• New & Renewable Energy
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• v.17 no.2
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• pp.24-31
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• 2021

Renewable energy has become more popular with the increase in the use of solar power. Consequently, the disposal of defective and old solar panels is gradually increasing giving rise to a new problem. Furthermore, the efficiency and power output decreases with aging. Researchers worldwide are engaged in solving this problem by developing eco-module technologies that restore and reuse the solar panels according to the defect types rather than simple disposal. The eco-module technology not only solves the environmental problem, but also has economic advantages, such as extending the module life. Replacement of encapsulants contributes to a major portion of the module maintenance plan, as the degradation of encapsulants accounts for 60% of the problems found in modules over the past years. However, the current International Electrotechnical Commission (IEC) standard testing was designed for the commercialization of solar modules. As the problem caused by long-term use is not considered, this method is not suitable for the quality assurance evaluation of the eco-module. Therefore, to design a new accelerated test, this paper provides an overview of EVA degradation and comparison with the IEC and accelerated tests.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.64-72
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• 2020

DELAY M9 is an ammunition used in combination with the fuse M904 and M905 of aviation drop-off ammunitions. Due to the properties of the ammunition, the performance or safety of the ammunition cannot be verified until it is used, because of its one-time function, no reproduction and is finally destroyed at the same time. Long-term storage of ammunition in use by the army is inevitable due to its operational characteristics, and a test evaluation is required to maintain and verify the performance of stored ammunition for immediate use in case of emergency. This paper estimates the reliability and shelf life of the DELAY M9 ammunition by using the test data obtained through ASRP performed from the past to the present. The result of the performance evaluation test for the currently stored DELAY M9 ammunition is analyzed, and the reliability and shelf-life of the stored ammunition are assessed by examining the number of defects according to the storage time and production year. This research result can be used to manage the stored ammunition, such as ASRP planning and evaluation test, result analysis and munition state decision.

• Journal of muscle and joint health
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• v.3 no.1
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• pp.37-49
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• 1996

The joint diseases threaten modern people's healthy life. They bring about a long pain, an anasarca, loss of joint function or even deformation and rigidity of joint, limiting people's ordinary activities much. The chronic joint patients may be subject to some hypochondria caused by anxiety for their life, social isolation, financial problem and physical disability. Therefore, this population should continue to be duely taken care of by medical personnels. In particular, nurses should adequately help these people to recover and improve their health through suitable adaptations. With such basic conceptions in mind, this study was aimed at reviewing these patients' conditions in their ordinary life before and after a plastic operation for artificial joint replacement as well as their satisfaction with their life. For this purpose, those patients who underwent some plastic operations for artificial joint replacement at university hospitals in Seoul from January 2, 1993 to June 30, 1995 were selected as the population of this study. Among them, 87 people were randomly sampled to answer a questionnaire designed specially. For the surveying tools, Jette's (1980) scale was applied to address the sample people's inconveniences experienced and supports received in their ordinary life, while the scale of Wood, Wylie & Sheafer was used to measure their satisfaction with their life. The collected data were analyzed for percentiles, means, SD, t-test and Pearson's correlations. The results of survey can be summarized as follows ; As a result of t-test the frequencies of other people's support before and after the plastic operation, it was disclosed that those who underwent the operation were supported less frequently. In addition, as a result of t-testing their satisfaction with life before and after the operation, it was found that the operation increased their satisfaction with life significantly. Meanwhile, as a result of t-test inconveniences, frequencies of supports and life satisfaction before and after the plastic operation for artificial knee replacement, it was disclosed that only the inconveniences were significantly reduced after the operation. In contrast, the t-test the variables before and after the plastic operation for artificial hip replacement, it was found that only the frequencies of other people's supports were significant reduced after the operation. Furthermore, the differences 6 months, one year and two years after the plastic operation for artificial joint replacement were t-tested on the variables. As a result, it was disclosed that people's inconvenience, frequencies of supports and life satisfaction were not improved 6 months after the operation but their frequencies of supports decreased significantly one year after, while their inconveniences and life satisfaction were significantly improved two years after. As a result of analyzing the variables with Pearson's correlations, inconveniences and frequency of supports were negatively correlated significantly with the life satisfaction. In conclusion, the plastic operation for artificial joint replacement significantly improved people's living inconveniences, reduced their frequency of other people's support and enhanced their satisfaction with life. To break don the plastic operation for artificial knee replacement improved patients' inconveniences, while the plastic operation for artificial hip replacement not only improved patients' inconveniences but reduced the frequencies of other people's support also. Finally, the finding that the plastic operation for artificial joint replacement brought about the improvement two years after suggests that this period is needed for the patients to adapt themselves to the post-operation conditions.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.13-22
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• 2005

Using recycled aggregate from demolished concrete structures provides a peat opportunity fur conserving natural resources. In many parts of world, virgin aggregate deposits have been depleted, and transporting aggregates over long distances can be much more expensive than using a low-cost recycled aggregate. In Korea, about 7-million tons of concrete occurs annually, out of this, about 2-3 million tons are available for recycling. This study is to present the method of utilizing the recycled aggregate. The recycled aggregate concretes were made for compressive strength test, flexural strength test and fatigue test using w/c of 40, 50 and 60%. The replacing rates of recycled aggregate to virgin aggregate were 0, 25 and 50%. The purpose of this study is to compare the fatigue lift of recycled aggregate concrete with that of virgin aggregate concrete. It was shown that the fatigue life of recycled concrete was function of recycled aggregate replacement ratio and water cement ratio.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.951-956
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• 2008

