• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.37-40
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• 2008

Many engineers find the way of improving the old building's structural behavior in the remodeling project which is performed using artificial openings for merging two houses. This test was performed to verify the characteristics of coupling beams according to the shape of the openings. One of test specimen has rectangle shape and the other was made by the circle shaped opening and one has coupling member only as slabs. Additionally, three specimens which have openings have 23% ratio in opening area to total wall area. Consequently, solid type which have no opening area shows shear failure. In the case of CW-RBS which have rectangular shaped opening, cracks are developed in coupling beam significantly. And CW-CS which has circular opening failed in shear showing development of diagonal cracks at wall toes and wall mid-height. It is thought that degradation of the wall strength is under the control of the opening shape and coupling beam-wall connection area.

• Journal of Hydrogen and New Energy
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• v.29 no.5
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• pp.473-482
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• 2018

To check applicability of recently developed new oxygen carrier for 0.5 MWth chemical looping combustion system, reactivity tests were carried out at high temperature and high pressure conditions. Pressure, temperature, gas velocity, $CH_4$ flow rate, and solid height were considered as operating variables. The new oxygen carrier (N016-R4) showed not only high fuel conversion but also high $CO_2$ selectivity within all the operating conditions in this study. The reactivity of N016-R4 particle was compared with previous oxygen carriers. The N016-R4 particle represented outstanding reactivity among 10 oxygen carriers in terms of fuel conversion and $CO_2$ selectivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.49-49
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• 2008

ZnO-based varistors have been widely used for voltage stabilization or transient surge suppression in electric power systems and electronic circuits. Recently, It has reported that the varistor behavior with nonlinear coefficient of 6~17 in Mn-doped ZnO. In this study we have chosen the composition of ZnO-$TeO_2-Mn_3O_4$ (ZTM) system to the purpose of whether varistor behavior appeared in doped ZnO by the solid state sintering or not. We investigated the sintering and electric properties of 0.5~3.0 at% Mn doped ZnO-1.0 at% $TeO_2$ system. Electrical properties, such as current-voltage (I-V), capacitance-voltage (C-V), and impedance spectroscopy were conducted. $TeO_2$ itself melts at $732^{\circ}C$ in air but forms the $ZnTeO_3$ phase with ZnO as increasing temperature and therefore retards the densification of ZnO to $1000^{\circ}C$. The average grain size of sintered samples was at about $3{\mu}m$ and decreased with increasing Mn contents. It was found that a good varistor characteristics were developed in ZTM system sintered at $1100^{\circ}C$ (nonlinear coefficient $\alpha$ ~ 60). The results of C-V characteristics such as barrier height ($\Theta$), donor density ($N_d$), depletion layer (W), and interface state density ($N_t$) in ZTM ceramics were $4\times10^{17}cm^{-3}$, 0.7 V, 40 nm, and $1.6\times10^{12}cm^{-2}$, respectively. It will be discussed about the stability and homogeneity of grain boundaries using distribution parameter ($\alpha$) simulated with the Z(T)"-logf plots in ZTM system.

• Advances in environmental research
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• v.3 no.3
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• pp.231-251
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• 2014

The present study examines the phosphate adsorption potential and behavior of mixture of Ground Burnt Patties (GBP), a solid waste generated from cooking fuel used in earthen stoves and Red Soil (RS), a natural substance in fixed bed column mode operation. The characterization of adsorbent was done by Proton Induced X-ray Emission (PIXE), and Proton Induced ${\gamma}$-ray Emission (PIGE) methods. The FTIR spectroscopy of spent adsorbent reveals the presence of absorbance peak at $1127cm^{-1}$ which appears due to P = O stretching, thus confirming phosphate adsorption. The effects of bed height (10, 15 and 20 cm), flow rate (2.5, 5 and 7.5 mL/min) and initial phosphate concentration (5 and 15 mg/L) on breakthrough curves were explored. Both the breakthrough and exhaustion time increased with increase in bed depth, decrease in flow rate and influent concentration. Thomas model, Yoon-Nelson model and Modified Dose Response model were used to fit the column adsorption data using nonlinear regression analysis while Bed Depth Service Time model followed linear regression analysis under different experimental condition to evaluate model parameters that are useful in scale up of the process. The values of correlation coefficient ($R^2$) and the Sum of Square Error (SSE) revealed the Modified Dose Response model as the best fitted model to the experimental data. The adsorbent mixture responded effectively to the desorption and reusability experiment. The results of this finding advocated that mixture of GBP and RS can be used as a low cost, highly efficient adsorbent for phosphate removal from aqueous solution.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.1
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• pp.93-101
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• 2011

The modeling of SDR was carried out for the application of the solid waste incineration system. To find optimum operating condition for removal of acidic gases, computation fluid dynamic(CFD) model was used. In this study, the temperature profile of SDR(spray dry reactor) and the gas velocity profile for different models were investigated. In this model, the diameter of SDR was 3 meter and the height of SDR was 9 meter. The amount of inlet combustion gas of SDR was $6,125Nm^3/hr$ and the inlet temperature of SDR was 493 K. The amount of lime injection of SDR was 151 kg/hr. When the inlet shape of SDR was changed, the temperatur of SDR was changed and the gas velocity of SDR was 0.48 m/sec to 1.17m/sec and the outlet gas velocity of SDR was 6.9 m/sec to 7.42m/sec As a result of modeling, the average velocities in SDR and outlet were 0.489 m/sec and 7.424 m/sec, respectively, in which the temperature of outlet in SDR was 448 K.

• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.595-609
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• 2022

Prestressed composite steel-concrete beams are still a technology restricted to repair sites of large-scale structures and spans. One of the reasons for that is the absence of standard frameworks and publications regarding their design and implementation. In addition, the primary normative codes do not address this subject directly, which might be related to a scarcity of papers indicating methods of design that would align the two technics, composite beams and external prestressing. In this context, this paper proposes methods to analyze the sizing of prestressed composite beams submitted to pre-tension and post-tension with a straight or polynomial layout cable. This inquiry inspected a hundred and twenty models of prestressed composite beams according to its prestressing technology and the eccentricity and value of the prestressing force. The evaluation also included the ratio between span and height of the steel profile, thickness and typology of the concrete slab, and layout of the prestressing cables. As for the results, it was observed that the eccentricity of the prestressing force doesn't significantly influence the bending resistance. In prestressed composite beams subjected to a sagging moment, the ratio L/d can reach 35 and 30 for steel-concrete composite slabs and solid concrete slabs, respectively. Considering the negative bending moment resistance, the value of the L/d ratio must be less than or equal to 25, regardless of the type of slab. When it comes to the value of the prestressing force, a variation greater than 10% causes a 2.6% increase in the positive bending moment resistance and a 4% decrease in the negative bending moment resistance. The pre-tensioned composite beams showed a superior response to flexural-compression and excessive compression limit states than the post-tensioned ones.

• Korean Journal of Food Science and Technology
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• v.10 no.4
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• pp.398-403
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• 1978

Squid was dried on the fluidized-bed in the drying chamber filled with solid particles which were also fluidized with hot-air, and effects of the fluidized particles, the squid's height from the grid and the drying temperature on the drying rate and quality of the squid were observed The mechanism of moisture transfer during the falling rate period was also derived. 1. Sodium chloride was found to be the most suitable fluidized particles and at an air velocity of 3.8 m/sec, optimal fluidization state of this particle was obtained. 2. Uniform profiles of temperature were obtained at a point 4 cm above the grid and the location of squid on the fluidized-bed observed to be suitable when it was 4 cm above the grid. 3. At an air velocity of 3.8 m/sec and when the location height of the squid on the fluidized-bed was 4 cm, the optimal temperature for the drying time which is required to reduce the moisture from 80.8% to 18-22% was 8.5 hours. 4. Drying data followed the empirical equation of unsteady state diffusion $log\;(\frac{W-We}{Wc-We})=-m{\theta}$ in the region of the moisture contents measured and the drying constant (m) was calculated as $0.32hr^{-1}$. These results suggested that the migration of moisture during the falling rate period is due to a diffusion type mechanism. 5. The short constant rate period was observed in the early stage and thereafter, drying was controlled by the falling rate period, and the time ratio of the fluidized bed drying to the through circulation drying for reducing the squid's moisture contents to the same level at the same drying temperature was 1 : 1.4 6. Comparisons of fluidized-bed dried squid and sun dried squid in sale showed that there was no significant change in qualities such as external appearance and hydrogen ion concentration of dry product.

• Journal of Animal Environmental Science
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• v.14 no.2
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• pp.119-128
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• 2008

This experiment was conducted to investigate the effects of concentrated pig slurry using membrane filter on growth of tomato in nutriculture. Pig slurry was filtered by ultra filtration and concentrated by reverse osmosis process. Filtration of pig slurry was necessary to prevent the hose clogging in nutriculture. The concentrated pig slurry (CS) and nutrient solution (NS) were mixed by six different mixing ratios of 0:100, 20:80, 40:60, 60:40%, 80: 20 and 100%:0% based on nitrogen content. The chemical nutrient solution was the solution of National Horticulture Research Station for the growth of tomato. The concentration of nutrient solution was adjusted a range of $1.6{\sim}2.0mS/cm$ in EC. The plant height of tomato treated with CS 20+NS 80% was similar with NS 100% control plot. Plant height was highest in the plot of CS 20+NS 80%. The treatment of 100% concentrated pig slurry was lowest in the gowth characteristics of tomato. Number of cluster was very lower in 100% concentrated pig slurry compared with plot of chemical nutrient solution. In the beginning of growth stage, SPAD reading value was reduced in plot treated with CS 100%, but CS 20+NS 80% plot was higher compared to 100% concentrated pig slurry. SPAD value of tomato leaves was decreased as the amount of CS was increased. The SPAD value also in treatment of concentrated pig slurry was lower in the middle growth stage compared to control plot. The dry weight of stem and leaf were 107.4, 104.2g in plot of NS 100% and CS 20%+NS 80%, respectively. The fruit number and weight were decreased at high application plots of concentrated pig slurry, The fruit setting of tomato showed lowest in the plot treated with 100% concentrated pig slurry, and the growth of tomato severely decreased after application of 100% CS treatment. In conclusion, the growth characteristics such as plant height and fruit weight of tomato were not significantly different between the plots treated with mixture of 20% CS +80%NS and 100% nutrient solution treatment. In conclusion, the mixture solution of 20% of concentrated pig slurry and 80% of nutrient solution could be used as a nutrition solution of tomato nuticulture.

