• Journal of Korean Association for Spatial Structures
• /
• v.13 no.4
• /
• pp.67-74
• /
• 2013

The Age-adjusted effective Modulus Method(AEMM) is one of the methods adopted for the construction stage analysis of concrete structures. The AEMM uses the aging factor to consider the effects of the varying concrete stress. In the aspects of computation time and the accuracy of the results, the AEMM is considered as one of most appropriate methods for construction stage analysis of tall building structures. Previous researches proposed appropriate values of the aging factor in the forms of graphs or using very simple equations. In this paper, an equation for estimating the aging factor as a function of rebar ratio in the section, compressive strength of concrete, notional member dimension, and age of concrete at the load application. The validity of aging factor proposed in this paper were examined by the comparison with the results of step-by step method.

• Korean System Dynamics Review
• /
• v.13 no.4
• /
• pp.5-31
• /
• 2012

This paper aims at investigating the dynamics between aging population and local finance. In recent years, the aging rate has been accelerating the pace. The trend implies that Korea is moving towards the aging society, presumably, with unprecedented speed in the world. Aging society's biggest problems are centered around the explosive growth of the financial needs. In particular, these problems are apt to appear more seriously in local governments, as most of them are confronted with high level of aging population and poor financial bases. Firstly, it analyzes how the population structure in the local government impacts local finance, income and expenditure. Based upon in-depth literature reviews, this study examines variables related to aging population and local fiance. Secondly, it focuses on a series of positive and negative feedback loops which would reveal the essence of the mutual interaction structure between aging population and local governments' fiscal behaviors.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.5 no.2
• /
• pp.13-19
• /
• 2009

As the operating time in nuclear power plants (NPPs) increases, the integrity of nuclear components may be continually degraded due to aging effects of systems, structures and components. Recently, a number of NPPs are being operated beyond their design life to produce more electricity without shutting down. The critical issue in extending a lifetime is to maintain the level of safety during the extended operation period while satisfying the international regulatory standards. Therefore, it is beneficial to build a monitoring system to measure an aging status. In this paper, the Aging Monitor (AM) based on lots of aging database obtained from the operating plants and research results on the aging effects was developed to monitor, manage and evaluate the aging phenomena systematically and effectively in NPPs. The AM for the CANDU is divided into 6 modules: (1) Aging Alarm/Coloring Monitor, (2) Aging Database, (3) Aging Document, (4) Real-time Integrity Monitor, (5) Surveillance and Inspection Management System, and (6) Continued Operation and Periodic Safety Review (PSR) Safety Evaluation. The proposed system is expected to provide the integrity assessment for the major mechanical components of an NPP under concurrent working environments.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.10
• /
• pp.1411-1417
• /
• 2015

The installation of PV system to the power distribution system is being increased as one of solutions for environmental pollution and energy crisis. However, the efficiency of PV system is getting decreased because of the aging phenomenon and several operation obstacles. Therefore, The technology development of aging diagnosis of PV modules are required in order to improve operation performance of PV modules. This paper proposes evaluation algorithm for aging state in PV modules by using the electrical characteristics of PV modules and environmental factors. And also, this paper presents a operation evaluation system of PV modules based on the proposed aging diagnosis algorithm of PV modules. From the simulation results of proposed evaluation system, it is confirmed that the proposed algorithm is a useful tool for aging diagnosis of PV systems.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.41 no.1
• /
• pp.37-43
• /
• 2009

In this study, the physical properties of base paper for the manufacture of mulching mat for afforestation seedling were investigated. The base paper for mulching mat was prepared by stock conditions of PAE and AKD addition into the screened slurry of KOCC for the strengthening effects of wet tensile and burst strength. The optimum additions of PAE and AKD were considered at 2% and 0.5%, respectively. The accelerated aging by ISO 5630-1 and wet heat aging method under hot water for 2 kinds of commercial mulching and wet strength paper were compared with the base paper prepared for mulching mat manufacture. The accelerated aging test for the base paper prepared for mulching mat manufacture resulted in the same tendency of physical properties as two kinds of commercial products. However, the results of wet heat aging test under hot water indicated that the physical strength for base paper prepared was much higher than others. In addition, the opacity behavior for base paper prepared was enough effects to obstruct weeds growth by isolating transmission of sunlight.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2011.04a
• /
• pp.235-241
• /
• 2011

