• Geomechanics and Engineering
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• v.16 no.2
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• pp.113-124
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• 2018

Under repeated loading, the residual stresses within the subgrade and subsoil can accelerate the deformation of the road structures. In this paper, a series of laboratory cyclic loading model tests and small-scale model tests were conducted to investigate the dynamic stress response within soils under different loading conditions. The experimental results showed that a dynamic stress accumulation effect occurred if the soil showed cumulative deformation: (1) the residual stress increased and accumulated with an increasing number of loading cycles, and (2) the residual stress was superimposed on the stress response of the subsequent loading cycles, inducing a greater peak stress response. There are two conditions that must be met for the dynamic stress accumulation effect to occur. A threshold state exists only if the external load exceeds the cyclic threshold stress. Then, the stress accumulation effect occurs. A higher loading frequency results in a higher rate of increase for the residual stress. In addition to the superposition of the increasing residual stress, soil densification might contribute to the increasing peak stress during cyclic loading. An increase in soil stiffness and a decrease in dissipative energy induce a greater stress transmission within the material.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.175-176
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• 2000

Electric fields and the wall voltages in a surface-type AC PDP cell were measured using a Laser Induced Fluorescence Spectroscopy. For the condition of He 100Torr, 200V sustain voltage and 50kHz sustain frequency, the wall voltage dropped from about 50V to about -75V within $1{\mu}sec$ after the main discharge. And the wall voltage decreased with the rate of $10.8V/{\mu}sec$ due to the accumulation of the space charges after $1{\mu}sec$. But when the operating pressure was 40Torr, it increased with the rate of $4.5V/{\mu}sec$ because the diffusion effect of the wall charge on MgO surface was more dominant than the accumulation effect of the space charges. During the pulse-off period, the wall voltage decreased slightly due to the diffusion of the wall charge. When the sustain voltage was 250V, the self-erasing discharge occurred, and the absolute value of the wall voltage decreased rapidly just after the pulses were off, which was caused by the accumulation of the charges generated by the self-erasing discharge.

• Journal of Technology Innovation
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• v.9 no.2
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• pp.56-76
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• 2001

The main purpose of this study is to analyse the digital divide and th determinants of ICT diffusion rate in Korean industries. We estimate the ICT diffusion function using the pooling data for this analysis. The results are as follows. First, the ICT capital accumulated in machinery & equipment, electrical machinery and construction industry is estimated to be 83% of total In capital stock in the 90s. Second, using the panel analysis, we find positive correlation among ICT diffusion, network effect and accumulation of human capital, which is more prominent in the service sector. Third, the estimation results show that the additional 1% increase of human capital accumulation will allow to increase the 0.69% of ICT capital intensity in Korean industries.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.1
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• pp.33-41
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• 1997

An attempt was made to enhance anaerobic treatment efficiency by adopting the anaerobic sequencing batch reactor(ASBR) process at a thermophilic temperature. Operational characteristics of the ASBR process were studied using laboratory scale reactors and concentrated organic wastewater composed of soluble starch and essential nutrients. Effects of fill to react ratio (F/R) were examined in the Phase I experiment, where the equivalent hydraulic retention time(HRT) was maintained at 5 days with the influent COD of 10g/L. A continuous stirred tank reactor(CSTR) was operated in parallel as a reference. Treatment efficiency was higher for the ASBRs because of continuous accumulation of volatile suspended solids(VSS) compared to the CSTR. However, the rate of gas production and organic removal per unit VSS in the ASBRs was much lower than the CSTR. This was caused by reduced methane fermentation due to accumulation of volatile acids(VA), especially for the case of low F/R, during the fill period. When the F/R was high, maximum VA was low and the VA decreased in short period. Consequently, more stable operation was possible with higher F/R. Effects of hydraulic loading rate on the efficiency was studied in the Phase II experiment, where the organic loading rate was elevated to 3333mg/L-d with the F/R of 0.12. Reduction of organic removal along with rapid increase of VA was observed and the stability of reaction was seriously impaired, when the influent COD was doubled. However, operation of the ASBR was quite stable, when the hydraulic loading rate was doubled and a cycle time was adjusted to 12 hour. It is essential to avoid rapid accumulation of VA during the fill period in order to maintain operational stability of the ASBR.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.7
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• pp.9-16
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• 1999

We have investigated effects of local damage accumulation for ultra-low energy As and B ion implant using highly efficient molecular dynamics(MD) scheme. We simulated ion implantation by MD simulation using recoil ion approximation (RIA) method and local cell damage accumulation (LCDA) model proposed in the paper. Local damage accumulation probability function consisted of deposited energy in a unit cell, implant dose rate, target material, projectile atom, and recoil event number. The simulated results were good agreement with the experimental and other simulated results. The MDRANGE results without damage accumulation were different from SIMS data in the tail region. We also simulated 2 dimensional dopant and damage profiles using the local damage accumulation model and recoil ion approximation method.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.2
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• pp.105-118
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• 2015

