• Proceedings of the Korean Society of Applied Entomolohy Conference
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• 2005.05a
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• pp.98-98
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• 2005

• Journal of Drive and Control
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• v.14 no.1
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• pp.1-7
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• 2017

The power train of a concrete truck mixer reducer includes differential planetary gears to get a large reduction ratio for operating the mixer drum in a compact structure. These differential planetary gears are a very important part of the mixer reducer where strength problems are the main concern. Gear bending stress, gear compressive stress and scoring failure are the main concerns. Many failures in differential planetary gears are due to the insufficient gear strength and resonance problems caused by major excitation forces such as gear mating failure in the transmission. In the present study, where the excitation frequencies are the gear tooth passing frequencies of the mating gears, a Campbell diagram is used to calculate differential planetary gear critical speeds. Mode shapes and natural frequencies of the differential planetary gears are calculated by CATIA V5. These are used to predict gear resonance failures by comparing the working speed range with the critical speeds due to the gear transmission errors of the differential planetary gears.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.305-306
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• 2002

In this paper, the endurance life of the rolling bearings with defective balls and their failure (flaking) phenomena are presented. It was found that the lives of ball bearings with defective balls were shorter than that of calculated L10 life as well as that of normal bearings in spite of the using standard bearing components. Although the bearings were assembled with defective balls, whereas the other parts were qualified new ones, the main failures were occurred on the inner ring raceways. Moreover, the failures were on the center of the groove curvature and the severity of failure is similar to the order of initial defect depth of the balls. These shows that the defects on the bearings can affect the life of tribologically contacted mating parts.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.395-401
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• 2003

In this paper, the dent printing phenomena and critical dent size which lead to premature failure of deep grooved ball bearing for automobiles are presented. The results of newly assembled test bearings showed that the ball dent size strongly affect the bearing life and inner ring raceways were the major failed parts in spite of using the dented balls. The dent printing phenomena are a root cause of premature failure, which was not reported until now. And there exist the critical ball dent size for given rolling bearings and operating conditions. So, the initial condition of tribologically mating parts should be treated as important as the failed body itself.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.6
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• pp.868-870
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• 1999

A total of 69 ovaries were collected from 345 camels slaughtered in Maiduguri abattoir, North-Eastern part of Nigeria, to study the influence of season on ovary weight and corpus luteum count in the dromedary (single humped) camel (Camelus dromedaries). Right ovary was significantly heavier (p<0.01) and had more follicular fluid than the left. Although corpus luteum count increased gradually throughout the study period, no camel had 3 active corpora lutea and only 53 out of the total number had two. Ovarian activity seem to be higher in the cold dry harmattan season, November/December, than during the warmer post rainy season, September/October. These periods can be exploited by farmers, especially peasants who rely heavily on natural mating, to obtain greater conception rates and reduce the chance of failure during mating.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.3
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• pp.186-193
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• 2018

Modern manufacturing industries is to produce both precise and robust mechanical parts without failure while they are in service. In order to prevent a part failure for its lifetime, a mechanical design for a part should be examined on a basis of mechanical simulation. A nozzle plate, being a key part in steam engines, changes flow directions of steam in a turbine used in power plant. This paper is to the design and test for part safety and durability. Currently, nozzle plates are fabricated by welding nozzles to their plates. Welding causes some defects on the used materials while they are being manufactured. Another major defect is un-even pitches between welded nozzles. Welding causes phase changes because of high melting temperature of metal. This leads to decay on the welding spots, which weakens their structural strength and then, may lead to early damages on mechanical structures. This research proposes assembly-typed nozzle plate without welding. From the beginning, nozzle and plate are designed for insertion-typed assembly. Nozzle head and foot are designed in accordance with the grooves on outer ring and inner ring of a plate to make mating surfaces. Then the nozzle plate should be proved for structural and fatigue safety before they are put in manufacturing. This research adopts commercial softwares for modeling and mechanical simulation. The test result shows that the design with smaller mating area and deeper insertion produces higher safety in terms of structure and durability. From the conclusion, this paper proposes the assembly-typed nozzle plate to replace the welding typed.

• Journal of Drive and Control
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• v.14 no.4
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• pp.71-78
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• 2017

The power train of hydro-mechanical continuously variable transmission (HMCVT) for 8-ton class forklift includes hydro-static units, hydraulic multi-wet disc brake & clutches and complex helical & planetary gears. The helical & planetary gears are key components of HMCVT's power train wherein strength problems are the main concerns including gear bending stress, gear compressive stress, and scoring failure. Many failures in power train gears of HMCVT are due to the insufficient gear strength and resonance problems caused by major excitation forces, such as gear transmission error of mating gear fair in the transmission. In this study, wherein excitation frequencies are the gear tooth passing frequencies of the mating gears, a Campbell diagram is used to calculate the power train gears' critical speeds. Mode shapes and natural frequencies of the power train gears are calculated by CATIA V5. These are used to predict resonance failures by comparing the actual working speed range with the critical speeds due to the gear transmission errors of HMCVT's power train gears.

