• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.1-6
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• 2023

PE piping, which has advantages in terms of construction convenience and economy, is widely used for underground burial in the domestic urban gas field. These PE pipes use squeeze-off in many sites to block gas flow during maintenance and repair work. Squeeze-off refers to a method of compressing a PE pipe to block fluid flow, and damage may occur due to the nature of construction in which the pipe is deformed by physical force. In order to prevent damage to PE pipes due to squeeze-off, the main points to be reflected in the squeeze-off operation procedures such as proper compression range, use pressure, and diameter were derived through damage assessment and confidential test according to the compression rate. The compression experiment for PE pipe damage assessment was conducted while changing the compression rate (20%~40%), the pressure of use (2.8 kPa, 25 kPa, 70 kPa), and the pipe diameters (63 mm, 90 mm, 110 mm). As a result of damage assessment according to the compression rate, damage occurred in pipes with compression rates of 45%(110mm) and 73%(63mm), which are for analyzing the effect of excessive compression. In addition, the leakage test was conducted using Ar(argon) during the squeeze-off, and as a result of the experiment, leakage occurred under the conditions of 70kPa and 110mm of pipe. As a result of this study, it was confirmed that squeeze-off for airtightness should be carried out in pipes within a range not exceeding 25 kPa and 90 mm pipes, and the appropriate compression rate to prevent damage to PE pipes is 30%.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.11-18
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• 2013

Cement concrete pavement offers long-term service life and excellent applicability for heavy traffic. It is easier to purchase and more durable and economical than the asphalt pavement. However, it is difficult to repair and rehabilitate compared to the asphalt pavement when it comes to the maintenance problem. Since the crack is the main reason of the damage of concrete pavement, it is necessary to control the early and long-term crack in the concrete pavement. In this experimental study, the basic performance tests have been carried out to investigate the effect of hybrid fibers which were composed of micro fibers with small diameter and high aspect ratio and macro fibers with large diameter and low aspect ratio on the concrete pavement, in which lower water ratio and larger aggregates were used compared to the general concrete mixture. The test results showed that the flexural strength and toughness of concrete pavement mixture have been increased with the use of hybrid fibers in the concrete pavement mixture, even though they were less effective compared to the normal concrete mixture. It was found that the hybrid fibers were effective to control the early shrinkage of the concrete pavement which is one of the main reasons of the damage in the concrete pavement.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.11
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• pp.4417-4422
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• 2014

ERCC2 is an essential component of the nucleotide excision repair pathway which is involved in the effective maintenance of genome integrity. Association studies on ERCC2 polymorphisms and glioma risk have yielded inconclusive results. This meta-analysis was performed to gain a better insight into the relationship between ERCC2 polymorphisms and glioma risk. A systematic literature search updated to December 2, 2013 was performed in the Pubmed and EMBASE databases. Crude pooled odds ratios (ORs) with their corresponding 95% confidence intervals (95% CIs) were used to estimate the association between ERCC2 polymorphisms and glioma risk under a suitable effect model according to heterogeneity. All analyses were performed using Review Manager 5 (version 5.2) and STATA (version 12.0). The combined results demonstrated rs13181 to be significantly associated with glioma risk (G allele versus T allele: OR=1.15, 95% CI=1.05-1.26, P=0.002; dominant model: OR=1.22, 95% CI=1.07-1.39, P=0.002; recessive model: OR=1.18, 95% CI=0.98-1.41, P=0.070). We also found that rs13181 acts in an allele dose-dependent manner (GG versus TT: OR=1.30, 95% CI=1.07-1.57, P=0.009; TG versus TT: OR=1.20, 95%=CI 1.05-1.37, P=0.009; trend test, P=0.004). However, no evidence was found in analyses for the association between other 3 ERCC2 polymorphisms (rs238406, rs1799793, and rs1052555) and susceptibility to glioma development. Our meta-analysis suggests that rs13181 is significantly associated with glioma risk in an allele dose-dependent manner, whereas, 3 other ERCC2 polymorphisms (rs238406, rs1799793, and rs1052555) may have no influence.

• Journal of the Society of Disaster Information
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• v.15 no.4
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• pp.479-492
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• 2019

Purpose: The purpose of this study is to accurately analyze the damage of bridges in order to determine whether fire bridges can be used continuously or to provide information on maintenance augmentation data. Method: XRD, SEM and EDS analyzes of concrete were carried out to estimate the fire temperature transferred to the structure, and analyzed by depth and area from PSCI beam and bottom plate concrete surface. Results: Test results G_12,11 for the fire zone concrete were confirmed to be affected by heat up to depth of 60mm and the temperature of the hydrothermal heat was above 1000℃. Also, the girder G_10,9,8 was relatively weakly damaged compared to G_12,11, and the degree of damage was confirmed to be affected by heat up to a depth of 40 mm. Conclusion: Based on the analyzed data, it is considered that if the repair / reinforcement and periodic inspection are carried out, the bridge can secure sufficient safety even considering the damage caused by the fire.

