• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.269-275
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• 2005

We analyzed the unit cell performance against the cathode porosity, which is supposed to be closely related with active sites for the cathode reaction. In order to fabricate the unit cells with different porosity in the cathode layer we changed the mixing ratio of fine and coarse LSCF cathode powders. The final porosity of each cathode layer was 14, 23, 27, $39\%$ respectively. According to the electrochemical analysis of unit cell performance via DC current interruption and AC impedance method, the electrodic polarization resistance was diminished as the cathode porosity increased. The decrease of polarization resistance was attributed due to the increase of active reaction sites and the enhancement of overall unit cell performance could be explained in the same line.

• Journal of the Korean GEO-environmental Society
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• v.15 no.11
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• pp.53-59
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• 2014

It has been generally recognized that the conventional rockfall protection nets have several problems to actual field application in the aspect of shock absorption, lack of pullout bearing capacities, and net damages. Because of the recognition, authors have tried to develop a new rockfall protection system consisted of shock absorption parts and hexagonal net configuration. In the previous research by the authors, the performance of the newly developed rockfall protection system has been investigated through the laboratory tests and the full-scale testing. In this study, subsequently, numerical analysis program is organized to make a confirmation of the structural stability and performance. For the correct design procedure of the hexagonal net system, it is essential to understand the various mechanical behavior of the entire system. It is also important to be reproduced the systematic characteristics of the system acquired by laboratory and full-scale testing by numerical analysis in order to carry out the numerical experiment to understand various mechanical behavior of the system. As a conclusion, the hexagonal net has better performance in mechanical and physical behavior compared with that of the rectangular net. Furthermore, due to the hexagonal net shows a good performance in aspect of the load distribution, it gives a good alternative in long-term management of the rockfall protection net.

• Korean Journal of Construction Engineering and Management
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• v.12 no.5
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• pp.71-80
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• 2011

Flying net should be installed on every 3 or 4 construction floor from 8m above ground according to the rule. In the apartment housing construction, flying net installation work has been recognized the most dangerous work among the whole works because a small mistake of labors might make their death accident. Sub-contractors specialized in flying net have been developing various flying net types. However, most works of installing flying net as working with the developed system are performed outside the apartment housing, so that the risk of fall in works of installing supports and unfolding net is still high. Furthermore, as using the previously developed flying net labors might bump into the frame or the wire rope for supporting so that it makes secondary accidents. The objective of this research is to produce the proto-type of anti-collision flying net system based on the result of problem analysis on the installation and detachment process and suggest the improved anti-collision flying net system, which is able to improve safety and field applicability by conducting field experiment and analyzing performance.

• Applied Chemistry for Engineering
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• v.31 no.4
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• pp.368-376
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• 2020

In this study, an analysis on the reaction characteristics of a catalyst using platinum (Pt) as an active oxidation metal catalyst for controlling SO₂ was performed. Pt/TiO₂ catalyst was prepared by using Pt as various precursor forms on a titania (TiO₂) support, and used for the experiment. There was no difference in performance of SO₂ oxidation according to Pt valence states such as Pt²⁺ or Pt⁴⁺ on Pt/TiO₂, and Pt chloride species such as PtCl_x reduces SO₂ oxidation performance. In addition, as a result of analyzing the valence state of the catalyst before and after the SO₂ oxidation reaction by XPS analysis, a decrease in lattice oxygen and an increase in surface chemisorbed oxygen after the SO₂ oxidation reaction were confirmed. Therefore it can be suggested that the oxidation reaction of SO₂ when using the Pt/TiO₂ catalyst is the major one following the Mar-Van Krevelen mechanism where the reaction of lattice oxygen corresponding to PtOx and the oxidation-reduction reaction by oxygen vacancy occur. Overall, it can be confirmed that the oxygen species of PtOx (Pt²⁺ or Pt⁴⁺) present on the catalyst acts as a major active site.

• Journal of the Korean GEO-environmental Society
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• v.15 no.9
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• pp.69-75
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• 2014

Rock fall protection system installed against rock slope is one of the most conventional way to protect nearby infra structures. Despite of wide application of typical rectangular nets, virtually installed to protect rock slope face, several problems have also been pointed out up to date. Rectangular draped nets are vulnerable to a sudden external shock such as rock fall, because it doesn't have any systematical buffers or shock absorbers. Furthermore, it has been widely recognized from the some cases of rock fall accident in Korea that rock fall protection nets cause wide range of failure in the rock slope faces due to insufficient pullout bearing capacity of fixing parts. Therefore, in this study, we tried to make a consideration about the problems of existing standard rock fall protection nets in Korea, and develop a new type of hexagonal net with a shock absorber based on design rock fall energy. In this paper, laboratory and full scale test procedure is described to analysis the performance of newly developed hexagonal rock fall net, and the key results are presented and discussed.