• Journal of Korean Society of Forest Science
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• v.108 no.1
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• pp.29-39
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• 2019

The objective of this study was to suggest a suitable amount of fertilizer using the changes in growth performances and soil properties for improving survival and quality of Zelkova serrata trees in a harvested Pinus rigida plantation. One-year-old containerized seedlings of Z. serrata were planted with the density of 3000 seedlings $ha^{-1}$ in end of March 2011 at Gwangneung experimental forest, Pocheon. Solid compound fertilizer (N:P:K=3:4:1) were applied yearly in three amounts (control: no fertilization, F1: $180kg\;ha^{-1}$, and F2: $360kg\;ha^{-1}$) every May from 2011 to 2013. We analyzed soil properties before (2011) and after (2012 and 2017) fertilization. And we measured the root collar diameter and height of Z. serrata trees from 2011 to 2016, and then calculated H/D ratio and stem volume. Soil properties at Z. serrata plantation did not show difference according to fertilization level in every investigation year. As time passed after planting, however, concentrations of total nitrogen and available phosphorus were increased from decreased. The growth of root collar diameter, height and stem volume of Z. serrata trees at F2 plot were significantly higher those at the other plots after only 2 years of fertilization. Because Z. serrata tree demand to more nutrient during the early growing period. The survival rate of Z. serrata trees at control plot was significantly lower than that at the other plots. This might be due to Z. serrata trees at control plot had not the upper hand from competition with vegetation at the early in planting. However, the growth of height and stem volume of Z. serrata trees between F1 and F2 plots did not show difference over 6 years after planting. Consequently, we could suggest that Z. serrata trees need to F1 fertilization level for considering improving survival and quality of Z. serrata trees and economical efficiency of plantation managements after harvesting P. rigida plantation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.1 no.1
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• pp.53-68
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• 1981

Most clays under sustained load exhibit time-dependent deformation because of creep movement of soil particles and many investigators have attempted to relate their findings to the creep behavior of natural ground and to the long-term stability of slopes. Since the creep behavior of clays may assume a variety of forms depending on such factors as soil plasticity, activity and water content, it is difficult and complicated to analyse the creep behavior of clays. Rheological models composed of linear springs in combination with linear or nonlinear dashpots and sliders, are generally used for the mathematical description of the time-dependent behavior of soils. Most rheological models, however, have been proposed to simulate the behavior of secondary compression for saturated clays and few definitive data exist that can evaluate the behavior of non-saturated clays under the action of sustained stress. The clays change gradually from a solid state through plastic state to a liquid state with increasing water content, therefore, the rheological models also change. On the other hand, creep is time-dependent, and also the effect of thixotropy is time-function. Consequently, there may be certain correlations between creep behavior and the effects of thixotropy in compacted clays. In addition, the states of clay depend on water content and hence the height of the specimen under drained conditions. Futhermore, based on present and past studies, because immediate elastic deformation occurs instantly after the pressure increment without time-delayed behavior, the factor representing immediate elastic deformations in the rheological model is necessary. The investigation described in this paper, based on rheological model, is designed to identify the immediate elastic deformations and the effects of thixotropy and height of clay specimens with varing water content and stress level on creep deformations. For these purposes, the uniaxial drain-type creep tests were performed. Test results and data for three compacted clays have shown that a linear top spring is needed to account for immediate elastic deformations in the rheological model, and at lower water content below the visco-plastic limit, the effects of thixotropy and height of clay specimens can be represented by the proposed rheological model not considering the effects. Therefore, the rheological model does not necessitate the other factors representing these effects. On the other hand, at water content higher than the visco-plastic limit, although the state behavior of clays is visco-plastic or viscous flow at the beginning of the test, the state behavior, in the case of the lower height sample, does not represent the same behavior during the process of the test, because of rapid drainage. In these cases, the rheological model does not coincide with the model in the case of the higher specimens.