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유선재,김석현 江原大學校 産業技術硏究所 1990 産業技術硏究 Vol.10 No.-
Car body resonance often generates severe vibrational and noise problems in vehicle compartment. In this study, vibrational characteristics of 2-D vehicle compartment model is investigated and structural modification is carried out by numerical simulation to shift natural frequencies and to reduce stresses in resonance. To this end, ring models of the compartment are manufactured and analysed by FEA. The results are verified to be in good agreement with those of experimental modal testing. And the results of this study offer efficient structural modification technique for vibration reduction of real cars.
김석현 한국잔디학회 2004 한국잔디학회지 Vol.18 No.1
The efficient refinement of seed is required to reduce the cost and labor input in artificial propagation of wild plant. This study was carried out to develop methods for collecting and refining tiny seeds from wild plants. For obtaining Phragmites communis seeds, the inflorescence was cut into small fragments using a Straw Cutter and subsequently detached pappus hairs from seed coat by Hammer Mill. The primary refined seeds were passed 1.0 mm sieve. The screened seeds were subjected to Seed Blower with wind speed of 0.25 mㆍsec-1 to collected intact and well-ripen seeds. The seeds of Imperata cylindrica were refined as follows. Inflorescences were cut using a Straw Cutter first. The pappus was removed from cut fragments using a Hammer Mill and subsequently subjected to Seed Scarifier at 500rpm for 60 sec. for further separation. The separated seeds were passed 1.0 mm screen and collected after blowing with Seed Blower of wind speed of 0.15 mㆍsec-1. When the amount of seed was too little to refine with Seed Scarifier and Blower, the procedure was slightly modified from the procedure described above. The crude seed mixture obtained from Hammer Mill step was hand-refined roughly and then immersed into cone. (95%) sulfuric acid for 2 min. and collected floating portion after dilution of sulfuric acid solution 100 times with tap water. The collected seeds were dried and passed 0.149 mm sieve. During seed refining process using mechanical or sulfuric acid treatments, a small portion of damaged seed were evolved, however, the amount was not noticeable as compared to the total amount of collected seeds. Because the germination percentages between hand-refined seeds and seeds refined by above methods were not statistically different, the developed procedures for refining tiny seed of wild plants are helpful to reduce the cost and labor input in artificial propagation of two species.
뇌척수액루가 동반된 전두사골 점액농류 조대술 후 발생한 긴장성 기뇌증 1례
김석현,정재훈,문수진,노환중 대한비과학회 2018 Journal of rhinology Vol.25 No.1
After the trauma of frontoethmoidal sinus, post-traumatic mucocele may occur. Surgical removal of the lesions rarely produces cerebrospinal fluid (CSF) leakage and even delayed tension pneumocephalus. We experienced a case of fronto-ethmoid mucocele complicated with peri-operative CSF leakage and post-operative tension pneumocephalus which was improved by conservative treatment. It is imperative to take into account the potential for tension pneumocephalus when a patient suffers from severe headache after sinus surgery.
김석현,김태형,김윤호,한영호 강원대학교 산업기술연구소 2006 産業技術硏究 Vol.26 No.A
The Chun-cheon Citizen's Bell was cast in memory of hosting the 2010 world leasure conference and a striking ceremony was held at the city hall on December 31, 2005. In this study, vibration and sound of the bell are measured and the property of the magnificent sound of the bell is scientifically investigated. Frequency components making the sound are identified and how the frequency components decrease with time is observed using waterfall plot(3-dimensional frequency spectrum). Beat characteristics of the hum(1st frequency) and the fundamental(2nd frequency)are examined by experiment. Directivity of the sound radiation of the bell is examined by measuring the vibration and sound in several directions. Duration of the vibration and the sound is estimated using damping ratio.