The high temperature creep properties of the generating plant's high temperature tube, pipe and header and such are very significant in accordance with long-time exposure to the high temperature and pressure environment. Not only this, but as the welding procedure is compulsory for the cohesion of components, the creep properties regarding the local microstructures of steel weldment are very important. In order to understand the creep properties regarding the local microstructures of steel weldment, the SP-Creep test which is easy to get sample from the field component was conducted. The local microstructure of steel weldment, that is, W.M. and B.M.'s microstructures were observed using the SEM. The rupture time of W.M. was longer as 110 % averagely in a same condition, which is the consequence of the difference of the microstructure. Each lethargy coefficient of B.M. and W.M. is evaluated by the relation among the temperature, load and the rupture time from SP-Creep Test. The life estimation equation can be induced by the transformation of Power-law. B.M. and W.M. for each $550\;^{\circ}C$ and $575\;^{\circ}C$, the very similar to normal temperature of the domestic thermal power generation in working, are estimated.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_3
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• pp.1239-1246
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• 2022

This paper introduces the effect of grease on the degradation characteristics of bearings used as key components of packaging equipment and automation systems. Bearings parts are installed to fix and support the rotating body of the system, and performance degradation of the bearings has a great effect on the life of the system too. When bearings are used in various devices and systems, the grease is applied to reduce friction and improve fatigue life. Determining the type of lubricant (grease) is important because it has a great influence on the operating environment and lifespan and ensures long lifespan of systems and facilities. However, studies that simultaneously compared and analyzed the change in mechanical degradation characteristics and the comparison of chemical degradation characteristics according to grease types under actual operating conditions are insufficient. In this paper, three types of small harmonic drive, high-load reducer, and low-load reducer grease used in power transmission joint modules are experimentally selected and finally injected into ball bearings with a load (19,500N) to improve bearing durability. Degradation characteristics were tested by attaching to test equipment. At this time, after the durability test under the same load conditions, the mechanical degradation characteristics, that is temperature, vibration according to the three greases types. In addition, the chemical degradation characteristics of the corresponding grease was compared to present the results of mutual correlation analysis.

• The Korean Journal of Pesticide Science
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• v.13 no.1
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• pp.39-44
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• 2009

This study was conducted to evaluate the actual risk of fipronil on worker honey bees (Apis mellifera L.) through acute contact toxicity test, acute oral toxicity test, toxicity of residues on foliage test, and small scale field test. The $48h-LD_{50s}$ of fipronil SC on honeybee were $0.005{\mu}g$ a.i./bee in acute contact toxicity test and $0.004{\mu}g$ a.i./bee in acute oral toxicity test, respectively. In toxicity of residues on foliage test, fipronil showed over 90% of mortality during 28days after treatment at recommended application rate. The $DT_{50}$ of dislodgeable foliar residue was 9 days. Finally, In small scale field test, fipronil showed similar toxicity in the residues on foliage test. It was concluded that fipronil has very high acute toxicity and long residual toxicity to honeybee. Therefore, fipronil is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area. To protect honeybee and wild pollinators from outdoor use of fipronil, ultimately it should need to limit for only indoor use to prevent pollinators from unintentionally exposure of fipronil.

• School Mathematics
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• v.9 no.4
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• pp.507-521
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• 2007

The purpose of this study was to investigate the effects of memory retention of mathematical concepts in multiplication in the inquiry-based pantomime instructions. Three months later after the pre-test, a comparison was made between traditional class (TC) and class with the inquiry-based pantomime (IP) approach in terms of students retention of mathematical understandings. Results of the study indicated that the If instructions promoted effective long-term retention of knowledge. We concluded that instructional strategies that promoted active engagement in learning using life examples and drawings produced effective long-term retention of knowledge.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.413-433
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• 2010

South Dakota is an important agricultural state in the United States with annual cash receipts from agricultural products exceeding $9 billion dollars. This production is possible because of large areas of productive soils. This publication describes the general characteristics and qualities of the major soil groups recognized in South Dakota. The soil forming factors are briefly described, soil classification is introduced, and the genesis of typical Udalf and Ustoll soils are discussed. Soil management issues impacting the use of SD soils are considered. Long-term (>70 yrs) cultivation has significantly reduced surface soil organic carbon levels (>30% reduction) when compared to non-cultivated soil. Soil test phosphorus levels significantly increased in cultivated fields due to commercial P fertilization. The major long-term production problems for SD soils are conservation of soil moisture, organic matter and nitrogen losses, fertility management, and wind and water erosion control.

• Smart Structures and Systems
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• v.6 no.3
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• pp.263-275
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• 2010

In the last decade, wireless sensor networks have emerged as a promising technology that could accelerate progress in the field of structural monitoring. The main advantages of wireless sensor networks compared to conventional monitoring technologies are fast deployment, small interference with the surroundings, self-organization, flexibility and scalability. These features could enable mass application of monitoring systems, even on smaller structures. However, since wireless sensor network nodes are battery powered and data communication is the most energy consuming task, transferring all the acquired raw data through the network would dramatically limit system lifetime. Hence, data reduction has to be achieved at the node level in order to meet the system lifetime requirements of real life applications. The objective of this paper is to discuss some general aspects of data processing and management in monitoring systems based on wireless sensor networks, to present a prototype monitoring system for civil engineering structures, and to illustrate long-term field test results.