• Magazine of the Korea Concrete Institute
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• v.19 no.4
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• pp.73-77
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• 2007

• Journal of the Korean Magnetics Society
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• v.26 no.3
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• pp.86-91
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• 2016

The cogging torque of a brushless dc (BLDC) motor results from the interaction between permanent magnets and iron core, and it causes noise and induce vibrations. During a manufacturing process, assembly tolerances lead to the change of the electromagnetic structure of a BLDC motor where permanent magnets are not properly glued to the surface of rotor core. In this paper, the effect of magnet separation from the surface of rotor core on the cogging torque is investigated due to assembly tolerance. The relationship with key design parameters is considered such as separation between magnets and rotor core, the number of magnets having separation, as well as the several types of arrangements among neighboring magnets. Finite element method (FEM) has been used to analyze a BLDC motor, and the allowable assembly tolerance is proposed to prevent generating noise and vibrations. Within proposed assembly tolerance, it is concluded that the cogging torque of a BLDC motor is decreased, and hence noise and vibrations.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.3
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• pp.276-283
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• 2011

The growth and tolerance for water temperature and salinity were compared among red sea bream Pagrus major (RSB) black sea bream Acanthopagrus schregeli (BSB) and their hybrid ($F_1$), female RSB ${\times}$ male BSB. The growth of the $F_1$ fish did not differ until 27 days after hatching (dAH), after which the most rapid growth was observed until approximately 300 dAH, followed by RSB and BSB. However, the RSB had out grown the $F_1$ fish by approximately 303 dAH. By 480 dAH, the RSB were largest, followed by the $F_1$ and BSB groups. The tolerances for high and low water temperature were significantly different for each species and growth stage. The largest tolerance spectrum was observed in the BSB group, and the tolerance spectrums gradually decreased with increasing final body weight. During the salinity tolerance trials, all of the species started to die following transfer into freshwater (0 psu). BSB showed the highest survival rate when kept in fresh water for an average of 29.9 hours, while the $F_1$ fish were more tolerant than the RSB fish. The fish were increasingly tolerant to fresh water and changes in water temperature as they grew, while the size of the temperature spectrum remained unchanged but shifted to a lower temperature range with growth. Our results demonstrate that $F_1$ performed well in terms of growth compared to parental fish, with higher temperature and salinity tolerances than RSB, and is thus suggested to be a suitable aquaculture species for Korea and northeast China.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.219.1-219.1
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• 2005

• Journal of Korean Society for Quality Management
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• v.20 no.1
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• pp.107-117
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• 1992

Conventional fault tree analysis has several problems as the estimations and tolerances of the failure probability values. To overcome these problems, fuzzy concepts with natural language can be applied to conventional fault tree analysis. And, we propose the evaluation method of the imprecision of top/basic events and possibility importances of basic events.

• Proceedings of the Turfgrass Society of Korea Conference
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• 2005.04a
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• pp.13-15
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• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.917-918
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• 2011

• Journal of the Korean Society for Precision Engineering
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• v.29 no.8
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• pp.879-886
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• 2012

The ultrasonic horn used for bonding of flip chip has been designed to vibrate at a natural frequency. The ultrasonic horn must be manufactured accurately in physical terms, because the small change of mechanical properties may result in the significant change of natural frequency. Therefore, tight tolerance is inevitable to keep the natural frequency in acceptable range. However, since tightening of the tolerance increases the manufacturing cost significantly, trade-off between the cost and accuracy is necessary. In this research, an attempt was made to design the ultra sonic horn within acceptable natural frequency while the manufacturing cost was kept as low as possible. For this purpose, among the 18 tolerances of physical terms of the ultrasonic horn, the most important 4 factors were selected using Taguchi method. The equation to relate those main factors and the natural frequency was made using response surface method. Finally, optimal design scheme for minimum manufacturing cost without a loss of performance was determined using SQP method.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.67-72
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• 2011

The main objective of this paper is obtaining the optimal carburizing hours which impacts geometric tolerances, OPD(Over Pin Diameter), runout, hardness and fatigure strength of SCM415 spur gear. In order to observe the deformation of the gear, the circularity, squareness, OPD(Over Pin Diameter) and runout were measured at 3hour, 4hour and 5hour respectively. As the result, the 3hour situation is the best, which very similar with the 4hour one. Afterwards, with the purpose of getting the result of gear hardness, the surface hardness, maximum hardness and interior hardness were measured. The result is 5h situation is the best, and it's similar with 4hour one. At last, the fatigue tests have been done which receive the result that the 4h situation showed 9~12% fatigue strength improvement compared with the 3h and 5h ones. To sum up the results, the 4hour situation shows the best performance in accuracy, hardness and fatigue strength.

• Korean Journal of Environmental Agriculture
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• v.14 no.3
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• pp.351-373
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• 1995

The objective of this paper is to present relevant information and data from domestic and foreign references and to propose legal standards on pesticide residues in order to mitigate the pesticide contamination in the water environment. Among 200 pesticide ingredients in use in Korea, items necessary for standard setting were selected and theoretical residue limits were computed. The results are summarized as follows. In advanced countries, drinking water standards are established on the basis of health index ADI and water intake, whereas standards for surface water are established temporarily on the basis of different parameters, inconsistent with different countries. Pesticide residue limits applicable in Korea were proposed for 24 pesticides in drinking water(health basis) and for 25 pesticides in surface water(ecotoxicological basis), as selected by risk priority. It was recommended to accumulate scientific data by persistent research efforts in order to maintain the justification of the pesticide residue limits in water and relevant research topics to be undertaken in future were proposed.