• Journal of Korea Foundry Society
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• v.43 no.4
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• pp.187-193
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• 2023

Shell core making is an excellent process in terms of formability and desanding, but when the molten aluminum comes into con- tact with the shell core, gas generation by pyrolysis of the resin is inevitable. In addition, when the ventilation is inadequate, pores will remain inside the casting, which can directly lead to defects of the casting. While studies on the gas generation behavior of shell core making have been reported, the modeling of gas generation has not been extensively investigated. We will develop a gas evolution analysis method that considers the relationship between temperature and gas quantity for the core to be developed. We then use the developed method to analyze the flow and solidification behavior of metal molten metal during core mold design and low-pressure casting of cylinder head products, and predict the occurrence of casting defects to derive a casting method that min- imizes the occurrence of defects.

• Journal of The Korean Society of Clinical Toxicology
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• v.15 no.1
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• pp.65-67
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• 2017

Even though Neptunea contricta appears similar to Batilus cornutus and Rapana venosa, they are different in tetramine content which inhibits the neuronal calcium channel. Therefore, mistaking Neptunea contricta for Batilus cornutus or Rapana venosa, can result in the occurrence of toxic symptoms. Three patients developed nausea, epigastric pain, chest pain, dizziness, blurred vision, dyspnea, hypertension and tachycardia after eating Neptunea contricta. Moreover, consumption of one only piece was sufficient to cause symptoms because each Neptunea contricta has 17.3 mg of tetramine. Accordingly, care should be taken when patients are consuming more than 5 pieces because toxic symptoms such as dyspnea can occur. Moreover, correct species identification is important because the quantity of tetramine varies among sea snail species. Finally, it is important to educate people to remove the salivary glands completely before consuming Neptunea contricta.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.1
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• pp.64-71
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• 2010

As the ultimate goal of the Aeronautical communication is delivery of information, it is essential to communicate via accurate use of language; there are possibilities of errors occurring as the exchange of information between pilot and air traffic controller is conducted through radio communication. Especially, there are frequently reported errors in radio communication in the event that two or more aircrafts using similar call-signs are operated in one sector. In this paper, a list of errors, which can possibly caused by air traffic controllers when controlling airplanes using similar call-signs, was derived through preceding researches and theories related to similar call-signs and human errors. Based on this list, an experiment was conducted on 52 air traffic controllers working at "J" international airport. For this experiment, ATC2K which is a simulated approach control radar developed in Korea, was used; and a regression formula was derived by analyzing the quantity of frequency change in error occurrence when controlling two or more airplanes using similar call-signs base on a premeditated scenario.The data presented in this research has useful findings and concepts for understanding the errors that can possibly occur while controlling airplanes using similar call-signs.

• Journal of Ecology and Environment
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• v.33 no.1
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• pp.19-22
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• 2010

Migratory birds, by crossing significant ecological barriers, carry and may subsequently introduce exotic seeds into new ecological zones during period of migration. The study of epizoochory, which includes seed dispersal by adhesion to bird feathers, has been relatively neglected compared to the study of seed dispersal by frugivores. To determine whether exotic seeds are being imported to stopover islands by migrating birds, and to estimate the quantity of seeds of exotic species being introduced, we examined migratory birds that were captured in mist nets for attached exotic plant diaspores in 2008 and 2009 on Hongdo Island, Korea. From a total of 3,947 birds examined, we found exotic seeds of Japanese Chaff Flowers (Achyranthes japonica) attached to three species of migratory birds (0.08%; Eurasian Bittern Botaurus stellaris, Swinhoe's Rail Coturnicops exquisitus and Oriental Turtle Dove Streptopelia orientalis). Despite the low occurrence of A. japonica seeds on the external parts of birds, the results suggest that migratory birds may be potential dispersing agents for A. japonica, a species that is currently threatening native ecosystems on many islands in Korea.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2089-2098
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• 2015

With the continuous development in insulation of electrical equipment design, the reliability of the system has been enhanced. However, in the manufacturing process and during operation under continues stresses introduce local defects, such as voids between interfaces that can responsible to occurrence of partial discharge (PD), electric field distortion and accumulation of charges. These defects may lead to localize corrosion and material degradation of insulation system, and a serious threat to the equipment. A model of three layers of PI film with air gap is presented to understand the influence of interface and voids on exploitation conditions such as strong electrical field, PD activity and charge movement. The analytical analysis, and experimental results are good agreement and show that the lose contact between interfaces accumulate more residual charges and in consequences increase the electric field intensity and accelerates internal discharges. These residual charges are trapped charges, injected by the electrodes has often same polarity, so the electric field in cavities increases significantly and thus partial discharge inception voltage (PDIV) decreases. Contrary, number of PD discharge quantity increases due to interface. Interfacial polarization effect has opposite impact on electric field and PDIV as compare to void.

