• 한국정밀공학회지
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• 제15권1호
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• pp.109-116
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• 1998

This paper is concerned with effective operating method of pneumatic on-off valves for improving position control accuracy, valve life-time and position settling time using modified pulse width modulation with dead-zone (MPWMD). The pneumatic system using on-off valves has advantage of simple construction and low cost compared with a system with servo-valves. The performance of the proposed control method is investigated experimentally for the position control of a pneumatic cylinder using on-off valves. Experimental results show that the proposed algorithm for valve operation can be used to obtain fast and accurate position control compared to the conventional PWMD algorithm. It is also shown that the use of the proposed MPWMD algorithm for the position control significantly reduces the number of valve switching and noise.

• Journal of Advanced Marine Engineering and Technology
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• 제21권5호
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• pp.482-490
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• 1997

The effects of strain amplitude. test temperature and stress on the fatigue properties for Ti-Ni wires were investigated using a rotary bending fatigue tester specially designed for wires. The fatigue test results were discussed in connection with the static tensile properties. The DSC measurement was conducted after fatigue test in order to clarify the change of transformation behavior due to the progress of fatigue. Under the temperature below or near the Af, the strain amplitude($\varepsilon_a$)-failure life (Nf) curve showed to be composed of three straight lines with two turning points. Of the 2 turning points, the upper one was coincident with the elastic limit strain and the lower one with the proportional limit strain. With rising of the test temperature above Af, the pattern of $\varepsilon_a$-Nf curve changed gradually to composition of 2 straight lines. The $\varepsilon_a$-Nf curve shifted depending on test temperature. In the short and medium life zones, the higher the temperature was, the shorter the fatigue life. However, in the long life zone, above the Af temperature, the fatigue life was not affected by the temperature. The transformation enthalpy measured after fatigue test was dependent on Nf, $\varepsilon_a$, and test temperature.

• Computers and Concrete
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• 제15권4호
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• pp.589-606
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• 2015

It is well-documented that the major deterioration of coastal RC structures is chloride-induced corrosion. Therefore, regional investigations are necessary for durability based design and evaluation of the proposed service life prdiction models. In this paper, four reinforced concrete jetties exposed to severe marine environment were monitored to assess the long term chloride penetration at 6 months to 96 months. Also, some accelerated durability tests were performed on standard samples in laboratory. As a result, two time-dependent equations are proposed for basic parameters of chloride diffusion into concrete and then the corrosion initiation time is estimated by a developed probabilistic service life model Also, two famous service life prediction models are compared using chloride profiles obtained from structures after about 40 years in the tidal exposure conditions. The results confirm that the influence of concrete quality on diffusion coefficients is related to the concrete pore structure and the time dependence is due to chemical reactions of sea water ions with hydration products which lead a reduction in pore structure. Also, proper attention to the durability properties of concrete may extend the service life of marine structures greater than fifty years, even in harsh environments.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제2권3호
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• pp.153-165
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• 2021

The objective of this study was to provide basic data for the conservation of wetland ecosystems in the Civilian Control Zone and the management of Yongyangbo wetlands in South Korea. Yongyangbo wetlands have been designated as protected areas. A field survey was conducted across five sessions between April 2019 and August of 2019. A total of 248 taxa were identified during the survey, including 72 families, 163 genera, 230 species, 4 subspecies, and 14 varieties. Their life-forms were Th (therophytes) - R₅ (non-clonal form) - D₄ (clitochores) - e (erect form), with a disturbance index of 33.8%. Three taxa of rare plants were detected: Silene capitata Kom. and Polygonatum stenophyllum Maxim. known to be endangered species, and Aristolochia contorta Bunge, a least-concern species. S. capitata is a legally protected species designated as a Class II endangered species in South Korea. A total of 26 taxa of naturalized plants were observed, with a naturalization index of 10.5%. There was one endemic plant taxon (Salix koriyanagi Kimura ex Goerz). In terms of floristic target species, there was one taxon in class V, one taxon in Class IV, three taxa in Class III, five taxa in Class II, and seven taxa in Class I. Three invasive alien species (Ambrosia trifida L., Ambrosia artemisiifolia L., and Humulus japonicus Siebold & Zucc) were observed. For continuous conservation of Yongyangbo Wetlands, it is necessary to remove invasive alien plants and block the inflow of non-point pollutants.

