• Tribology and Lubricants
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• v.23 no.3
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• pp.130-133
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• 2007

Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube and support. The fretting wear of tube and support can threaten the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of tube-support is required. The fretting wear tests were performed with supporting grids and cladding tubes, especially after corrosion treatment on tubes, in water. The tests were done using various applied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tube materials can be predictable by obtaining the wear coefficient using the work rate model. Due to stick phenomena the wear depth was changed as increasing load and temperature. The maximum wear depth was decreased as increasing the water temperatures. At high temperatures there are the regions of some severe adhesion due to stick phenomena.

• Tribology and Lubricants
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• v.24 no.3
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• pp.129-132
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• 2008

Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube and support. The fretting wear of tube and support can threaten the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of tube-support is required. The fretting wear tests were performed with supporting grids and cladding tubes, especially after corrosion treatment on tubes, in water. The tests were done using various applied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tube materials can be predictable by obtaining the wear coefficient using the work rate model. Due to stick phenomena the wear depth was changed as increasing load and temperature. The maximum wear depth was decreased as increasing the water temperatures. At high temperatures there are the regions of some severe adhesion due to stick phenomena.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.61-68
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• 2018

In general, defects cause a lot of maintenance costs and serious damage to various stakeholders, such as the owners, contractors or occupants of apartments. For this reason, a systematic and efficient defect management method is needed to minimize defect disputes. This paper derives a defect classification framework and proposes a defect risk assessment model for different types of defects. For this purpose, 6,000 defect items are allocated to the defect classification framework; these items are associated with 34 apartment projects over ten years old. As a result of this analysis, it was confirmed that the defect risks are concentrated in the areas of RC and finishing work. Based on these results, it is necessary to prevent the major risks of defects according to their priority. Based on this research, it is judged that further research to develop a method of managing the risks of defects may be necessary.

• Geomechanics and Engineering
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• v.11 no.4
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• pp.571-585
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• 2016

The crest of the Pubugou central core rockfill dam (CCRD) cracked in the first and second impounding periods. To evaluate the safety of the Pubugou CCRD, an inversion analysis of the constitutive model parameters for rockfill materials is performed based on the in situ deformation monitoring data. The aim of this work is to truly reflect the deformation state of the Pubugou CCRD and determine the causes of the dam crest cracks. A novel real-coded genetic algorithm based upon the differences in gene fragments (DGFX) is proposed. It is used in combination with the radial based function neural network (RBFNN) to perform the parameters back analysis. The simulated settlements show good agreements with the monitoring data, illustrating that the back analysis is reasonable and accurate. Furthermore, the deformation gradient of the dam crest has been analysed. The dam crest has a great possibility of cracking due to the uncoordinated deformation, which agrees well with the field investigation. The deformation gradient decreases to the value lower than the critical one and reaches a stable state after the second full reservoir.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.509-516
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• 2004

The measurement of abnormal change of temperature(temperature anomaly) will help determine the safety of various engineering constructions, as the measurement in body often used to diagnose one's health. Temperature anomaly can be occurred in leakage or seepage of water flow in rocks, and in ground water table etc. Grouting materials injected in fractured rocks generate heat during hardening process. The degree of temperature change is associated directly with heat flow characteristics, that is, thermal conductivity, specific heat capacity. density of the surrounding rocks and can afford to assess the grouting efficiency. However, in practice, the use of traditional temperature measuring technique composed of only one single thermal sensor has been fundamentally limited to acquire thermal data sufficient to use for that, partly due to the time-consuming measuring work, partly due to the non-consecutive quality of data. Thus, in this paper, a new concept of temperature measuring technique, what we call, thermal line sensor technique is introduced. In this, the sensors with an accuracy of $0.02^{\circ}$ are inserted at regular intervals in one line cable and addressed by a control device, which enables to fundamentally enhance the capability of data acquisition in time and space. This new technology has been demonstrated on diverse field model experiments. The results were simply meant to be illustrative of a potential to be used for various kinds of temperature measurements encountered in grouting and leakage problems.

• Korean Journal of Health Education and Promotion
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• v.13 no.2
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• pp.167-183
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• 1996

