• Advances in concrete construction
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• v.8 no.4
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• pp.321-333
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• 2019

The present study targets to access the consequence of utilization of coarse aggregates retrieved from waste concrete as a substitution of coarse fraction of natural aggregates and silica nano-particles as partial substitution of cement using principles of factorial design. Furthermore, procedures of design of experiments are employed to examine the effect of use of recycled aggregates and nano-silica. In this investigation, compressive strength found after at 7, 28, 90 and 365 days, split and flexural tensile strength, ultrasonic pulse velocity and rebound number and are chosen as responses, whereas the percentages of recycled coarse aggregates (RCA%) and nano-silica (NS(%)) are selected as factors. Analysis of Variance has been conducted on the experimental results for the selected responses with consideration the both factors, which indicates that RCA (%) and NS (%) have substantial impact on the various responses. However, the present analysis depicts that interaction between factors has considerable effect on the chosen parameters of concrete. Furthermore, validation experiments are carried to validate these models for compressive and tensile strength for 100% RCA and 1% NS. The results of comparative study indicates that that the error of the estimation determined using the relevant models are found to be small (±5%) in comparison with the analogous experimental results, which authenticates the calculated models.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.11 no.1
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• pp.33-40
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• 2005

This study was carried out for effective utilization of recycling resources to investigate the repulping conditions of car air filter waste paper and to evaluate the application into corrugating medium papermaking by blending these repulped pulps. Car air filter waste paper was made of virgin BKP and it was dipped into phenol resin solution. It was well disintegrated by laboratory Valley beater with 10%(basis on oven-dried pulp weight) NaOH addition and defoamer usage. The optimal temperature, beating consistency and treatment time were mainly $40^{\circ}C$, 1% and $30{\sim}40$ minutes, respectively. Handsheets were prepared with various blending ratios between air filter recycled pulp and KOCC. In the case of $10{\sim}20%$ substitution with air filter recycled pulp, physical properties reductions as compressive strength and burst strength of sheets were lower than others. These results showed more favour than the partial substitution of KOCC for corrugating medium even though some strength reduction of paper. It was also observed that the waste water of air filter recycling was not affective to environmental problems.

• Journal of Electrochemical Science and Technology
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• v.12 no.4
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• pp.440-452
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• 2021

Enhancement of durability and reduction of maintenance cost of concrete, with the implementation of various approaches, has always been a matter of concern to researchers. The integration of pozzolans as a substitute for cement into the concrete is one of the most desirable technique. Silica fume (SF) and colloidal nanosilica (CS) have received a great deal of interest from researchers with their significant performance in improving the durability of concrete. The synergistic role of the micro and nano-silica particles in improving the main characteristics of cemented materials needs to be investigated. This work aims to examine the utility of partial substitution of cement by SF and CS in binary and ternary blends in the improvement of the durability characteristics linked to resistance for electrochemical corrosion using electrical resistivity and half-cell potential analysis and chloride penetration trough rapid chloride penetration test. Furthermore, the effects of this silica mixture on the compressive strength of concrete under normal and aggressive environment have also been investigated. Based on the maximum compression strength of the concrete, the optimal cement substituent ratios have been obtained as 12% SF and 1.5% CS for binary blends. The optimal CS and SF combination mixing ratios has been obtained as 1.0% and 12% respectively for ternary blends. The ternary blends with substitution of cement by optimal percentage of CS and SF exhibited decreased rate for electrochemical corrosion. The strength and durability studies were found in consistence with the microstructural analysis signifying the beneficiary role of CS and SF in upgrading the performance of concrete.

• Progress in Superconductivity
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• v.13 no.1
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• pp.12-17
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• 2011

We investigated the effects of Ba and Cu co-substitution on the structural and superconducting properties of ($Ru_{1-y}Cu_y$)($Sr_{1.67-x}Ba_xEu_{0.33}$)($Eu_{1.34}Ce_{0.66}$)$Cu_2O_z$ samples. X-ray diffraction(XRD) reveals that single-phase samples can be obtained in the range from x = 0.1 to 0.2 for ($Ru_{0.5}Cu_{0.5}$)($Sr_{1.67-x}Ba_xEu_{0.33}$)($Eu_{1.34}Ce_{0.66}$)$Cu_2O_z$ and from y = 0.25 to 0.5 for ($Ru_{1-y}Cu_y$)($Sr_{1.47}Ba_{0.2}Eu_{0.33}$)($Eu_{1.34}Ce_{0.66}$)$Cu_2O_z$, respectively. All samples with compositions of ($Ru_{0.5}Cu_{0.5}$)($Sr_{1.67-x}Ba_xEu_{0.33}$) ($Eu_{1.34}Ce_{0.66}$)$Cu_2O_z$ (x = 0 - 0.33) show superconducting transition behavior and the onset transition temperature decreases slightly with increasing x in consistent with the change of hole concentration estimated from room temperature thermoelectric power measurements. The XRD and resistivity measurements for the ($Ru_{1-y}Cu_y$)($Sr_{1.47}Ba_{0.2}Eu_{0.33}$)($Eu_{1.34}Ce_{0.66}$) $Cu_2O_z$ system indicate that the partial substitution of Cu for Ru is necessary to form phase pure samples, but result in a small change in transition temperature in the single-phase region from x = 0.25 to 0.5.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.1
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• pp.32-39
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• 2007