This study was carried out to investigate the effects of profile disturbance with different artificial accumulation history on physico-chemical properties of soil under plastic film house. The investigations included soil profile description using soil column cylinder auger F10cm x h110cm, in situ and laboratory measurements of soil properties at five sites each at the cucumber (Site Ic ~ Vc) and grape (Site Ig ~ Vg) plastic film houses with artificial soil accumulation. The sites except sites Ic, IVc, IVg and Vg, belong to ex-paddy area. The types of accumulates around root zone included sandy loam soil for 3 sites, loam soil for 1 site, saprolite for 2 sites, and multi-layer with different accumulates for 3 sites. Especially, Site IIg has mixed plow zone (Ap horizon) with original soil and saprolite, whereas disturbed soil layers of the other sites are composed of only external accumulates. The soil depth disturbed by artificial accumulation ranged from 20 cm, for Site IIg, to whole measured depth of 110 cm, for Site IVc, Vc, and Site IVg. Elapsed time from artificially accumulation to investigation time ranged from 3 months, Site IIc, to more than 20 years, Site Vg, paddy-soil covering over well-drained upland soil during land leveling in 1980s. Disturbed top layer in all sites except Site Vg had no structure, indicating low structural stability. In situ infiltration rate had no correlation with texture or organic matter content, but highest value with highest variability in Site IIIc, the shortest elapsed time since sandy loam soil accumulation. Relatively low infiltration rate was observed in sites accumulated by saprolite with coarse texture, presumably because its low structural stability in the way of weathering process could result in relatively high compaction in agro-machine work or irrigation. In all cucumber sites, there were water-transport limited zone with very low permeable or impermeability within 50 cm under soil surface, but Site IIg, IIIg, and Vg, with relatively weak disturbance or structured soil, were the reverse. We observed the big change in texture and re-increase of organic matter content, available phosphate, and exchangeable cations between disturbed layer and original soil layer. This study, therefore, suggest that the accumulation of coarse material such as saprolite for cultivating cash crop under plastic film house might not improve soil drainage and structural stability, inversely showing weaker disturbance of original soil profile with higher drainage.

• Journal of Environmental Health Sciences
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• v.22 no.3
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• pp.56-63
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• 1996

The results of the water purification studies using water parsley (Oenanthe javanica) were obtained as follows. The removal rate of nutrient salts increased with longer plant growth periods. The results of this study use the assumption, log(T+1) = $K(C_0-C)^A$, based on Prakish's Theory. The initial concentration was calculated from experimental data. A and K are closely related to the initial concentration. It is possible to model the concentration of residual salts, as time goes by, if concentration is constant. It was observed that water parsley neutralizes acid and alkali substances promptly. The maximum suitable neutralization period is 48 hours. But water parsley withered up in strong acid and alkali solutions within a week. The removal efficiency of Cd progresses in 2 steps, which are unrelated to the initial concentration of Cd. The first part of the curve shows the concentration rapid rate of Cd removal, followed by a levelling off. The removal rate of $NO_x-N$ in the sample water tank containing 0.5 ppm Cd was between 50~80% but the removal rate was less than 20% for the higher concentration. On the other hand, increased amounts of $PO_4-P$ in the sample water tank from the third day on suspected that $PO_4-P$ was desorbed from the water parsley. The accumulation efficiency of Cd in plant was increased in proportion to the initial concentration of Cd. The accumulation phenomenon was observed in the tanks more than 50~100 times.

• Journal of Nutrition and Health
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• v.30 no.3
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• pp.318-325
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• 1997

The purpose of this study was to investigate the effect of selenium supplementation of iron accumulation of rats fed diets containing high levels or iron. Sixty male Sprague-Dawley weaning rats were fed with diets containing various levels of iron(adequate : 35ppm, 2-fold : 70ppm, 4-fold : 140ppm) and selenium(adequat : 0.05ppm and high : 0.05ppm) for 12 weeks. Feed intakes of 2-fold and 4-fold iron groups were higher than that of adequate iron group. There was no difference body weight gain across iron and selenium containing diet groups. Hemoglobin level was increasd with iron increment and decreased with selenium supplementation. Iron contents in serum and tissues were increased as iron intake was increased. Liver iron content was decreased with selenium supplementation. Selenium content in liver was decreased with iron increment and increased with selenium supplementation. In the case of iron balance, iron excretion through urine and feces was significantly increased as iron intake was increased. However, apparent absorbability and retention rate of iron were not significantly affected by dietary iron or selenium.

• Asian Journal of Turfgrass Science
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• v.4 no.2
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• pp.125-131
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• 1990

This experiment was carried out in drder to study the changes of morphological characters and thatch weight on N-level and survey times N-levels were 0, 21, 28, 35, 42 and 49 g/m$^2$), respectively. The results are as follows. 1. Thatch weight was significantly different among survey times, and the interaction of survey time N-level. 2. The growth of Zoysia grass and thatch accumulation were incresed by higher N~level The highest value was obtained in all survey times. 3. Most survey characters and thatch accumulation was decreased by growth progressed. 4. Thatch increase rate(TIR) was the lowest at 28g Nm$^2$and T2-T3 period. 5. TIR was the positive significant correlated(P<0.05) with N-level, root weight, clipping weight and thatch weight.

• Journal of radiological science and technology
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• v.17 no.1
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• pp.77-86
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• 1994

The bone scan reflects the metabolic reaction of bone to a disease process, whether neoplastic, traumatic or inflammatory. In normal bone tissue, the labeled diphosphate complexes accumulate in the perivascular fluid next to the marrow cavity at the interface between uncalcified and calcified bone matrix. HMDP has the most rapid plasma clearance among the commonly used diphosphonate followed by MDP and then HEDP. I have studied about bone scan time by use of $^{99m}Tc-MDP$, and got 336 images from 112 patients. The result obtained as follow; 1. Accumulation rate of $^{99m}Tc-MDP$ is higher than other age groups in below 30-year old group. 2. Accumulation rate, in 10year old group, is 75.85% on 120min. but other groups are most high on 180 min. 3. The density differants between bone and soft tissue increased with time. 4. Image contrast is good in younger group than old.