Human teeth vary widely in color. Practitioner and patients are concerned with preventing and correcting discolored or dark teeth to achieve and maintain stain-free, white teeth. Tooth brushing cannot alter tooth color but it can remove adhering films and stains. The esthetics of natural dentition can be improved by bleaching and this process can be applied to intrinsically and extrinsically stained teeth. The need for a brighter, more attractive smile has made rapid growth in the market for tooth whiteners. There is no doubt these products work as whiteners, at least on mild to moderate stains, but the safety of these products are unclear. In this experiment, the effect of tooth whitener application on the color and microhardness of extracted human enamel was measured. RMS, RMT and NWT were used as tooth whiteners, and tooth paste(ETQ) and hydrogen peroxide solution(HPO) were used as controls. 35 caries-free extracted human molars were embedded and polished with the exposed enamel diameter of 4 mm. The tooth whiteners and control agents were applied according to the manufacturers' instructions or clinically simulated procedures for eight weeks, and measurements were repeated every two weeks. Value(L＊) difference was measured using Differential Colorimeter(Model TC-6FX, Denshoku Co., Japan), and microhardness was measured using microhardness tester(Mitsuzawa Seiki Co., Japan). The results were as follows; 1. After application of agents for eight weeks, the Vickers hardness increased significantly in the ETQ, RMS and RMT application group(p〈0.01), and that decreased significantly in NWT application group(p〈0.01), but in HPO application group there was no significant change. The change in microhardness was greatest in NWT application group(p〈0.01). 2. After application of tooth whiteners and controls for eight weeks, the value change of toothpaste application group was significantly lower than those of other agents groups(p〈0.01), and there was no significant difference in value(L＊) change among tooth whitener groups(p〉0.01). 3. The application of tooth paste and paste type tooth whitener made gradual value change, but hydrogen peroxide gel type tooth whitener and hydrogen peroxide solution made rapid value change during initial application period.

• Journal of KIBIM
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• v.5 no.3
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• pp.19-32
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• 2015

For decades, the productivity issue has been a primary concern for the all stake-holders who participate in domestic construction industry. Especially, between a whole life cycle of building, the construction phase's productivity problem makes or break the entire project. In this respect, the general construction company, who accept the order and construct the building(so called General Contractor), should consider various strategies, such as schedule management, cost management, quality management, inner-crew management, etc., for the productivity improvement., and almost of these management methods have been studied for a long time. But, the researches and studies about the specialty contractor, who construct the building directly in construction site were not sufficiently complete yet. This research begins as an idea which tries to apply the BIM(Building Information Modeling) into the tasks of Specialty contractors for their productivity improvement. And for the effective application of construction BIM to specialty contractors, establish of the BIM project execution plan for them, not the fragmentary adoption of BIM. Therefore, in this paper, we develop the BIM project execution plan for the reinforced concrete companies who conduct the framework construction which located on CP(Critical Path) Especially, we model the "Construction BIM Use List for the RC Work", "BIM Application Master Process" and "BIM Application Detailed Process", and general contractor who use these BIM uses list and process models can manage various specialty contractors about schedule, cost, earned value, quality, safety and environment management systematically.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1191-1202
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• 2013

The former researches on earthwork automation were mainly focused on GPS and sensor application, environment modelling, equipment path planning, work information management, and remote control etc. Recently, reducing $CO_2$ emission becomes one of main focuses for an automation research. In the case of earthwork operations, many kinds of construction machines or robots are involved, which can cause high level of $CO_2$ in a construction site. An effective earthwork plan and construction machine operation can both increase productivity and safety and decrease $CO_2$ emission level. In this research, some automation concepts for green earthworks are suggested such as a 3D construction site model, a 3D earthwork distribution based on two different earthwork methods, and an earthwork package construction method. A excel-based simulator is developed to generate the 3D earthwork distribution and to estimate the level of $CO_2$ emission for the given earthwork.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.536-551
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• 2017

With the advancement and deployment of leading-edge telecommunication technologies for sensing and collecting, computing related information, Cloud of Things (CoTs) has emerged as a typical application platform that is envisioned to revolutionize the daily activities of human society, such as intelligent transportation, modern logistics, food safety, environmental monitoring, etc. To avoid any possible malicious attack and resource abuse, employing hash functions is widely recognized as one of the most effective approaches for CoTs to achieve message integrity and data authentication. The Whirlpool hash function has served as part of the joint ISO/IEC 10118-3 International Standard by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). In this paper, we propose an effective differential fault analysis on Whirlpool in the byte-oriented random fault model. The mathematical analysis and experimental results show that 8 random faults on average are required to obtain the current 512-bit message input of whirlpool and the secret key of HMAC-Whirlpool. Our work demonstrates that Whirlpool and HMAC-Whirlpool are both vulnerable to the single byte differential fault analysis. It provides a new reference for the security analysis of the same structure of the hash functions in the CoTs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1187-1191
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• 2011

In this paper, the development of an adjustable load limiter is presented, which is a component of the seat belt. The adjustable load limiter is loaded at different levels for varied weights and heights of occupant. The recent regulation FMVSS 208 demands strict safety standards for different percentiles of dummy size. In this work, high- and low-level load conditions are proposed according to dummy scale and thoracic injury criteria. The suggested load conditions were verified by performing a sled test using the benchmark model. A dual-level load limiter has been developed on the basis of these tests. Experiments were conducted on the product performance, and finite element analysis was carried out; the results confirmed the points for improvement.