• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.136-149
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• 2011

Large portion of the domestic bridges are slab bridges reflecting the geographical characteristic of the country, where exists lots of inclines and small winding brooks. Many of the slab bridges are damaged and superannuated as they become obsolete. Deterioration is accelerated when the traffic density becomes large and heavy vehicles pass frequently. A strengthening method for deteriorated slab bridges was studied in this work. The examined net-type strengthening method uses both longitudinal and transverse prestressing for strengthening. In this way, the deflection at the center of the slab can be better controlled, and consequently, the slab is more efficiently strengthened. Three slab specimens were fabricated for the experimental test and subjected to three different loading conditions, and the load bearing capacities and deflections of slabs were examined. Flexural stiffness of slabs increased by 30.7~107.3%, and deflection of slabs decreased by 27.6~52.2% after net-type strengthening. The net-type prestressing is efficient to the strengthening for the center of a slab, and its efficiency is also valid under eccentric loadings. Since extra prestress forces can be added in the future, if necessary, the net-type strengthening system is advantagous for the maintenance and repair of slab bridges.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.52-59
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• 2018

To control chloride attacks which is a representative deterioration in RC(Reinforced Concrete) structures, many studies have been conducted. Above all, a method using mineral admixture was known to be effective for corrosion protection. In this study, durability test about chloride attacks was carried out for concrete specimens containing FA(Fly Ash)-representative concrete mineral admixture and OPC concrete specimens considering 3 different levels of W/B(Water to Binder). Accelerated chloride diffusion coefficient tests referred to Tang's method, total passed charge tests referred to ASTM C 1202, and compressive strength tests based on KS F 2405 were performed at each target age day. Also, based on previous studies of 28 days, time-parameter which is a key parameter for diffusion behavior is evaluated and its relations with compressive strength at the age of 365 days is evaluated. After the age of 49 days, chloride resistance of FA concrete is much improved than that of OPC concrete, which arose out of stable hydrates due to pozzolan reaction of fly ash. Time-parameter of FA concrete is evaluated to be about 1.5 times larger than that of OPC concrete. Also, time-parameter of FA concrete has a linearly decreasing relation while that of OPC concrete has a linearly increasing relation with compressive strength development.

• Journal of the Korean Society of Tobacco Science
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• v.31 no.2
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• pp.69-74
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• 2009

Potato Virus Y (PVY), PVY-vein necrosis strain, causes severe damage at growth, yield and leaf quality on flue-cured tobacco in Korea. The development of PVY resistant flue-cured varieties without quality deterioration is therefore urgently desired. The flue-cured tobacco, KF120 (Korea Flue-cured 120), was a male-sterile (ms) $F_1$ hybrid derived from the cross between msKF117 and KF0007-7. msKF117 was developed from the cross of NC82 with N. africana and KF0007-7 was developed from the cross of KF117 with NC82. The agronomic characteristics and disease resistance of KF120 was evaluated during 2006-2007 field performance test. It showed better growth characteristics and yield performance than standard cultivar KF109. It had 2 more leaves per plant, flowered 2 days later than KF109. The yield of cured leaf of KF120 was increased by about 5% compared to KF109. The chemical composition and physical properties of the cured leaf of KF120 were as much acceptable as those of KF109. KF120 showed high resistance to PVY compared to KF109. It showed a similar mode of resistance to bacterial wilt and black shank as was found in KF109.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.6
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• pp.973-980
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• 2000

This study was conducted to evaluate the quality of the cold air dried anchovies (CA), and compared with those of sun-dried anchovies (SA) and hot air dried anchovies (HA). Peroxide value increased, while ratio of percentage of (20:5+22:6) to that of 16:0 decreased during boiling and drying. The extents of change were CA>SA>HA in the order. In the case of CA, lightness was higher, but redness, yellowness and degree of browning was lower than in SA and HA. From the results of lipid properties, color test and sensory evaluation on color and rancidity odor, lipid deterioration was the lowest in CA of all boiled dried anchovy. Favorite properties such as a hot-water soluble nitrogen content and sensory evaluation on color and appearance of CA was superior to that of SA and HA. The nutritional properties (total amino acid contents, mineral contents and fatty acid compositions) of CA was similar to that of SA, but was superior to that of HA. Consequently, CA was recognized as a boiled dried anchovy with the most quality.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.307-314
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• 2002

Utilization of demolished-concrete as recycled aggregate has been researched for the purpose of substituting for insufficient natural aggregate, saving resources and protecting environment. There, however, are some Problems not only the large difference of dualities in recycled aggregates but also a little deterioration of mechanical properties in recycled aggregate concrete in comparison with that of natural aggregate concrete. In this study, the test results of freez and thaw durability of concrete with demolished-concrete recycled aggregate(DRA) arc as follows. Improvement of crushing process is an important assignment because that adhered mortar on source-concrete recycled aggregate(SRA) and DRA highly affects thc qualifies of recycled aggregate. The compressive strength of recycled aggregate concrete was not highly different in comparison with that of control concrete. But the resistance to penetration of Cl in recycled aggregate concrete was shown smaller than that of control concrete because of adhered mortar on recycled aggregate. The resistance to frcezing and thawing of recycled aggregate concrete was highly different due to adhered mortar on recycled aggregate, and durability factor of concrete with NA-SRA and DRA was more decreased than that of control concrete. On the other hand, durability factor of concrete with AA-SRA was larger than that of control concrete. It, therefore, is necessarily required that recycled aggregate including adequate entrained air should be used for satisfying the freez and thaw durability of recycled aggregate concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.149-156
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• 2016