• 대한조선학회논문집
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• 제43권2호
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• pp.213-219
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• 2006

Low cycle fatigue cracks are mainly detected at discontinuous welded locations with high stresses under repeated cyclic static loads due to cargo leading and unloading. Theoretical and analytical methods have been used for evaluation of local stress and strain which have an effect on a prediction of fatigue life, but those have difficulties of considering stress concentration at notched location and complicated material behavior of welded joint or heat affected zone. Electronic speckle pattern interferometry(ESPI) system is nondestructive and non-contact measurement system which can get the relatively accurate full field strain at critical positions such as welded zone and structural discontinuous location. In this study, local strain was measured on welded cruciform joint by ESPI system and then low cycle fatigue test was performed. Effect of local strain on low cycle fatigue life was examined by measured values using ESPI system. Moreover, experimental fatigue life was compared with established S-N curves using theoretical local strain and stress calculated by Neuber's rule.

• Animal Systematics, Evolution and Diversity
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• 제40권2호
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• pp.140-146
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• 2024

A taxonomic examination of Zygophylax species collected from the subtidal zone of Seongsan Ilchulbong in the east of Jeju Island and a reexamination of the voucher specimens previously described as Z. biarmata were conducted. Through this study, the species previously reported as Z. biarmata in Korea was redescribed as Z. pacifica, and the specimens from Seongsan Ilchulbong were confirmed to be Z. biarmata. Zygophylax biarmata has two nematothecae on the apophysis of the hydrotheca, a clear distinction between the apophysis and the pedicel of the hydrotheca, and much smaller hydrothecae, whereas Z. pacifica has a single nematotheca on the apophysis of the hydrotheca, no distinction between the apophysis and the pedicel of the hydrotheca, and much larger hydrothecae. As a result of this study, a total of two species belonging to genus Zygophylax have been reported in the hydrozoan fauna of Korea to date.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.483-495
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• 2011

In modern society, the range of time and space in life is continually expanding due to increase of income and diversification of life. In order to respond to these changes and to satisfy needs and to secure the mobility of citizens, the construction of transport infrastructure and public transport services should be provided continually. In particular, to ensure mobility during late-night hours, providing metropolitan public transport services is urgently needed. Due to expansion of life zone, tension of time and space of metropolitan transportation is essential to construct transport infrastructure in preparation for entry into 24-hour community. This study was based on analysis of travel resource and survey data conducted by passengers of express trains, conventional trains, and metropolitan bus. This study is to investigate use characteristics of passengers and characteristics and problems of Gyeongin-line. Moreover, this study's purpose is to suggest plans in order to improve express train operation and extend hours of the midnight express. It is also important to vitalize public transportation.

• Animal Systematics, Evolution and Diversity
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• 제37권4호
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• pp.335-339
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• 2021

In 2020, during a survey of cnidarian fauna around Chuja-do locating in the northern part of Jeju-do, Korea, several hydroids were collected from the subtidal zone by SCUBA diving. Through taxonomic examination, one unrecorded species, Hydrodendron stechowi Hirohito, 1995, was found in Korea. It was newly added to the list of Korean hydrozoan fauna. This species was discovered for the first time since its first report as a new species in Japan. Their vivid orange-colored colonies were attached to the sponge on rocky substrate between depths of 15 and 20 m. Thus, a total of five species belonging to genus Hydrodendron, including the species reported in this study, have been reported in Korean waters so far.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2006년도 추계학술발표대회 논문집
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• pp.438-442
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• 2006

The aims of this study was to identify the needs of a generation-integrated housing complex by respondents with different generations and propose the plans for this type of low-rise housing complex. Respondents were needed a housing unit with 31-40 pyung, three rooms, and two baths. Also, they wanted to live a housing complex with size of 50-100 housing units, providing community services such as green zone and rivulet, community programs and spaces, and residents gathering public spaces. The proposed plans showed three types of standard housing unit plans and three modified housing unit plans to accommodate the changing life cycle of the family.

• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3517-3527
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• 2021

New 80-MW (electric) ultra-long-life sodium cooled fast reactor core having inherent safety characteristics is designed with heterogeneous fuel assemblies comprised of driver and blanket fuel rods. Several options using upper sodium plenum and SSFZ (Special Sodium Flowing Zone) for reducing sodium void reactivity are neutronically analyzed in this core concept in order to improve the inherent safety of the core. The SSFZ allowing the coolant flow from the peripheral fuel assemblies increases the neutron leakage under coolant expansion or voiding. The Monte Carlo calculations were used to design the cores and analyze their physics characteristics with heterogeneous models. The results of the design and analyses show that the final core design option has a small burnup reactivity swing of 618 pcm over ~54 EFPYs cycle length and a very small sodium void worth of ~35pcm at EOC (End of Cycle), which leads to the satisfaction of all the conditions for inherent safety with large margin based on the quasi-static reactivity balance analysis under ATWS (Anticipated Transient Without Scram).