• Journal of Veterinary Clinics
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• v.17 no.1
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• pp.285-288
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• 2000

Nine immature 30-day-old female rats were injected sc at 0800 hr with pregnant mare serum gonadotrophin(PMSG) to induce ovulation and mating. Fifty-six hours later the animals were placed with mature male rats overnight (one female and one male). Five of 9 immature female rats treated with PMSG were pregnant and allowed to maintain the pregnancy to term. Three of 5 pregnant rats were failed to maintain pregnancy to term. Two of 5 pregnant rats seemed to be developed normally and increased abdominal enlargement as pregnancy progresses, but did not occurred parturition on day of 43 or 48 of pregnancy, respectively. On day 44 or 49, pregnant rats were killed and examined uterus and ovaries. There was no fetus but approximately 50∼60ml. of mucopurulent fluids were accumulated in the uterine cavity and 40 or 42 corpora lutea persisted in the ovaries. Pyometra was developed after coitus in PMSG-treated immature female rat.

• Journal of Embryo Transfer
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• v.24 no.3
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• pp.169-176
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• 2009

Domestic bitches are non-seasonally monoestrus; spontaneously ovulate only once or twice occurs at anytime of the year. Estrus induction has been applied infrequent estrus, misleading ovulation, mating difficulties, failure to conceive after normal mating, pregnancy failure and biological research. Protocol of estrus induction which included variable hormones such as FSH, GnRH, and PMSG have been applied for the last decades. Recently, Bromocriptine, one of anti-prolatin/dopamine agonist has been occasionally applied for estrus induction. The study was carried out to investigate the effective method for the induction of estrus in bitches using different hormone treatments, and the initiation time of estrus from hormone treatment by assessments of cytological observation and blood plasma progesterone concentration. A total of 54 bitches on anestrus were selected for the study and divided randomly into 8 treatment groups as follow. Control, natural estrus; FSH (L), FSH (1.5 mg/kg, twice a day, $Falltrophin^{(R)}$, Vetrepharm); FSH (H), FSH (3.0 mg/kg, twice a day); GnRH+FSH, GnRH (5 ug/kg, once first day, $GNADON^{(R)}$, Dongbang)+FSH (3 mg/kg, SID); PMSG, PMSG (50 IU/kg, every third day $FOLLIGON^{(R)}$, Intevet); GnRH+PMSG, GnRH (5 ug/kg, only first day)+PMSG (50 IU/kg, every third day); GnRH, GnRH (5 ug/kg, only first day); Bromocriptine, bromocriptine (0.3 mg/kg, SID, $Parlodel^{(R)}$, Novartis). The bitches were evaluated clinical sign, cytological exam and $OVUCHECK^{(R)}$ Premate for assessment of estrus induction. Estrus induction rates were significantly (P<0.05) higher in GnRH+PMSG (100%) compared to others. PMSG and GnRH+PMGS (87.5 and 100%) and Bromocriptine (77.8%) were higher than others except GnRH+PMSG. Analysis of vaginal smear has proved to be effective a correct assessment of estrus induction with assay of progesterone concentration by $OVUCHECK^{(R)}$ Premate. Proestrus initiated by the $6^{th}$ after induction in most case. In conclusion, bromocriptine is an effective drug for estrus induction in bitches and assay of progesterone concentration by $OVUCHECK^{(R)}$ Premate with examination of vaginal smear that should be useful to detection of estrus induction of estrus induced bitches.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.1-5
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• 2001

One of the major advantages of using engineering plastics is ease of part assembly through a locking mechanism known as a snap fit. The typical snap fit involves a short cantilever beam with a projection at the free end. which slides over a one way ramp on the mating part to lock in place. The tightness of the mechanism is determined by the lateral interference of the two sliding members If too small they become loose and can't hold together. while if too large. excessive force can be generated. causing failure of the cantilever beam during the assembly operation. Therefore. the accurate determination of the force-deflection relationship for cantilever beams is a key element in snap fit design. And also. the process of injection molding should be considered when cantilever beam is designed. But it is not easy for novice designers to design them appropriately because of the profound knowledge related to injection molding. In this paper. an intelligent design program has been developed and proposed to improve a conventional empirical design method.