• Steel and Composite Structures
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• v.19 no.4
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• pp.939-952
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• 2015

In this paper, brake pad performance of two organic matrix composites namely, Sample 1 (contains no brass filler) and Sample 2 (contains 1.5% brass filler), is studied based on tribological and squeal noise behavior. In the first stage, a pin-on-disc tribometer is used to evaluate the frictional behavior of the two pads. On the following stage, these pads are tested on squeal noise occurrence using a drag-type brake dynamometer. From the two type of tests, the results show that; (i) brass fillers play a dual role; firstly as reinforcing element of the brake pad providing primary contact sites, and secondly as solid lubricant by contributing to the formation of a layer of granular material providing velocity accommodation between the pad and the disc; (ii) brass fillers contribute to friction force stabilization and smooth sliding behavior; (iii) the presence of small weight quantity of brass filler strongly contributes to squeal occurrences; (iv) there is close correlation between pin-on-disc tribometer and brake dynamometer tests in terms of tribological aspect.

• Journal of the military operations research society of Korea
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• v.36 no.2
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• pp.1-10
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• 2010

Learning rate is generally applied to estimate an appropriate production labor cost. Learning effect is obtained from repetitive work during the production period under 3 assumptions ; homogeneous production, same producer, quantity measure in continuous unit. However, production breaks occur frequently in Korean defense industry environment because of budget constraint and annual requirements. In this case previous learning effect can not be applied due to learning loss. This paper proposed the application of learning rate when a production break occurs in Korea defense industry. To obtain a learning loss, we surveyed various learning loss factors for different production breaks(6, 12, 18 months) from 4 defense industry companies. Then, we estimate the first unit labor hours in re-production phase after production break using Anderlohr method and Retrograde method with the result of the survey. This work is the first attempt to show a method which defines and evaluates the learning loss factors in Korean defense industry environment.

• New & Renewable Energy
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• v.5 no.2
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• pp.9-14
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• 2009

Automobile Shredder Residue (ASR) is very appropriate in a gasification melting system. Gasification melting system, because of high reaction temperature over than $1,350^{\circ}C$, can reduce harmful materials. To use the gasification processes for hydrogen production, the high concentration of CO in syngas must be converted into hydrogen gas by using water gas shift reaction. In this study, the characteristics of shift reaction of the high temperature catalyst (KATALCO 71-5M) and the low temperature catalyst (KATALCO 83-3X) in the fixed - bed reactor has been determined by using simulation gas which is equal with the syngas composition of gasification melting process. The carbon monoxide composition has been decreased as the WGS reaction temperature has increased. And the occurrence quantity of the hydrogen and the carbon dioxide increased. When using the high temperature catalyst, the carbon monoxide conversion ratio ($1-CO_{out}/CO_{in}$) rose up to 95.8 from 55.6. Compared with average conversion ratio from the identical synthesis gas composition, the low temperature catalyst was better than the high temperature catalyst.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.6_2
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• pp.665-672
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• 2012

Amid rapidly increasing imagery inputs and their volume in a remote sensing imagery database, Content-Based Image Retrieval (CBIR) is an effective tool to search for an image feature or image content of interest a user wants to retrieve. It seeks to capture salient features from a 'query' image, and then to locate other instances of image region having similar features elsewhere in the image database. For a CBIR approach that uses texture as a primary feature primitive, designing a texture descriptor to better represent image contents is a key to improve CBIR results. For this purpose, an extended feature vector combining the Gabor filter and co-occurrence histogram method is suggested and evaluated for quantitywise and qualitywise retrieval performance criterion. For the better CBIR performance, assessing similarity between high dimensional feature vectors is also a challenging issue. Therefore a number of distance metrics (i.e. L1 and L2 norm) is tried to measure closeness between two feature vectors, and its impact on retrieval result is analyzed. In this paper, experimental results are presented with several CBIR samples. The current results show that 1) the overall retrieval quantity and quality is improved by combining two types of feature vectors, 2) some feature is better retrieved by a specific feature vector, and 3) retrieval result quality (i.e. ranking of retrieved image tiles) is sensitive to an adopted similarity metric when the extended feature vector is employed.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.708-713
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• 2008

Various kinds of contaminant are generated from many kinds of interior construction materials, furniture and life articles. People of today living indoor most of the time are exposed to these kinds of contaminant. In this connection, people are exerting their efforts to reduce the occurrence of contaminant from the interior finish materials. And it is the actual condition that research is being actively made on the method of reducing contaminant by performing bake-out for newly constructed housings. Bake-out is the method of temporarily increasing the generation of the harmful contaminant quantity including VOCs and Formaldehyde emitting from construction materials or finish materials by increasing the interior temperature of the newly constructed buildings or improved or repaired buildings, and then removing it by mobilizing ventilation system. In this study, the researcher measured the effect of reduced concentration according to ventilation or non-ventilation of the newly constructed but not yet resident public housings during the bake-out in order to grasp the effect of reduced interior air contaminant according to the elapse of timeat the time of bake-out.