• Structural Engineering and Mechanics
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• v.63 no.1
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• pp.55-64
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• 2017

The paper concerns concrete carbonation, the phenomena that occurs in every type of climate, especially in urban-industrial areas. In European Standards, including Eurocode (EC) for concrete structures the demanded durability of construction located in the conditions of the carbonation threat is mainly assured by the selection of suitable thickness of reinforcement cover. According to EC0 and EC2, the thickness of the cover in the particular class of exposure depends on the structural class/category and concrete compressive strength class which is determined by cement content and water-cement ratio (thus the quantitative composition) but it is not differentiated for various cements, nor additives (i.e., qualitative composition), nor technological types of concrete. As a consequence the selected thickness of concrete cover is in fact a far estimation - sometimes too exaggerated (too safe or too risky). The paper presents the elaborated "self-terminated carbonation model" that includes abovementioned factors and enables to indicate the maximal possible depth of carbonation. This is possible because presented model is a hyperbolic function of carbonation depth in time (the other models published in the literature use the parabolic function that theoretically assume the infinite increase of carbonation depth value). The paper discusses the presented model in comparison to other models published in the literature, moreover it contains the algorithm of concrete cover design with use of the model as well as an example of calculation of the cover thickness.

• Journal of Microbiology and Biotechnology
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• v.23 no.4
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• pp.539-544
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• 2013

The effects of culture depth (2-10 cm) and cell density on the growth rate and biomass productivity of Chlorella sp. XQ-200419 were investigated through the use of a self-designed open circular pond photobioreactor-imitation system. With increases in culture depths from 2 to 10 cm, the growth rate decreased significantly from 1.08 /d to 0.39 /d. However, the biomass productivity only increased slightly from 8.41 to 11.22 $g/m^2/d$. The biomass productivity (11.08 $g/m^2/d$) achieved in 4 cm culture with an initial $OD_{540}$ of 0.95 was similar to that achieved in 10 cm culture with an initial $OD_{540}$ of 0.5. In addition, the duration of maximal areal productivity at a 4 cm depth was prolonged from 1 to 4 days, a finding that was also similar to that of the culture at a 10 cm depth. In both cases, the initial areal biomass densities were identical. Based on these results and previous studies, it can be concluded that the influence of culture depth and cell density on areal biomass productivity is actually due to different areal biomass densities. Under suitable conditions, there are a range of optimal biomass densities, and areal biomass productivity reaches its maximum when the biomass density is within these optimal ranges. Otherwise, biomass productivity will decrease. Therefore, a key factor for high biomass productivity is to maintain an optimal biomass density.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.2
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• pp.117-127
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• 1996

In this paper, we present the bit error performances of 4PSK and 8PSK signal transmission schemes using Maximal Ratio Combining diversity reception for m-distribution and Rician fading channels. The suitability of modeling a Rician fading environment by a properly chosen m-distribution model is examined. Using the error performance of the derived equation has been evaluated and shown in figures as a function of fading index (m), Rician factor (K), diversity branches number (L) and E($E_b/N_o$). It is found that MRC (Maximal Ratio Combining) diversity technique is very efficient for reducing the effects of fading, And then, diversity benifit much large as depth of fading becomes deeper but more decreases as many diversity branchs. Also the results show that the error performance corresponds as much as fading becomes weak and increases with the number diversty branches.

• The Korean Journal of Physiology
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• v.5 no.2
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• pp.15-27
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• 1971

Physiological analysis of the physical exercise was made on 9 subjects performing mountain climbing. The course between two points (256 and 516 meters altitude) was 1,300 meters in distance and difference of vertical height was 260 meters making the mean grade of 20%. In the field, the heart rates during uphill or downhill walk were recorded by EKG radio-telemetry. In the laboratory, oxygen consumption was obtained by the recorded heart rates, using individual heart rate vs oxygen consumption diagram obtained by treadmill test. the following results were obtained. 1. Uphill walk time was 36.5 minutes, and during this period the mean heart rate was 149.0 heats/min and peak heart rate was 169.2 beats/min. The total heart beats during the uphill walk was 5.433 beats. 2. The ratio of individual mean heart rate during the uphill walk to the maximal heart rate distributed between 66.6% and 98.3%, and the mean of the total group was 83.1%. The ratio of peak heart rate of uphill walk to the maximal heart rate was 94.5% in the group. Thus uphill walk of a 20% grade mountain course was an exhaustive exercise. 3. Oxygen consumption during uphill walk was 2.22 l/min (ranged between 1.79 and 2.70 l/min) and the ratio of this to the resting oxygen consumption was 8.31. The peak value of oxygen consumption during uphill walk was 2.73 l/min and the ratio of this to the resting oxygen consumption was 10.39. 4. Energy expenditure during uphill walk showed a mean of 11.1 kcal/min and the peak expenditure rate was 13.6 kcal/min. The total energy expenditure during 36.5 minutes of uphill walk was 396 kcal. 5. In downhill walk, the time was 31.7 minutes, mean heart rate was 118.4 (ranged between 100.1 and 142.7) beats/min, and the peak heart rate was only 129.4 beats/min. The ratio of mean heart rate to the maximal heart rate was 66.3%. Total heart beats during downhill walk was 3,710 beats. The ratio of downhill oxygen consumption to the resting consumption was 5.70. The rate of energy expenditure was 7.5 kcal/min, and the total onery expenditure during the 31.7 minutes of downhill walk was 228 kcal. 6. The effect of training was manifest in the uphill walk and not in the downhill walk. After training in mountain course walk, i) the uphill time was shortened, ii) mean heart rate increased, iii) time vs heart rate curve became smooth and showed less frequent zig-zag, i.e., the depth of trough on the curve decreased and the magnitude was less than 10 beats. In non-trained subject the depth of trough on the curve was greater than 50 beats and appeared more frequently. 7. Mountain climbing is a good health promotion exercise. For the promotion of health the reasonable amount of uphill mountain walk exercise in a 20% grade course is a walk for 40 or 50 minutes duration once a week.