It has been well known that concrete structures exposed to chloride and sulfate attack environments lead to significant deterioration in their durability due to chloride ion and sulfate ion attack. The purpose of this experimental research is to evaluate the long-term durability against chloride ion and sulfate attack of the alkali activated cementless concrete replacing the cement with ground granulated blast furnace slag. For this purpose, the cementless concrete specimens were made for water-binder ratios of 40%, 45%, and 50%, respectively and then this specimens were cured in the water of $20{\pm}3^{\circ}C$ and immersed in fresh water, 10% sodium sulfate solution for 28, 91, 182, and 365 days, respectively. To evaluate the long-term durability to chloride ion and sulfate attack for the cementless concrete specimens, the diffusion coefficient for chloride ion and compressive strength ratio, mass change ratio, and length change ratio were measured according to the NT BUILD 492 and JSTM C 7401, respectively. It was observed from the test results that the resistance against chloride ion and sulfate attack of the cemetntless concrete were comparatively largely increased than those of OPC concrete irrespective of water-binder ratio.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.3
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• pp.302-308
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• 2009

This study was performed to investigate the effect of dietary medicinal herb extract mix (MHEM, mulberry leaf : Japanese honeysuckle : goldthread＝48.5:48.5:3.0) on antioxidative activity of chicken thigh meat. The dietary treatments consisted of a corn-soybean meal basal diet (control), basal diet with 0.3% and 1% MHEM. At the end of the feeding trial, thigh meat samples were collected and stored in a refrigerator at $4^{\circ}C$ to be analyzed on day 0, 3, 7 and 14. The MHEM did not affect proximate composition of the thigh meat. Total phenol contents of the thigh meats in treatment groups were higher than that of the control (p<0.05). 1,1-Diphenyl-2-picrylhydrazyl radical scavenging activity were higher in dietary treatment group. 2-Thiobarbituric acid reactive substances values of the treatment group were lower than that of control at day 7 and 14 and the added level also affected the inhibition of lipid oxidation of thigh meat. In sensory test, panelists preferred treatment group at day 7 and 14. Therefore, results indicate that dietary MHEM added to chicken may retard the oxidative deterioration of chicken thigh meat during cold storage.

• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.91-97
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• 2007

Recently, during the past five years, accidents of gas boiler using city gas have occurred 7.4 times more than those which use LP gas. The number of accidents has increased since the use of city gas boilers has increased. These boiler accidents resulted in 87% death from poisoning of CO, and casualty of the accidents was 4.3 times more than that of other types of accident. Hence this study makes the cause of accidents clear by separation the exhaust tube which is the cause of CO poisoning. Also, this study will establish the safety of heat-resistant silicon through testing the performance of heat-resistant silicon. The experiment showed that common silicon started hardening at $56^{\circ}C$ while the heat-resistant silicon did not begin carbonization until $606^{\circ}C$. Besides at the temperature of $150^{\circ}C$ which is the normal temperature of exhaust tube, common silicon leaked on the pneumatic test after deterioration, but the heat-resistant silicon maintained its original property. With these results, we judge that we can reduce the casualty by CO poisoning if we use the heat-resistant silicon to the connector of he exhaust tube.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1976-1985
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• 2015

The amount of packets in palyout buffer of video streaming receiver can be changed by network condition, and saturated and exhausted by the delay and jitter. Especially, if the amount of incoming video traffic exceeds the maximum allowed playout buffer, buffer overflow problem can be generated. It makes the deterioration of video image and the discontinuity of playout by skip phenomenon. Also, if the incoming packets are delayed by network confusion, the stop phenomenon of video image is made by buffering due to buffer underflow problem. To solve these problems, this paper proposes the video streaming receiver with token bucket scheme which automatically establishes the important parameters like token generation rate r and bucket maximum capacity c adapting to the pattern of video packets. The simulation results using network simulator-2 (NS-2) and joint scalable video model (JSVM) show that the proposed token bucket scheme with automatic establishment parameter provides better performance than the existing token bucket scheme with manual establishment parameter in terms of the generation number of overflow and underflow, packer loss rate, and peak signal to noise ratio (PSNR) in three test video sequences.

• Journal of the Korean Solar Energy Society
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• v.30 no.6
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• pp.73-80
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• 2010

This study was conducted to estimate the relative performance of modules with changed characteristics due to long term exposure to the outdoor environment, with a specially made test device for simultaneous measurement of real time power output from the photovoltaic array, taking into account the inclined panel, direct irradiation, power being generated, temperature as well as the optimal analysis timing. In terminology description, M is an abbreviation of module and Group A, Group B are 10 modules series connection (1~10 of M), (11~20 of M) for each of them respectively. The overall mean voltage difference of M-18 with the lowest power output and M-14 with the highest output is-2.13V and it was identifiable that voltage difference was more concentrated to Group B. In addition, in case of M-2 and M-7, M-8, when compared with M-14, the overall mean voltage difference was -0.92V, -1.56 and -0.91V respectively showing the more concentration to Group A. When the temperature of module went up by $1^{\circ}C$, the mean voltage was reduced by 0.35V. For current, Group A was lower than Group B by-0.022A and the ratio of each group was 49.68% and 50.32% respectively, presumably the module with deteriorated properties were more concentrated to Group A relatively. From the comparison of relations with the comprehensive accumulation, M-2, M-7, M-8, M-16 and M-18 were those with deterioration of performance to the worst, thereby requiring precision examination. In comparative efficiency, M-14 was the most excellent one as 12.19% while M-18 as 10.53% was identified that its efficiency was comparatively rapidly reduced.