quality data at ambient air quality monitoring stations as well as measured and forecasted meteorological data were reviewed to find the relationship with target PM10 concentrations by the regression analysis. The PM concentration, wind speed, precipitation rate, mixing height and dew-point deficit temperature were major variables to determine the level of PM10 and the wind direction at 500 hpa height was also a good indicator to identify the influence of long-range transport from other countries. The neural network, regression model, and decision tree method were used as the forecasting models to predict the class of a comprehensive air quality index and the final forecasting index was determined by the most frequent index among the three model's predicted indexes. The accuracy, false alarm rate, and probability of detection in Tomorrow's model were 72.4%, 0.0%, and 42.9% while those in Today's model were 80.8%, 12.5%, and 77.8%, respectively. The statistical model had the limitation to predict the rapid changing PM10 concentration by long-range transport from the outside of Korea and in this case the chemical transport model would be an alternative method.

• Fire Science and Engineering
• /
• v.24 no.3
• /
• pp.145-151
• /
• 2010

The fire in tunnel, when failed to extinguish at early stage, tends to easily develop to high temperature and spread to entire area of the tunnel because of considerable level of fire load and smoke control facility within the tunnel, resulting in severe damage to the people and tunnel structure. This study was intended to carry out the fire test with MHC fire curve, a scenario, which has the most rapid fire rise, on assumption of load ratio of 1, 20, 40, 60 and 70%, so as to identify the thermal characteristics of the concrete against spalling and the range of fire damage. The specimen was small scale sample as defined by EFNARC and the mixing ratio was based on 24 MPa, which is considered to be the normal strength. As a result of test, 16mm spalling was occurred on the lining under the non-load condition, while no spalling was occurred with 20% and 40% of load ratio. In case of 60% of load ratio, 24 mm of spalling was occurred and it failed in 10 minutes after heating in case of 70% load condition.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.24 no.4
• /
• pp.92-98
• /
• 1982

The major objective of this study was to investigate the heat resistance of epoxy resin mortar. For this purpose, these tests of compressive and bending strength were accomp- olished with various heating temperature (40˚C, 60˚C, 80˚C, 100˚C, 120˚C), and with various mixing ratio (1: 2, 1: 4, 1: 6, 1: 8, 1:10, 1:12, 1:14). The exprimental resin was to be Epi-Bis type epoxy resin, which is widely used as construction materials. The results obtained are summarized as follows; 1. The variations of color tone started to begin at 60˚C, and it has come out very heavy at 120˚C. It was assumed that the decrement of weight resulted from carbonization were about 0.22% at 100˚C, and about 0.34% at 120˚C. 2. The compressive and bending strength were increased with temperature rise up to 80˚C, but these were made rapid decrease when the given temperature was over. And so, the mean decrement of compressive and bending strength at 120˚C reached up to 35.5% and 26.4%, respectively. 3. The regression equation between compressive and bending strength for epoxy resin mortar under heat exposure were obtained as follows; od=0. 371oc+39. 23 (r=0. 986) And the estimated value of bending strength was corresponded to about 37 percent in comparing with that of the compressive strength. 4. Consquently, the heat resistance temperature of epoxy resin mortar was to be around 80˚C, and it was generally very low values. But it was regarded that the epoxy resin mortar will not be difficult with materials of civil engineering works and agricultural structures.

• Korean Journal of Materials Research
• /
• v.23 no.7
• /
• pp.353-358
• /
• 2013

To improve coating ability and the life of the coating, Ti based composite materials with hydroxyapatite(HA) should be developed. The raw materials of Ti-26wt%, Nb-1wt%, and Si with 10wt% HA were mixed for 24 h by a mixing machine and milled for 1 h to 6 h by planetary mechanical ball milling. Ti-26%Nb-1%Si-(10%HA) composites, composed of nontoxic elements, were fabricated successfully by spark plasma sintering(SPS) at $1000^{\circ}C$ under 70MPa. The relative density of the sintered Ti-Nb-Si-HA composites using the 24 h mixed powder, and the 6 h milled powder, was 91% and 97 %, respectively. The effects of HA contents and milling time on microstructure and mechanical properties were investigated by SEM and hardness tester, respectively. The Vickers hardness of the composites increased with increasing milling time and higher HA content. The Young's modulus of the sintered Ti-26%Nb-1%Si-10%HA composite using the 6 h-milled powder was 55.6 GPa, as obtained by compression test. Corrosion resistance of the Ti-26wt%Nb-1wt%Si composite was increased by milling and by the addition of 10wt%HA. Wear resistance was improved with increasing milling time. Biocompatibility of the Ti-Nb-Si alloys was improved by the addition of HA.