• Restorative Dentistry and Endodontics
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• v.19 no.1
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• pp.231-254
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• 1994

Fracture of cusp, on posterior teeth, especially those carious or restored, is major cause of tooth loss. Inappropriate treatments, such as unnecessarily wide cavity preparations, increase the potential of further trauma and possible fracture of the remaining tooth structures. Fracture potential may be directly related to the stresses exerted upon the tooth during masticatory function. The purpose of this study is to evaluate the fracture resistance of tooth, restored with composite resin inlay. In this study, MOD inlay cavity prepared on maxillary first premolar and restored with composite resin inlay. Three dimensional finite element models with eight nodes isoparametric solid element, developed by serial grinding-photographing technique. These models have various occlusal isthmus and depth of cavity, 1/2, 1/3 and 1/4 of isthmus width and 0.7, 0.85 and 1.0 of depth of cavity. The magnitude of load was 474 N and 172 N as presented to maximal biting force and normal chewing force. These loads applied onto ridges of buccal and lingual cusp. These models analyzed with three dimensional finite element method. The results of this study were as follows : 1. There is no difference of displacement between width of occlusal isthmus and depth of cavity. 2. The stress concentrated at bucco-mesial comer, bucco-disal comer, pulpal line angle and the interface area between internal slopes of cusp and resin inlay. 3. The vector of stress direct to buccal and lingual side from center of cavity, to tooth surface going on to enamel. The magnitude of vector increase from occlusal surface to cervix. 4. The crack of tooth start interface area, between internal slop of buccal cusp and resin inlay. It progresses through buccopulpal line angle to cervix at buccomesial and buccodistal comer. 5. The influence with depth of cavity to fracture of tooth was more than width of isthmus. 6. It would be favorable to make the isthmus width narrower than a third of the intercuspal distance and depth of cavity is below 1 : 0.7.

• Korean Journal of Environment and Ecology
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• v.30 no.3
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• pp.308-319
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• 2016

The purpose of this study is to identify distribution patterns of hydrophytes in the Mokpo wetland in relation to the depth of water. Sample surveys were conducted based on plant species distribution status and water depths at 274 spots. This study also developed a detailed depth distribution map for Mokpo wetland, which was never done in any previous studies. Through this study, it was found that the average depth of the wetland was 77cm (${\pm}29cm$) and the maximal depth was 157cm. The outer edge was no deeper than 60cm and the center approximately 120~130cm in depth, forming a concave bowl-like shape. This research confirmed inhabitation of 6 types of submerged plants (Verticillate hydrilla, Vallisneria natans, Najas graminea, Potamogeton cripus, Ceratophyllum demersum, and Potamogeton brechtoldi), and three types of floating leaved plants (Euryale ferox, Hydrocharis dubia and Trapa japonica) in the surveyed areas of the wetland. The distribution of these hydrophytes showed a statistically significant difference (${\chi}^2=982.2$, df = 8, p < 0.01), which confirms the fact that distribution varies based on environmental conditions. The most frequently observed species was Trapa japonicas at 244 times, and it showed a distribution pattern by which coverage increased with greater depth, as was also seen in the case of Potamogeton cripus. Five species-Euryale ferox, Hydrocharis dubid, Verticillate hydrilla, Najas graminea, and Ceratophyllum demersum-showed a negative correlation to depth, by which coverage decreased with increasing depth. It has been shown that fundamentally, the distribution of hydrophytes based on depth is affected by ecological factors, but also reflects the environmental properties of Mokpo wetland.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.1
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• pp.77-88
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• 2011