• Clean Technology
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• v.27 no.4
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• pp.297-305
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• 2021

In the domestic aluminum industry, the extrusion process is a major process accounting for more than 40% of the total production. However, most domestic aluminum extrusion companies produce aluminum using old equipment that is more than 30 years old. Extrusion press is when the equipment is not replaced before the wear and breakage of major parts occur, reducing productivity and increasing the defect rate compared to new equipment. The old extrusion press often loses part drawings, so it is difficult to repair them properly on-site and to remanufacture them due to the lack of technical skills for maintenance. Therefore, a systematic remanufacturing plan must be designed from dismantling the equipment. In this study, remanufacturing FMEA was devised to remanufacture old extrusion press. The risk priority was analyzed by considering the degree of damage to the recycled parts, the cycle due to breakage/damage during the extrusion process, and the value of recycling resources due to remanufacturing. To standardize the remanufacturing process, remanufactured FMEA was performed through part analysis according to the structural analysis of the extrusion press. In addition, remanufacturing priorities were selected for each part, while remanufacturing itself was studied for efficiency of resource circulation and product quality stabilization.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.71-80
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• 2010

Bridge deck is directly influenced by environment and vehicle load, it is easily damaged so that it requires an appropriate repair and retrofit. Therefore, developing a bridge deck with high durability is necessary in order to minimize the maintenance of bridge deck and use it to its design life. In this study, static test was carried out to evaluate a fatigue capacity of steel-concrete composite deck, which was newly developed by supplementing problems of existing reinforced concrete deck. Based on results from the static test, fatigue load was decided, and fatigue test was conducted under the constant amplitude repeated load. From the fatigue tests, the S-N curve regarding principle structural details of composite deck was made, and characteristics of fatigue behavior was estimated by comparing and evaluating it with fatigue design criteria. In addition, fatigue design guideline was presented. As a result, it is found that each structural details of composite deck proposed by this study, such as upper flange of corrugated steel plate and middle section of it, shear connector and lower flange of corrugated steel plate, is satisfying the fatigue strength.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.507-514
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• 2015

In recent years, the number of construction projects carried out to repair and reinforce newly built structures and facilities has been on the rise compared to the number of new construction projects, accounting for more than 90 percents of all construction projects carried out by specialty construction companies. However, as some of the ordering parties fill out the required tasks incorrectly, the wrong information on construction bids is announced, and the specialty construction companies that hold a license and technology are unable to get the job at the right time. As such, it is critical to prevent unnecessary time and expense related to the correction of incorrect bid announcements by providing accurate information and definitions, because the tasks of each specialty construction work stipulated in the framework act of construction industry are vague. Therefore, the causes and problems were analyzed based on the correction cases of bid information, and a plan that can address the problem will be proposed. The result of this study can be utilized as fundamental data to achieve an institutional improvement in the bidding service for the specialty construction companies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.3
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• pp.110-118
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• 2003

Spacer dampers maintain the constant gaps between each conductor in a bundle conductor-transmission line, and are installed at proper intervals to keep a line from all sorts of damages derived from the vibration energy caused by mechanical or electrical external factors. It is most important to embody a technology which considers difficulties of maintenance and repair, and has optimum elements in order to prevent accidents such as destruction by fire or the snapping of a wire by the effect of vibration phenomenon coming from transmission lint In the resent thesis, therefore, the analysis of vibratory characteristics of spacer damper is set up by analytical methods such as the analysis of conductor motion's governing equation, the equation of spacer damper's motion, spacer damper-fastened wire's motion in a span and the numerical analysis of finite difference method. Furthermore, the installation distance between spacer dampers was scrutinized by simulations of various vibration phenomena which change at any time as actual conditions do, and hereafter difference method. Furthermore, the installation distance between spacer dampers was scrutinized by simulations of various vibration phenomena which change at any time as actual conditions do, and hereafter we will be able to analyze all kinds of vibration phenomena coming from a boltless spacer damper with 6 bundle conductor for 765kV transmission line based on new analytical methods.

• Journal of Korean Society of Transportation
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• v.31 no.1
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• pp.37-46
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• 2013

Lane closure in freeway work zone due to maintenance and repair of freeway facilities results in abrupt change of traffic flow. Sudden change of traffic flow results strong interactions among vehicles, and reduces capacity compared to the ordinary traffic condition. Such capacity reduction is likely to cause congestion, traffic queues, and economic loss cost. This study aims to determine the base capacity for a short-term freeway work zone that can be used to establish a work zone schedule in advance without any traffic impact. First, the research collected detector data and schedule data of road works on all freeways in Korea. Second, the research determined 23 study sites finding the capacity values of work zone after matching two kinds of data. All study sites had varying characteristics regarding traffic flow being adjacent to work zone during road works. The capacity values were reviewed in terms of lane closure configuration, the types of work, and design speed. Finally, research proposed capacity values for a short-term freeway work zone with the design speeds of 100 kph, 120 kph and 1,700 pcphpl, 1,750 pcphpl, respectively.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.794-799
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• 2005

With the quantitative growth of the petroleum industry, the pipe facilities that connect each process increased significantly and the corresponding maintenance and repair costs of the pipe facilities increased as well. The diagnosis techniques to check a pipe efficiency while in operation are few in Korea, but in the advanced countries the pipe diagnosis using gramma-ray source was on-going research since 1960's. In this study, field experiments were performed to analyze the reasons for abnormal operation of the pipe connected to a distillation tower, and the degree of abnormality was estimated using a sealed gamma-ray source ($^{137}Cs$). Gamma radiation counts were measured by a detector (NaI) positioned outside the pipe-wall diametrically opposite to the gamma source. The results showed that a gas zone section's distribution pattern was different from the pattern of nearby fluid in a pipe. Th diagnosis technique using a gamma radiation source was proved to be an effective and reliable method, offering the information on the fluid distribution in pipe.