Effects of thermal aging on color variations of various papers were evaluated. With thermal aging, most of papers showed a special trend in $a^*$-$b^*$ plane: $a^*$ (red-green) values of the samples were reduced at beginning and after a turning point it was increased while $b^*$ (blue-yellow) was kept increased (yellowing of paper). In case of filter paper which consists of chemical pulps, the changes in $a^*$ value was occurred late compared with other samples. In case of the copy paper with optical brightening agent, the turning point in $a^*$ was not observed while a constant increase in $b^*$ was observed. In case of color paper, no specific trends in $a^*$-$b^*$ were found.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1549-1551
• /
• 2001

Cyclic aging for 14 days is performed to remove a large amount of the volatiles found in freshly manufactured cable. In this paper, we examined lightning impulse characteristics of 22.9 kV CV power cable before and after cyclic aging for 14days. As the result, the breakdown voltage after aging under normal temperature was lower than that before aging, and the breakdown voltage after aging under hot temperature was lower than that before aging. We found that the dispersion of lightning impulse breakdown voltage before 14 cyclic aging test were reduced rather than those after 14 cyclic aging test.

• Nuclear Engineering and Technology
• /
• v.53 no.4
• /
• pp.1357-1368
• /
• 2021

This paper presents thermal aging effect on fracture toughness properties of GTAW (gas tungsten arc welding) and SMAW (shielded metal arc welding) of 316L stainless steels, and investigates the applicability of the existing three thermal aging models for CASS (cast stainless steels). Thermal aging was carried out at 350 ℃ for up to 15,000h and at 400 ℃ up to 8,000h. After aging, tensile and fracture toughness tests using 0.5T C(T) specimens were carried out at room temperature and at 288 ℃. Comparing with the predictions using three (ANL, French and H3T) thermal aging models for CASS show that the predictions can be very non-conservative at operating temperature, and thus that the existing thermal aging models for CASS cannot be applied to the welded stainless steels.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.47 no.6
• /
• pp.130-138
• /
• 2015

This study was conducted to investigate the effect of the strengthening treatment of methyl cellulose (MC) on properties and aging characteristics of the dewaxed papers during humid heating aging. Beeswax-treated Hanji was dewaxed by the supercritical fluid extraction method, and subsequently the strengthening treatment was performed with MCs having three different viscosities. MC was first applied by dipping a dewaxed paper into a MC solution whose concentration was controlled from 0.5% to 1.5%. After the strengthened papers were artificially aged at $80^{\circ}C$ and 65% RH, the changes in optical and mechanical properties of the samples were evaluated. The results show that viscosity and especially pick-up of MC influenced the strengthening efficiency and aging characteristics of dewaxed paper. Strength was increased with the MC coating weight; in addition, strengthening with MC improved preservability of the dewaxed paper. The optimum conditions for the strengthening with MC was found to be the coating ratio of 4% with 1500 cP MC.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.46 no.4
• /
• pp.76-84
• /
• 2014

Preventive conservation is one of most important issues in the field of conservation for paper-records. Many researchers have been studied environmental factors such as effects of humidity, temperature, biological attack and air pollutants. Air pollutants strongly associated with oxidative and hydrolytic degradation of cellulose. It is important to control air pollutants in storage environment to improve stabilities of conservation environment. Four paper samples have been analyzed for their accelerated aging characteristics by air pollutants, sulfur dioxide, nitrogen dioxide, ozone, carbon monoxide. Physical and optical properties and weight molar masses(Mw) showed that interactions between air pollutants and paper sample. Nitrogen dioxide, ozone caused severe damage to cellulose in paper by hydrolytic and oxidative decompositions during aging.