This study was carried out to investigate the effects of soil depth and planting density on the growth of lettuce, crown daisy, and strawberry on a rooftop condition using artificial soil as a growth media. The vegetable crops showed better growth for plant height (cm), plant width (cm), plant fresh weight (g), and Fo, Fm and Fv/m on 20cm depth soil than 10cm depth soil except strawberry. Planting density of $16/m^2$ and $64/m^2$ did not show significant differences on the growth of the crops. Soil moisture content and EC were low for 10cm depth soil in lettuce plots, whereas there was no significant differences on soil moisture and EC between two soil depth in strawberry plots. Hunter's L, a, and b values showed the leaf color of lettuce dark green on 20cm depth soil and reddish on 10cm depth soil. Results showed that soil depth suitable for crop growth on rooftop conditions was 20cm rather than 10cm. Growth response of the crops showed no significant difference between $16/m^2$ and $64/m^2$, indicating that planting density of 64 $plants/m^2$ could be practiced on rooftop conditions. Lettuce growth rapidly changed in control treatment in which leaves were not pinched out, while slowly changed in plants which leaves were periodically pinched out. In the case of control plot, it was impossible to harvest because withering of lower leaves after blossom on June 22. The plant of crown daisy in which pinching was not conducted, blossomed on June 7, and the plants were removed since its aesthetical value was lost. Strawberry seemed to be a suitable vegetable crop for rooftop conditions based on its high covering rate and extended growth period until late October. The soil depth 20cm and planting density 64 $plants/m^2$ were suitable for vegetable crops on green roof system using artificial soil.

• Journal of Periodontal and Implant Science
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• v.30 no.2
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• pp.429-442
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• 2000

Based on current evidence in the literature, it is known that endotoxin is a weakly adherent surface phenomenon and that power-driven instruments can be used to accomplish definitive root detoxification and maximal wound healing without overinstrumentation of root and without extensive cementum removal. And one of the newly developed curette tips used with low power of piezoelectric ultrasonic scaler, is effective to remove calculus and not to remove the excessive cementum. The purpose of this study is therefore, to assess the influence of ultrasonic power and various working parameters on root substitute removal when instrumentation is performed with the curette tip on piezoelectric ultrasonic scaler. This study assessed defect depth, width and area resulting from instrumentation using a piezoelectric ultrasonic scaler with a curette type tip in vitro to acrylic resin block as a root substitute. The working parameters was standardized by the sledge device which controls lateral force(0.5 N, 1 N, 2 N) and instrumentation time(5 sec, 10 sec, 20 sec) and power setting was adjusted 0,2,4,8 in P mode. Power setting had the greatest influence on defect depth compared to lateral force and instrumentation time(standardized regression parameter estimates${\pm}$standard error, $0.37{\pm}0.02$, $0.19{\pm}0.02$, $0.07{\pm}0.02$). The effects on defect area also greatest for power setting($0.57{\pm}0.03$) compared to lateral force and instrumentation time($0.33{\pm}0.03$, $0.12{\pm}0.03$). The effect of the power setting on the defect width($0.15{\pm}0.01$) is not so great as defect depth or defect area compared to lateral force($0.12{\pm}0.01$) and effect of instrumentation time is minimal($0.02{\pm}0.01$). It could be concluded that the power setting has the greatest influence on the defect depth and area in curette type tip with low power of piezoelectric ultrasonic device. Many parameters can be adjusted in various situation in clinical use of piezoelectric ultrasonic scaler but the power setting is the first parameter to be adjusted.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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• pp.48-56
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• 2009

In this paper, laser-assisted machining(LAM) has been employed to machine hot isostatically pressed (HIPed) Si3N4 work pieces. Due to little residual flaws and porosity, HIPed $Si_3N_4$ work pieces are more difficult to machine compared to normally sintered $Si_3N_4$ workpieces. In LAM, the intense energy of laser was used to enhance machinability by locally heating the workpiece and thus reducing yield strength. In experiments, the laser power ranges from 200W to 800W and the diameter of work pieces is 16mm. While machining, the surface temperature was kept nearly constant by laser heating except for a short period of rise time of max. 58 seconds. Results showed as feed rate increases the surface temperature of $Si_3N_4$ workpieces decreases slightly, whereas the effect of depth of cut is disregardable. With a laser power of 800W, achievable maximal depth of cut as 0.7mm and feed rate was 0.03mm/rev.

• Journal of KIISE:Software and Applications
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• v.36 no.11
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• pp.947-954
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• 2009

This paper proposes a novel method that reconstructs a surfel-based object by using visual hull from multiple images. The surfel is a point primitive that effectively approximates point-set surface. We create the surfel representation of an object from images by combining the LDC(Layered Depth Cube) surfel sampling with the concept of visual hull that represents the approximated shape from input images. Because the surfel representation requires relatively smaller memory resources than the polygonal one and its LDC resolution is freely changed, we can control the reconstruction quality of the target object and acquire the maximal quality on the given memory resource.