• Korean Journal of Materials Research
• /
• v.17 no.4
• /
• pp.207-214
• /
• 2007

We fabricated thermally-evaporated 10 -Ni/(poly)Si and 10 -Ni/1 -Ir/(poly)Si structures to investigate the microstructure of nickel monosilicide at the elevated temperatures required for annealing. Silicides underwent rapid at the temperatures of 300-1200 for 40 seconds. Silicides suitable for the salicide process formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester was used to investigate the sheet resistances. A transmission electron microscope(TEM) and an Auger depth profile scope were employed for the determination of vertical section structure and thickness. Nickel silicides with iridium on single crystal silicon actives and polycrystalline silicon gates shoed low resistance up to 1000 and 800, respectively, while the conventional nickle monosilicide showed low resistance below 700. Through TEM analysis, we confirmed that a uniform, 20 -thick silicide layer formed on the single-crystal silicon substrate for the Ir-inserted case while a non-uniform, agglomerated layer was observed for the conventional nickel silicide. On the polycrystalline silicon substrate, we confirmed that the conventional nickel silicide showed a unique silicon-silicide mixing at the high silicidation temperature of 1000. Auger depth profile analysis also supports the presence of thismixed microstructure. Our result implies that our newly proposed iridium-added NiSi process may widen the thermal process window for the salicide process and be suitable for nano-thick silicides.

• Ocean and Polar Research
• /
• v.29 no.4
• /
• pp.349-366
• /
• 2007

Seasonal variations of various physicochemical components (temperature, salinity, pH, DO, COD, DOC, nutrients-silicate, DIN, DIP) and potential limiting factor for phytoplankton primary production were studied in the surface water of semi-enclosed Masan Bay. Seasonal variations of nutrient concentrations, with lower values in summer and winter, and higher in fall, are probably controlled by freshwater loadings to the bay, benthic flux and magnitude of occurrence of phytoplankton communities. Their spatial distributional patterns are primarily dependent on physical mixing process between freshwater and coastal seawater, which result in a decreasing spatial gradient from inner to outer part of the bay. In the fall season of strong wave action, the major part of nutrient inputs (silicate, ammonium, dissolved inorganic phosphorus) comes from regeneration (benthic flux) at sediment-water interface. During the summer period, high Si:DIN and Si:DIP and low DIN:DIP relative to Redfield ratios suggest a N- and secondarily P-deficiency. During other seasons, however, silicate is the potential limiting factor for primary production, although the Si-deficiency is less pronounced in the outer region of the bay. Indeed, phytoplankton communities in Masan Bay are largely affected by the seasonal variability of limiting nutrients. On the other hand, the severe depletion of DIN (relatively higher silicate level) during summer with high freshwater discharge probably can be explained by N-uptake of temporary nanoflagellate blooms, which responds rapidly to pulsed nutrient loading events. In Masan Bay, this rapid nutrient consumption is considerably important as it can modify the phytoplankton community structures.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.4
• /
• pp.713-722
• /
• 2000

This study analysed error of measurement and reproducibility for particle size analysis by the laser diffraction spectrometer. Laser diffraction spectrometers has become a very important method of particle size analysis. This measuring method has the advantage of simple operation, good reproducibility and rapid analysis. A feeding and dispersing system have been developed, which allows mass throughputs between 0.1~23 g/min in flowing air and 1.4~35% in flowing liquid. It has been used as a feeder unit for wet and dry particle size analysis from diffraction patterns. Relevant parameters, such as particle shape, particle size, dispersion, flow rate, concentration were analysed for measuring error. And system parameters of instruments for measurement of dynamic processes, eg, measuring time, focal plane, injection pressure drop and dispersion effect by the ultrasonic and mixing of preliminary treatment, were also discussed.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.1
• /
• pp.163-170
• /
• 2007

To evaluate on the applicability of Chemical Compaction Pile (CCP) method to weak soil improvement, two kinds of testing chambers were fabricated and the changes of water content and shear stress associated with soil types, ages and distances from the center of pile were measured with different mixing proportions of CCP such as bottom ash, lime powder and added admixture. As results of test, it was noted that water content and shear stress of ground are mainly affected by the amount of lime powder and increase of the amount corresponds to rapid improvement of soil. And the improvement depended greatly on the types of soil also. It was finally found that CCP developed can be applicable to bearing pile as well as soil improvement since CCP has a bearing capacity enough to carry loads.