• Korean Journal of Cognitive Science
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• v.4 no.1
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• pp.213-242
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• 1993

During the past decades,several automatic indexing systems have been developed such as single term indexing.phrase indexing and thesaurus basedidndexing systems.Among these systems,single term indexing has been known as superior to others despte its simpicity of extracting meaningful terms.On the other hand,thesaurus based one has been conceived as producing low retrival rate ,mainly because thesauri do not usually have enough index terms.so that much of text data fail to be indexed if they do not match with any of index terms in thesauri.This paper develops a thesaurus based indexing system THINS that yields higher retrieval rate than other systems.by doing syntactic analysis of text data and matching them with index terms in thesauri partially.First,the system analyzes the input text syntactically by using the machine translation suystem MATES/EK and extracts noun phrases.After deleting stop words from noun phrases and stemming the remaining ones.it tries to index these with similar index terms in the thesaurus as much as possible. We conduct an experiment with CACM data set that measures the retrieval effectiveness with CACM data set that measures the retrieval effectuvenss of THINS with single term based one under HYKIS-a thesaurus based information retrieval system.It turns out that THINS yields about 10 percent higher precision than single term based one.while shows 8to9 percent lower recall.This retrieval rate shows that THINS improves much better than privious ones that only yields 25 or 30 percent lower precision than single term based one.We also argue that the relatively lower recall is cause by that CRCS-the thesaurus included in CACM datea set is very incomplete one,having only more than one thousand terms,thus THINS is expected to produce much higher rate if it is associated with currently available large thesaurus.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.109-115
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• 2016

A demand of high bearing capacity of piles to resist heavy static loads has been increased. For this reason, the utilization of large diameter PHC piles including a range from 700 mm to 1,200 mm have been increased and applied to the construction sites in Korea recently. In this study, in order to increase the flexural strength capacity of the PHC pile, the large diameter composite PHC pile reinforced by in-filled concrete and reinforcement was developed and manufactured. All the specimens were tested under four-point bending setup and displacement control. From the strain behavior of transverse bar, it was found that the presence of transverse bar was effective against crack propagation and controlling crack width as well as prevented the web shear cracks. The flexural strength and mid-span deflection of LICPT specimens were increased by a maximum of 1.08 times and 1.19 times compared to the LICP specimens. This results indicated that the installed transverse bar is in an advantageous ductility performance of the PHC piles. A conventional layered sectional analysis for the pile specimens was performed to investigate the flexural strength according to the each used material. The calculated bending moment of conventional PHC pile and composite PHC pile, which was determined by P-M interaction curve, showed a safety factor 1.13 and 1.16 compared to the test results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.67-73
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• 2017

Recently, the demand for large diameter piles has been rapidly increased in order to secure the allowable bearing capacity of pile foundation due to the increase of large structures such as high rise buildings. In this study, to improve the shear capacity of a conventional PHC pile, a large diameter composite PHC pile strengthened by in-filled concrete and shear reinforcement was manufactured. All the piles were tested according to the shear strength test method of Korean Standard. As a result of the shear test, the F-type piles which are produced without shear reinforcement occurred abrupt horizontal cracks after flexural and inclined shear cracks occurred. On the contrary, the FT-type piles which are produced with shear reinforcement exhibited stable flexural and inclined shear cracks uniformly over the entire pile without abrupt horizontal cracks. Furthermore, the maximum load of the large diameter composite PHC pile improved to 2.9 times in the F series, and more than 3.3 times in the FT series compared to the conventional PHC pile. This result indicated that FT-type piles had excellent composite behavior due to the shear reinforcement and effectively prevented the unstable growth of inclined shear cracks.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.1-9
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• 2018

The development of new technology and process in industrial Plant which builds integrated structures, facilities and systems. Has become a key element for strengthening its competitiveness. Although domestic industrial Plant has demonstrated excellence in technology with a persistent increase in order quantity and orders received, the technology gap between countries has narrowed due to global construction trend. Therefore, it is necessary to develop new technology that could help overcome constraints and limitations of the current one to follow the trend in the age of unlimited competition. This study has focused on assembly technology of Pipe-rack joint connection in an effort to strengthen technological competitiveness in industrial Plant. Through an analysis of earlier studies on Pipe-rack and a coMParative analysis of strengths and weaknesses of current assembly technology of it, a new design plan has been made to improve it efficiently. In doing this, standards for design factors of both structural and performance features have been drawn, and value of stress, strain, moment and rotation has been calculated using finite element analysis. As a result, installation technology of modular type Pipe-rack, which has not been developed in Korea and is differentiated from the current one, has been developed. It is considered that the technology reduces work time and saves cost due to simplified joint connection of steel structure, unlike the current one. Moreover, since it is installed without a welding process in the field, industrial accidents would be reduced, which is likely to have economic competitiveness and satisfy.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.7-13
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• 2007

We synthesized and investigated $La_{0.75}Sr_{0.25}FeO_3$ by Glycine Nitrate Process(GNP) method used as cathode materials for SOFC(solid oxide fuel cell). Optimized amount of glycine is 3.17 mol. ICP elemental composition analysis indicated that the stoichiometry of the synthesized powders have nearly nominal values. SEM images and XRD patterns reveal that the synthesized powder has uniform size distribution and high degree of crystallinity. The sample powders were isostatically pressed to form a pellet. The green body was sintered at $1200^{\circ}C$ and the relative density of the sintered specimens were measured by Archimedes mettled. We measured electrochemical performance of LSF by AC impedance spectroscopy. Resistance of LSF shows lower value than that of LSM throughout all temperature region. The anode-supported solid oxide fuel cell showed a performance of $342mW/cm^2(0.7V,\;488mA/cm^2)$ at $750^{\circ}C$. The electrochemical characteristics of the single cell were examined by at impedance method.