CO oxidation and selective CO oxidation of $La_xCe_{1-x}Co_yCu_{1-y}O_{3-{\alpha}}$ perovskite(x=1, 0.9, 0.7. 0.5; y=1, 0.9, 0.7, 0.5) were investigated. For CO oxidation, catalytic activities were studied according to different preparation conditions such as pH and calcination temperature. The influence of the change of the $O_2$ concentration for selective CO oxidation was studied, too. The substitution of Ce for La improved the catalytic activity for CO oxidation and selective CO oxidation and best activity was observed for $La_{0.7}Ce_{0.3}CoO_3$ prepared at pH 11 and calcined at $600^{\circ}C$. The temperature of 90% CO conversion for CO oxidation using $La_{0.7}Ce_{0.3}CoO_3$ was $230^{\circ}C$. In contrast to the enhancement effect by Ce substitution, the partial substitution of Cu for Co in $LaCo_yCu_{1-y}O_{3-{\alpha}}$ decreased catalytic activities for CO oxidation reaction compared to that using $LaCoO_3$. For selective CO oxidation, the best CO conversion was 66% at $230^{\circ}C$ for $La_{0.7}Ce_{0.3}CoO_3$. The CO conversion of $La_{0.7}Ce_{0.3}CoO_3$ was greatly increased from 66% to 91% as increasing $O_2$ concentration from 1% to 2%.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.407-414
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• 1999

We have studied the reduction of NO by CO over perovskite-type oxides prepared by malic and method. The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxides. In the $LaCoO_3$ type catalyst, the partial substitution of Sr into A site enhanced the catalytic activity on the conversion of NO at less than $350^{\circ}C$. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$ catalyst, the partial substitution of Fe or Mn into B site enhanced the conversion of NO, but excess amount of Fe decreased the conversion of NO. In addition, $La_{0.6}Sr_{0.4}Co_{0.8}Fe_{0.2}O_3$ mixed with $SnO_2$ or $MnO_2$ showed the synergy effect on the reduction of NO. The introduction of water into reactants feed decreased the catalytic activity but the deactivation was shown to be reversible. The introduction of $SO_2$ into reactants feed also decreased the catalytic activity.

• Journal of Life Science
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• v.14 no.6 s.67
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• pp.963-966
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• 2004

The sequence of ITS (partial 16S ribosomal DNA, complete ITS1, 5.8S ribosomal DNA and ITS2, and partial 28S ribosomal DNA) was analysed by PCR and autosequencing in Sarcodon aspratus. The ITS lenght of S. aspratus was 716 base pair. As this sequence compared with other reports on S. aspratus (ace No AF335110), the sequence variation based on nucleotide deletion and substitution was $1.8\%$. This nucleotide variation rate in same species was very higher than in other species. Also, the sequence varitation rates between this S. aspratus and S. imbricatus, and S. squamus were $8\%\;and\;10\%$, respectively. This results suggested that the high sequence variation of S. aspratus might be caused specific host and inhabitat environment which limited gene flow.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.19-25
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• 2010

Traditional Kr$\ddot{o}$ger-Vink (K-V) notation defines sites in ionic crystals as interstitial or belonging to host ions. It enables description and calculations of combinations of native and foreign defects, including dopants and substituents. However, some materials exhibit inherently disordered partial occupancy of ions and vacancies, or partial occupancy of two types of ions. For instance, the high temperature disordered phases of $Bi_2O_3$, $Ba_2In_2O_5$, $La_2Mo_2O_9$, mayenite $Ca_{12}Al_{14}O_{33}$, AgI, and $CsHSO_4$ are all good ionic conductors and thus obviously contain charged point defects. But traditional K-V notation cannot account for a charge compensating defect in each case, without resorting to terms like "100% substitution" or "Frenkel disorder". the former arbitrary and awkward and the latter inappropriate. Instead, a K-V compatible nomenclature in which the partially occupied site is defined as the perfect site, has been proposed. I here introduce it thoroughly and provide a number of examples.

• Electrical & Electronic Materials
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• v.7 no.1
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• pp.32-41
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• 1994

In this study, the TSC spectroscopy has been applied to investigate the influence of structural change due to a process of curing reaction on the electrical properties of epoxy composites cured with acid-anhydride. Five TSC peaks appeared in -160-250[.deg.C]: in the low temperature region below glass transition temperature(T$\_$g/), three relaxation mode peaks due to action of side chains, substitution group or terminal groups have been observed, a peak associated with T$\_$g/, appeared in 110[.deg. C] and p peak due to ionic space charges located in 150[.deg.C]. Each peak was separated into elementary peaks by the partial polarization procedure, and the distribution of activation energy and relaxation time were analized to clearify the origin of each peak. Also, overaboundantly added hardener separated a .betha. peak near 10[.deg. C] into two peaks of .betha.$\_$1/(10.deg. C) and .betha.$\_$2/(20.deg. C) according to increasement of forming field, and the separated hardener was oxidated thermally with increasing surrounding temperatures. The expansion of the free volume need in molecular motion and the reduction of the structural packing density through thermal oxidation process increased TSC between .alpha. peak and .betha. peak and decreased T$\_$g/.

• KCI Concrete Journal
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• v.11 no.3
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• pp.89-97
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• 1999

The purpose of this research is to investigate the utilization of recycled fine aggregates as a material to apply to a building finished walls or as a decorating material in combination with a polymer. The strengths of two resin mortars using recycled fine aggregates and natural fine aggregates was made. In order to improve the workability and the strength of the resin mortar with recycled fine aggregates, partial replacement of recycled fine aggregates with natural ones was made with the application of various type of fillers. The results, it show that the compressive strength and flexural strength of resin mortar using the recycled fine aggregates were about 70% to 100% of those of resin mortar using natural fine aggregates. It was enough to assure the utilization of the recycled fine aggregates as a material for the production of resin mortar. From the result of partial replacement of recycled fine aggregates with natural ones, the compressive strength was Increased from 5% to 15% and the flexural strength was much as 5% to 20% as a result of 70% substitution It was also found that the use of garnet powder shows a similar tendency in the compressive strength and slag powder does in the flexural strength and tensile strength.